linux/fs/block_dev.c

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/*
* linux/fs/block_dev.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
*/
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/fcntl.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/device_cgroup.h>
#include <linux/highmem.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/blkpg.h>
#include <linux/buffer_head.h>
#include <linux/pagevec.h>
#include <linux/writeback.h>
#include <linux/mpage.h>
#include <linux/mount.h>
#include <linux/uio.h>
#include <linux/namei.h>
#include <linux/log2.h>
#include <linux/kmemleak.h>
#include <asm/uaccess.h>
#include "internal.h"
struct bdev_inode {
struct block_device bdev;
struct inode vfs_inode;
};
static const struct address_space_operations def_blk_aops;
static inline struct bdev_inode *BDEV_I(struct inode *inode)
{
return container_of(inode, struct bdev_inode, vfs_inode);
}
inline struct block_device *I_BDEV(struct inode *inode)
{
return &BDEV_I(inode)->bdev;
}
EXPORT_SYMBOL(I_BDEV);
/*
* move the inode from it's current bdi to the a new bdi. if the inode is dirty
* we need to move it onto the dirty list of @dst so that the inode is always
* on the right list.
*/
static void bdev_inode_switch_bdi(struct inode *inode,
struct backing_dev_info *dst)
{
spin_lock(&inode_lock);
inode->i_data.backing_dev_info = dst;
if (inode->i_state & I_DIRTY)
list_move(&inode->i_wb_list, &dst->wb.b_dirty);
spin_unlock(&inode_lock);
}
static sector_t max_block(struct block_device *bdev)
{
sector_t retval = ~((sector_t)0);
loff_t sz = i_size_read(bdev->bd_inode);
if (sz) {
unsigned int size = block_size(bdev);
unsigned int sizebits = blksize_bits(size);
retval = (sz >> sizebits);
}
return retval;
}
/* Kill _all_ buffers and pagecache , dirty or not.. */
static void kill_bdev(struct block_device *bdev)
{
if (bdev->bd_inode->i_mapping->nrpages == 0)
return;
invalidate_bh_lrus();
truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
}
int set_blocksize(struct block_device *bdev, int size)
{
/* Size must be a power of two, and between 512 and PAGE_SIZE */
if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
return -EINVAL;
/* Size cannot be smaller than the size supported by the device */
if (size < bdev_logical_block_size(bdev))
return -EINVAL;
/* Don't change the size if it is same as current */
if (bdev->bd_block_size != size) {
sync_blockdev(bdev);
bdev->bd_block_size = size;
bdev->bd_inode->i_blkbits = blksize_bits(size);
kill_bdev(bdev);
}
return 0;
}
EXPORT_SYMBOL(set_blocksize);
int sb_set_blocksize(struct super_block *sb, int size)
{
if (set_blocksize(sb->s_bdev, size))
return 0;
/* If we get here, we know size is power of two
* and it's value is between 512 and PAGE_SIZE */
sb->s_blocksize = size;
sb->s_blocksize_bits = blksize_bits(size);
return sb->s_blocksize;
}
EXPORT_SYMBOL(sb_set_blocksize);
int sb_min_blocksize(struct super_block *sb, int size)
{
int minsize = bdev_logical_block_size(sb->s_bdev);
if (size < minsize)
size = minsize;
return sb_set_blocksize(sb, size);
}
EXPORT_SYMBOL(sb_min_blocksize);
static int
blkdev_get_block(struct inode *inode, sector_t iblock,
struct buffer_head *bh, int create)
{
if (iblock >= max_block(I_BDEV(inode))) {
if (create)
return -EIO;
/*
* for reads, we're just trying to fill a partial page.
* return a hole, they will have to call get_block again
* before they can fill it, and they will get -EIO at that
* time
*/
return 0;
}
bh->b_bdev = I_BDEV(inode);
bh->b_blocknr = iblock;
set_buffer_mapped(bh);
return 0;
}
static int
blkdev_get_blocks(struct inode *inode, sector_t iblock,
struct buffer_head *bh, int create)
{
sector_t end_block = max_block(I_BDEV(inode));
unsigned long max_blocks = bh->b_size >> inode->i_blkbits;
if ((iblock + max_blocks) > end_block) {
max_blocks = end_block - iblock;
if ((long)max_blocks <= 0) {
if (create)
return -EIO; /* write fully beyond EOF */
/*
* It is a read which is fully beyond EOF. We return
* a !buffer_mapped buffer
*/
max_blocks = 0;
}
}
bh->b_bdev = I_BDEV(inode);
bh->b_blocknr = iblock;
bh->b_size = max_blocks << inode->i_blkbits;
if (max_blocks)
set_buffer_mapped(bh);
return 0;
}
static ssize_t
blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
loff_t offset, unsigned long nr_segs)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
return __blockdev_direct_IO(rw, iocb, inode, I_BDEV(inode), iov, offset,
nr_segs, blkdev_get_blocks, NULL, NULL, 0);
}
int __sync_blockdev(struct block_device *bdev, int wait)
{
if (!bdev)
return 0;
if (!wait)
return filemap_flush(bdev->bd_inode->i_mapping);
return filemap_write_and_wait(bdev->bd_inode->i_mapping);
}
/*
* Write out and wait upon all the dirty data associated with a block
* device via its mapping. Does not take the superblock lock.
*/
int sync_blockdev(struct block_device *bdev)
{
return __sync_blockdev(bdev, 1);
}
EXPORT_SYMBOL(sync_blockdev);
/*
* Write out and wait upon all dirty data associated with this
* device. Filesystem data as well as the underlying block
* device. Takes the superblock lock.
*/
int fsync_bdev(struct block_device *bdev)
{
struct super_block *sb = get_super(bdev);
if (sb) {
int res = sync_filesystem(sb);
drop_super(sb);
return res;
}
return sync_blockdev(bdev);
}
EXPORT_SYMBOL(fsync_bdev);
/**
* freeze_bdev -- lock a filesystem and force it into a consistent state
* @bdev: blockdevice to lock
*
* If a superblock is found on this device, we take the s_umount semaphore
* on it to make sure nobody unmounts until the snapshot creation is done.
* The reference counter (bd_fsfreeze_count) guarantees that only the last
* unfreeze process can unfreeze the frozen filesystem actually when multiple
* freeze requests arrive simultaneously. It counts up in freeze_bdev() and
* count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze
* actually.
*/
struct super_block *freeze_bdev(struct block_device *bdev)
{
struct super_block *sb;
int error = 0;
mutex_lock(&bdev->bd_fsfreeze_mutex);
if (++bdev->bd_fsfreeze_count > 1) {
/*
* We don't even need to grab a reference - the first call
* to freeze_bdev grab an active reference and only the last
* thaw_bdev drops it.
*/
sb = get_super(bdev);
drop_super(sb);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return sb;
}
sb = get_active_super(bdev);
if (!sb)
goto out;
error = freeze_super(sb);
if (error) {
deactivate_super(sb);
bdev->bd_fsfreeze_count--;
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return ERR_PTR(error);
}
deactivate_super(sb);
out:
sync_blockdev(bdev);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return sb; /* thaw_bdev releases s->s_umount */
}
EXPORT_SYMBOL(freeze_bdev);
/**
* thaw_bdev -- unlock filesystem
* @bdev: blockdevice to unlock
* @sb: associated superblock
*
* Unlocks the filesystem and marks it writeable again after freeze_bdev().
*/
int thaw_bdev(struct block_device *bdev, struct super_block *sb)
{
int error = -EINVAL;
mutex_lock(&bdev->bd_fsfreeze_mutex);
if (!bdev->bd_fsfreeze_count)
goto out;
error = 0;
if (--bdev->bd_fsfreeze_count > 0)
goto out;
if (!sb)
goto out;
error = thaw_super(sb);
if (error) {
bdev->bd_fsfreeze_count++;
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return error;
}
out:
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return 0;
}
EXPORT_SYMBOL(thaw_bdev);
static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
{
return block_write_full_page(page, blkdev_get_block, wbc);
}
static int blkdev_readpage(struct file * file, struct page * page)
{
return block_read_full_page(page, blkdev_get_block);
}
static int blkdev_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
return block_write_begin(mapping, pos, len, flags, pagep,
blkdev_get_block);
}
static int blkdev_write_end(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata)
{
int ret;
ret = block_write_end(file, mapping, pos, len, copied, page, fsdata);
unlock_page(page);
page_cache_release(page);
return ret;
}
/*
* private llseek:
* for a block special file file->f_path.dentry->d_inode->i_size is zero
* so we compute the size by hand (just as in block_read/write above)
*/
static loff_t block_llseek(struct file *file, loff_t offset, int origin)
{
struct inode *bd_inode = file->f_mapping->host;
loff_t size;
loff_t retval;
mutex_lock(&bd_inode->i_mutex);
size = i_size_read(bd_inode);
switch (origin) {
case 2:
offset += size;
break;
case 1:
offset += file->f_pos;
}
retval = -EINVAL;
if (offset >= 0 && offset <= size) {
if (offset != file->f_pos) {
file->f_pos = offset;
}
retval = offset;
}
mutex_unlock(&bd_inode->i_mutex);
return retval;
}
int blkdev_fsync(struct file *filp, int datasync)
{
fs/block_dev.c: fix performance regression in O_DIRECT|O_SYNC writes to block devices We are seeing a large regression in database performance on recent kernels. The database opens a block device with O_DIRECT|O_SYNC and a number of threads write to different regions of the file at the same time. A simple test case is below. I haven't defined DEVICE since getting it wrong will destroy your data :) On an 3 disk LVM with a 64k chunk size we see about 17MB/sec and only a few threads in IO wait: procs -----io---- -system-- -----cpu------ r b bi bo in cs us sy id wa st 0 3 0 16170 656 2259 0 0 86 14 0 0 2 0 16704 695 2408 0 0 92 8 0 0 2 0 17308 744 2653 0 0 86 14 0 0 2 0 17933 759 2777 0 0 89 10 0 Most threads are blocking in vfs_fsync_range, which has: mutex_lock(&mapping->host->i_mutex); err = fop->fsync(file, dentry, datasync); if (!ret) ret = err; mutex_unlock(&mapping->host->i_mutex); commit 148f948ba877f4d3cdef036b1ff6d9f68986706a (vfs: Introduce new helpers for syncing after writing to O_SYNC file or IS_SYNC inode) offers some explanation of what is going on: Use these new helpers for syncing from generic VFS functions. This makes O_SYNC writes to block devices acquire i_mutex for syncing. If we really care about this, we can make block_fsync() drop the i_mutex and reacquire it before it returns. Thanks Jan for such a good commit message! As well as dropping i_mutex, Christoph suggests we should remove the call to sync_blockdev(): > sync_blockdev is an overcomplicated alias for filemap_write_and_wait on > the block device inode, which is exactly what we did just before calling > into ->fsync The patch below incorporates both suggestions. With it the testcase improves from 17MB/s to 68M/sec: procs -----io---- -system-- -----cpu------ r b bi bo in cs us sy id wa st 0 7 0 65536 1000 3878 0 0 70 30 0 0 34 0 69632 1016 3921 0 1 46 53 0 0 57 0 69632 1000 3921 0 0 55 45 0 0 53 0 69640 754 4111 0 0 81 19 0 Testcase: #define _GNU_SOURCE #include <stdio.h> #include <pthread.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #define NR_THREADS 64 #define BUFSIZE (64 * 1024) #define DEVICE "/dev/mapper/XXXXXX" #define ALIGN(VAL, SIZE) (((VAL)+(SIZE)-1) & ~((SIZE)-1)) static int fd; static void *doit(void *arg) { unsigned long offset = (long)arg; char *b, *buf; b = malloc(BUFSIZE + 1024); buf = (char *)ALIGN((unsigned long)b, 1024); memset(buf, 0, BUFSIZE); while (1) pwrite(fd, buf, BUFSIZE, offset); } int main(int argc, char *argv[]) { int flags = O_RDWR|O_DIRECT; int i; unsigned long offset = 0; if (argc > 1 && !strcmp(argv[1], "O_SYNC")) flags |= O_SYNC; fd = open(DEVICE, flags); if (fd == -1) { perror("open"); exit(1); } for (i = 0; i < NR_THREADS-1; i++) { pthread_t tid; pthread_create(&tid, NULL, doit, (void *)offset); offset += BUFSIZE; } doit((void *)offset); return 0; } Signed-off-by: Anton Blanchard <anton@samba.org> Acked-by: Jan Kara <jack@suse.cz> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-04-23 17:18:06 +00:00
struct inode *bd_inode = filp->f_mapping->host;
struct block_device *bdev = I_BDEV(bd_inode);
int error;
fs/block_dev.c: fix performance regression in O_DIRECT|O_SYNC writes to block devices We are seeing a large regression in database performance on recent kernels. The database opens a block device with O_DIRECT|O_SYNC and a number of threads write to different regions of the file at the same time. A simple test case is below. I haven't defined DEVICE since getting it wrong will destroy your data :) On an 3 disk LVM with a 64k chunk size we see about 17MB/sec and only a few threads in IO wait: procs -----io---- -system-- -----cpu------ r b bi bo in cs us sy id wa st 0 3 0 16170 656 2259 0 0 86 14 0 0 2 0 16704 695 2408 0 0 92 8 0 0 2 0 17308 744 2653 0 0 86 14 0 0 2 0 17933 759 2777 0 0 89 10 0 Most threads are blocking in vfs_fsync_range, which has: mutex_lock(&mapping->host->i_mutex); err = fop->fsync(file, dentry, datasync); if (!ret) ret = err; mutex_unlock(&mapping->host->i_mutex); commit 148f948ba877f4d3cdef036b1ff6d9f68986706a (vfs: Introduce new helpers for syncing after writing to O_SYNC file or IS_SYNC inode) offers some explanation of what is going on: Use these new helpers for syncing from generic VFS functions. This makes O_SYNC writes to block devices acquire i_mutex for syncing. If we really care about this, we can make block_fsync() drop the i_mutex and reacquire it before it returns. Thanks Jan for such a good commit message! As well as dropping i_mutex, Christoph suggests we should remove the call to sync_blockdev(): > sync_blockdev is an overcomplicated alias for filemap_write_and_wait on > the block device inode, which is exactly what we did just before calling > into ->fsync The patch below incorporates both suggestions. With it the testcase improves from 17MB/s to 68M/sec: procs -----io---- -system-- -----cpu------ r b bi bo in cs us sy id wa st 0 7 0 65536 1000 3878 0 0 70 30 0 0 34 0 69632 1016 3921 0 1 46 53 0 0 57 0 69632 1000 3921 0 0 55 45 0 0 53 0 69640 754 4111 0 0 81 19 0 Testcase: #define _GNU_SOURCE #include <stdio.h> #include <pthread.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #define NR_THREADS 64 #define BUFSIZE (64 * 1024) #define DEVICE "/dev/mapper/XXXXXX" #define ALIGN(VAL, SIZE) (((VAL)+(SIZE)-1) & ~((SIZE)-1)) static int fd; static void *doit(void *arg) { unsigned long offset = (long)arg; char *b, *buf; b = malloc(BUFSIZE + 1024); buf = (char *)ALIGN((unsigned long)b, 1024); memset(buf, 0, BUFSIZE); while (1) pwrite(fd, buf, BUFSIZE, offset); } int main(int argc, char *argv[]) { int flags = O_RDWR|O_DIRECT; int i; unsigned long offset = 0; if (argc > 1 && !strcmp(argv[1], "O_SYNC")) flags |= O_SYNC; fd = open(DEVICE, flags); if (fd == -1) { perror("open"); exit(1); } for (i = 0; i < NR_THREADS-1; i++) { pthread_t tid; pthread_create(&tid, NULL, doit, (void *)offset); offset += BUFSIZE; } doit((void *)offset); return 0; } Signed-off-by: Anton Blanchard <anton@samba.org> Acked-by: Jan Kara <jack@suse.cz> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-04-23 17:18:06 +00:00
/*
* There is no need to serialise calls to blkdev_issue_flush with
* i_mutex and doing so causes performance issues with concurrent
* O_SYNC writers to a block device.
*/
mutex_unlock(&bd_inode->i_mutex);
error = blkdev_issue_flush(bdev, GFP_KERNEL, NULL);
if (error == -EOPNOTSUPP)
error = 0;
fs/block_dev.c: fix performance regression in O_DIRECT|O_SYNC writes to block devices We are seeing a large regression in database performance on recent kernels. The database opens a block device with O_DIRECT|O_SYNC and a number of threads write to different regions of the file at the same time. A simple test case is below. I haven't defined DEVICE since getting it wrong will destroy your data :) On an 3 disk LVM with a 64k chunk size we see about 17MB/sec and only a few threads in IO wait: procs -----io---- -system-- -----cpu------ r b bi bo in cs us sy id wa st 0 3 0 16170 656 2259 0 0 86 14 0 0 2 0 16704 695 2408 0 0 92 8 0 0 2 0 17308 744 2653 0 0 86 14 0 0 2 0 17933 759 2777 0 0 89 10 0 Most threads are blocking in vfs_fsync_range, which has: mutex_lock(&mapping->host->i_mutex); err = fop->fsync(file, dentry, datasync); if (!ret) ret = err; mutex_unlock(&mapping->host->i_mutex); commit 148f948ba877f4d3cdef036b1ff6d9f68986706a (vfs: Introduce new helpers for syncing after writing to O_SYNC file or IS_SYNC inode) offers some explanation of what is going on: Use these new helpers for syncing from generic VFS functions. This makes O_SYNC writes to block devices acquire i_mutex for syncing. If we really care about this, we can make block_fsync() drop the i_mutex and reacquire it before it returns. Thanks Jan for such a good commit message! As well as dropping i_mutex, Christoph suggests we should remove the call to sync_blockdev(): > sync_blockdev is an overcomplicated alias for filemap_write_and_wait on > the block device inode, which is exactly what we did just before calling > into ->fsync The patch below incorporates both suggestions. With it the testcase improves from 17MB/s to 68M/sec: procs -----io---- -system-- -----cpu------ r b bi bo in cs us sy id wa st 0 7 0 65536 1000 3878 0 0 70 30 0 0 34 0 69632 1016 3921 0 1 46 53 0 0 57 0 69632 1000 3921 0 0 55 45 0 0 53 0 69640 754 4111 0 0 81 19 0 Testcase: #define _GNU_SOURCE #include <stdio.h> #include <pthread.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #define NR_THREADS 64 #define BUFSIZE (64 * 1024) #define DEVICE "/dev/mapper/XXXXXX" #define ALIGN(VAL, SIZE) (((VAL)+(SIZE)-1) & ~((SIZE)-1)) static int fd; static void *doit(void *arg) { unsigned long offset = (long)arg; char *b, *buf; b = malloc(BUFSIZE + 1024); buf = (char *)ALIGN((unsigned long)b, 1024); memset(buf, 0, BUFSIZE); while (1) pwrite(fd, buf, BUFSIZE, offset); } int main(int argc, char *argv[]) { int flags = O_RDWR|O_DIRECT; int i; unsigned long offset = 0; if (argc > 1 && !strcmp(argv[1], "O_SYNC")) flags |= O_SYNC; fd = open(DEVICE, flags); if (fd == -1) { perror("open"); exit(1); } for (i = 0; i < NR_THREADS-1; i++) { pthread_t tid; pthread_create(&tid, NULL, doit, (void *)offset); offset += BUFSIZE; } doit((void *)offset); return 0; } Signed-off-by: Anton Blanchard <anton@samba.org> Acked-by: Jan Kara <jack@suse.cz> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-04-23 17:18:06 +00:00
mutex_lock(&bd_inode->i_mutex);
return error;
}
EXPORT_SYMBOL(blkdev_fsync);
/*
* pseudo-fs
*/
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock);
static struct kmem_cache * bdev_cachep __read_mostly;
static struct inode *bdev_alloc_inode(struct super_block *sb)
{
struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, GFP_KERNEL);
if (!ei)
return NULL;
return &ei->vfs_inode;
}
static void bdev_destroy_inode(struct inode *inode)
{
struct bdev_inode *bdi = BDEV_I(inode);
kmem_cache_free(bdev_cachep, bdi);
}
static void init_once(void *foo)
{
struct bdev_inode *ei = (struct bdev_inode *) foo;
struct block_device *bdev = &ei->bdev;
memset(bdev, 0, sizeof(*bdev));
mutex_init(&bdev->bd_mutex);
INIT_LIST_HEAD(&bdev->bd_inodes);
INIT_LIST_HEAD(&bdev->bd_list);
#ifdef CONFIG_SYSFS
INIT_LIST_HEAD(&bdev->bd_holder_list);
#endif
inode_init_once(&ei->vfs_inode);
/* Initialize mutex for freeze. */
mutex_init(&bdev->bd_fsfreeze_mutex);
}
static inline void __bd_forget(struct inode *inode)
{
list_del_init(&inode->i_devices);
inode->i_bdev = NULL;
inode->i_mapping = &inode->i_data;
}
static void bdev_evict_inode(struct inode *inode)
{
struct block_device *bdev = &BDEV_I(inode)->bdev;
struct list_head *p;
truncate_inode_pages(&inode->i_data, 0);
invalidate_inode_buffers(inode); /* is it needed here? */
end_writeback(inode);
spin_lock(&bdev_lock);
while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
__bd_forget(list_entry(p, struct inode, i_devices));
}
list_del_init(&bdev->bd_list);
spin_unlock(&bdev_lock);
}
static const struct super_operations bdev_sops = {
.statfs = simple_statfs,
.alloc_inode = bdev_alloc_inode,
.destroy_inode = bdev_destroy_inode,
.drop_inode = generic_delete_inode,
.evict_inode = bdev_evict_inode,
};
static struct dentry *bd_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_pseudo(fs_type, "bdev:", &bdev_sops, 0x62646576);
}
static struct file_system_type bd_type = {
.name = "bdev",
.mount = bd_mount,
.kill_sb = kill_anon_super,
};
struct super_block *blockdev_superblock __read_mostly;
void __init bdev_cache_init(void)
{
int err;
struct vfsmount *bd_mnt;
bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD|SLAB_PANIC),
init_once);
err = register_filesystem(&bd_type);
if (err)
panic("Cannot register bdev pseudo-fs");
bd_mnt = kern_mount(&bd_type);
if (IS_ERR(bd_mnt))
panic("Cannot create bdev pseudo-fs");
/*
* This vfsmount structure is only used to obtain the
* blockdev_superblock, so tell kmemleak not to report it.
*/
kmemleak_not_leak(bd_mnt);
blockdev_superblock = bd_mnt->mnt_sb; /* For writeback */
}
/*
* Most likely _very_ bad one - but then it's hardly critical for small
* /dev and can be fixed when somebody will need really large one.
* Keep in mind that it will be fed through icache hash function too.
*/
static inline unsigned long hash(dev_t dev)
{
return MAJOR(dev)+MINOR(dev);
}
static int bdev_test(struct inode *inode, void *data)
{
return BDEV_I(inode)->bdev.bd_dev == *(dev_t *)data;
}
static int bdev_set(struct inode *inode, void *data)
{
BDEV_I(inode)->bdev.bd_dev = *(dev_t *)data;
return 0;
}
static LIST_HEAD(all_bdevs);
struct block_device *bdget(dev_t dev)
{
struct block_device *bdev;
struct inode *inode;
inode = iget5_locked(blockdev_superblock, hash(dev),
bdev_test, bdev_set, &dev);
if (!inode)
return NULL;
bdev = &BDEV_I(inode)->bdev;
if (inode->i_state & I_NEW) {
bdev->bd_contains = NULL;
bdev->bd_inode = inode;
bdev->bd_block_size = (1 << inode->i_blkbits);
bdev->bd_part_count = 0;
bdev->bd_invalidated = 0;
inode->i_mode = S_IFBLK;
inode->i_rdev = dev;
inode->i_bdev = bdev;
inode->i_data.a_ops = &def_blk_aops;
mapping_set_gfp_mask(&inode->i_data, GFP_USER);
inode->i_data.backing_dev_info = &default_backing_dev_info;
spin_lock(&bdev_lock);
list_add(&bdev->bd_list, &all_bdevs);
spin_unlock(&bdev_lock);
unlock_new_inode(inode);
}
return bdev;
}
EXPORT_SYMBOL(bdget);
/**
* bdgrab -- Grab a reference to an already referenced block device
* @bdev: Block device to grab a reference to.
*/
struct block_device *bdgrab(struct block_device *bdev)
{
ihold(bdev->bd_inode);
return bdev;
}
long nr_blockdev_pages(void)
{
struct block_device *bdev;
long ret = 0;
spin_lock(&bdev_lock);
list_for_each_entry(bdev, &all_bdevs, bd_list) {
ret += bdev->bd_inode->i_mapping->nrpages;
}
spin_unlock(&bdev_lock);
return ret;
}
void bdput(struct block_device *bdev)
{
iput(bdev->bd_inode);
}
EXPORT_SYMBOL(bdput);
static struct block_device *bd_acquire(struct inode *inode)
{
struct block_device *bdev;
spin_lock(&bdev_lock);
bdev = inode->i_bdev;
if (bdev) {
ihold(bdev->bd_inode);
spin_unlock(&bdev_lock);
return bdev;
}
spin_unlock(&bdev_lock);
bdev = bdget(inode->i_rdev);
if (bdev) {
spin_lock(&bdev_lock);
if (!inode->i_bdev) {
/*
* We take an additional reference to bd_inode,
* and it's released in clear_inode() of inode.
* So, we can access it via ->i_mapping always
* without igrab().
*/
ihold(bdev->bd_inode);
inode->i_bdev = bdev;
inode->i_mapping = bdev->bd_inode->i_mapping;
list_add(&inode->i_devices, &bdev->bd_inodes);
}
spin_unlock(&bdev_lock);
}
return bdev;
}
/* Call when you free inode */
void bd_forget(struct inode *inode)
{
struct block_device *bdev = NULL;
spin_lock(&bdev_lock);
if (inode->i_bdev) {
if (!sb_is_blkdev_sb(inode->i_sb))
bdev = inode->i_bdev;
__bd_forget(inode);
}
spin_unlock(&bdev_lock);
if (bdev)
iput(bdev->bd_inode);
}
/**
* bd_may_claim - test whether a block device can be claimed
* @bdev: block device of interest
* @whole: whole block device containing @bdev, may equal @bdev
* @holder: holder trying to claim @bdev
*
* Test whther @bdev can be claimed by @holder.
*
* CONTEXT:
* spin_lock(&bdev_lock).
*
* RETURNS:
* %true if @bdev can be claimed, %false otherwise.
*/
static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
void *holder)
{
if (bdev->bd_holder == holder)
return true; /* already a holder */
else if (bdev->bd_holder != NULL)
return false; /* held by someone else */
else if (bdev->bd_contains == bdev)
return true; /* is a whole device which isn't held */
else if (whole->bd_holder == bd_claim)
return true; /* is a partition of a device that is being partitioned */
else if (whole->bd_holder != NULL)
return false; /* is a partition of a held device */
else
return true; /* is a partition of an un-held device */
}
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
/**
* bd_prepare_to_claim - prepare to claim a block device
* @bdev: block device of interest
* @whole: the whole device containing @bdev, may equal @bdev
* @holder: holder trying to claim @bdev
*
* Prepare to claim @bdev. This function fails if @bdev is already
* claimed by another holder and waits if another claiming is in
* progress. This function doesn't actually claim. On successful
* return, the caller has ownership of bd_claiming and bd_holder[s].
*
* CONTEXT:
* spin_lock(&bdev_lock). Might release bdev_lock, sleep and regrab
* it multiple times.
*
* RETURNS:
* 0 if @bdev can be claimed, -EBUSY otherwise.
*/
static int bd_prepare_to_claim(struct block_device *bdev,
struct block_device *whole, void *holder)
{
retry:
/* if someone else claimed, fail */
if (!bd_may_claim(bdev, whole, holder))
return -EBUSY;
/* if claiming is already in progress, wait for it to finish */
if (whole->bd_claiming) {
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
wait_queue_head_t *wq = bit_waitqueue(&whole->bd_claiming, 0);
DEFINE_WAIT(wait);
prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
spin_unlock(&bdev_lock);
schedule();
finish_wait(wq, &wait);
spin_lock(&bdev_lock);
goto retry;
}
/* yay, all mine */
return 0;
}
/**
* bd_start_claiming - start claiming a block device
* @bdev: block device of interest
* @holder: holder trying to claim @bdev
*
* @bdev is about to be opened exclusively. Check @bdev can be opened
* exclusively and mark that an exclusive open is in progress. Each
* successful call to this function must be matched with a call to
* either bd_finish_claiming() or bd_abort_claiming() (which do not
* fail).
*
* This function is used to gain exclusive access to the block device
* without actually causing other exclusive open attempts to fail. It
* should be used when the open sequence itself requires exclusive
* access but may subsequently fail.
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
*
* CONTEXT:
* Might sleep.
*
* RETURNS:
* Pointer to the block device containing @bdev on success, ERR_PTR()
* value on failure.
*/
static struct block_device *bd_start_claiming(struct block_device *bdev,
void *holder)
{
struct gendisk *disk;
struct block_device *whole;
int partno, err;
might_sleep();
/*
* @bdev might not have been initialized properly yet, look up
* and grab the outer block device the hard way.
*/
disk = get_gendisk(bdev->bd_dev, &partno);
if (!disk)
return ERR_PTR(-ENXIO);
whole = bdget_disk(disk, 0);
module_put(disk->fops->owner);
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
put_disk(disk);
if (!whole)
return ERR_PTR(-ENOMEM);
/* prepare to claim, if successful, mark claiming in progress */
spin_lock(&bdev_lock);
err = bd_prepare_to_claim(bdev, whole, holder);
if (err == 0) {
whole->bd_claiming = holder;
spin_unlock(&bdev_lock);
return whole;
} else {
spin_unlock(&bdev_lock);
bdput(whole);
return ERR_PTR(err);
}
}
/* releases bdev_lock */
static void __bd_abort_claiming(struct block_device *whole, void *holder)
{
BUG_ON(whole->bd_claiming != holder);
whole->bd_claiming = NULL;
wake_up_bit(&whole->bd_claiming, 0);
spin_unlock(&bdev_lock);
bdput(whole);
}
/**
* bd_abort_claiming - abort claiming a block device
* @whole: whole block device returned by bd_start_claiming()
* @holder: holder trying to claim @bdev
*
* Abort a claiming block started by bd_start_claiming(). Note that
* @whole is not the block device to be claimed but the whole device
* returned by bd_start_claiming().
*
* CONTEXT:
* Grabs and releases bdev_lock.
*/
static void bd_abort_claiming(struct block_device *whole, void *holder)
{
spin_lock(&bdev_lock);
__bd_abort_claiming(whole, holder); /* releases bdev_lock */
}
/* increment holders when we have a legitimate claim. requires bdev_lock */
static void __bd_claim(struct block_device *bdev, struct block_device *whole,
void *holder)
{
/* note that for a whole device bd_holders
* will be incremented twice, and bd_holder will
* be set to bd_claim before being set to holder
*/
whole->bd_holders++;
whole->bd_holder = bd_claim;
bdev->bd_holders++;
bdev->bd_holder = holder;
}
/**
* bd_finish_claiming - finish claiming a block device
* @bdev: block device of interest (passed to bd_start_claiming())
* @whole: whole block device returned by bd_start_claiming()
* @holder: holder trying to claim @bdev
*
* Finish a claiming block started by bd_start_claiming().
*
* CONTEXT:
* Grabs and releases bdev_lock.
*/
static void bd_finish_claiming(struct block_device *bdev,
struct block_device *whole, void *holder)
{
spin_lock(&bdev_lock);
BUG_ON(!bd_may_claim(bdev, whole, holder));
__bd_claim(bdev, whole, holder);
__bd_abort_claiming(whole, holder); /* not actually an abort */
}
/**
* bd_claim - claim a block device
* @bdev: block device to claim
* @holder: holder trying to claim @bdev
*
* Try to claim @bdev which must have been opened successfully.
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
*
* CONTEXT:
* Might sleep.
*
* RETURNS:
* 0 if successful, -EBUSY if @bdev is already claimed.
*/
int bd_claim(struct block_device *bdev, void *holder)
{
struct block_device *whole = bdev->bd_contains;
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
int res;
might_sleep();
spin_lock(&bdev_lock);
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
res = bd_prepare_to_claim(bdev, whole, holder);
if (res == 0)
__bd_claim(bdev, whole, holder);
spin_unlock(&bdev_lock);
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
return res;
}
EXPORT_SYMBOL(bd_claim);
void bd_release(struct block_device *bdev)
{
spin_lock(&bdev_lock);
if (!--bdev->bd_contains->bd_holders)
bdev->bd_contains->bd_holder = NULL;
if (!--bdev->bd_holders)
bdev->bd_holder = NULL;
spin_unlock(&bdev_lock);
}
EXPORT_SYMBOL(bd_release);
#ifdef CONFIG_SYSFS
/*
* Functions for bd_claim_by_kobject / bd_release_from_kobject
*
* If a kobject is passed to bd_claim_by_kobject()
* and the kobject has a parent directory,
* following symlinks are created:
* o from the kobject to the claimed bdev
* o from "holders" directory of the bdev to the parent of the kobject
* bd_release_from_kobject() removes these symlinks.
*
* Example:
* If /dev/dm-0 maps to /dev/sda, kobject corresponding to
* /sys/block/dm-0/slaves is passed to bd_claim_by_kobject(), then:
* /sys/block/dm-0/slaves/sda --> /sys/block/sda
* /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
*/
[PATCH] blockdev.c: check driver layer errors Check driver layer errors. Fix from: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com> In blockdevc-check-errors.patch, add_bd_holder() is modified to return error values when some of its operation failed. Among them, it returns -EEXIST when a given bd_holder object already exists in the list. However, in this case, the function completed its work successfully and need no action by its caller other than freeing unused bd_holder object. So I think it's better to return success after freeing by itself. Otherwise, bd_claim-ing with same claim pointer will fail. Typically, lvresize will fails with following message: device-mapper: reload ioctl failed: Invalid argument and you'll see messages like below in kernel log: device-mapper: table: 254:13: linear: dm-linear: Device lookup failed device-mapper: ioctl: error adding target to table Similarly, it should not add bd_holder to the list if either one of symlinking fails. I don't have a test case for this to happen but it should cause dereference of freed pointer. If a matching bd_holder is found in bd_holder_list, add_bd_holder() completes its job by just incrementing the reference count. In this case, it should be considered as success but it used to return 'fail' to let the caller free temporary bd_holder. Fixed it to return success and free given object by itself. Also, if either one of symlinking fails, the bd_holder should not be added to the list so that it can be discarded later. Otherwise, the caller will free bd_holder which is in the list. Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Cc: "Randy.Dunlap" <rdunlap@xenotime.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-29 08:58:56 +00:00
static int add_symlink(struct kobject *from, struct kobject *to)
{
if (!from || !to)
[PATCH] blockdev.c: check driver layer errors Check driver layer errors. Fix from: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com> In blockdevc-check-errors.patch, add_bd_holder() is modified to return error values when some of its operation failed. Among them, it returns -EEXIST when a given bd_holder object already exists in the list. However, in this case, the function completed its work successfully and need no action by its caller other than freeing unused bd_holder object. So I think it's better to return success after freeing by itself. Otherwise, bd_claim-ing with same claim pointer will fail. Typically, lvresize will fails with following message: device-mapper: reload ioctl failed: Invalid argument and you'll see messages like below in kernel log: device-mapper: table: 254:13: linear: dm-linear: Device lookup failed device-mapper: ioctl: error adding target to table Similarly, it should not add bd_holder to the list if either one of symlinking fails. I don't have a test case for this to happen but it should cause dereference of freed pointer. If a matching bd_holder is found in bd_holder_list, add_bd_holder() completes its job by just incrementing the reference count. In this case, it should be considered as success but it used to return 'fail' to let the caller free temporary bd_holder. Fixed it to return success and free given object by itself. Also, if either one of symlinking fails, the bd_holder should not be added to the list so that it can be discarded later. Otherwise, the caller will free bd_holder which is in the list. Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Cc: "Randy.Dunlap" <rdunlap@xenotime.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-29 08:58:56 +00:00
return 0;
return sysfs_create_link(from, to, kobject_name(to));
}
static void del_symlink(struct kobject *from, struct kobject *to)
{
if (!from || !to)
return;
sysfs_remove_link(from, kobject_name(to));
}
/*
* 'struct bd_holder' contains pointers to kobjects symlinked by
* bd_claim_by_kobject.
* It's connected to bd_holder_list which is protected by bdev->bd_sem.
*/
struct bd_holder {
struct list_head list; /* chain of holders of the bdev */
int count; /* references from the holder */
struct kobject *sdir; /* holder object, e.g. "/block/dm-0/slaves" */
struct kobject *hdev; /* e.g. "/block/dm-0" */
struct kobject *hdir; /* e.g. "/block/sda/holders" */
struct kobject *sdev; /* e.g. "/block/sda" */
};
/*
* Get references of related kobjects at once.
* Returns 1 on success. 0 on failure.
*
* Should call bd_holder_release_dirs() after successful use.
*/
static int bd_holder_grab_dirs(struct block_device *bdev,
struct bd_holder *bo)
{
if (!bdev || !bo)
return 0;
bo->sdir = kobject_get(bo->sdir);
if (!bo->sdir)
return 0;
bo->hdev = kobject_get(bo->sdir->parent);
if (!bo->hdev)
goto fail_put_sdir;
bo->sdev = kobject_get(&part_to_dev(bdev->bd_part)->kobj);
if (!bo->sdev)
goto fail_put_hdev;
bo->hdir = kobject_get(bdev->bd_part->holder_dir);
if (!bo->hdir)
goto fail_put_sdev;
return 1;
fail_put_sdev:
kobject_put(bo->sdev);
fail_put_hdev:
kobject_put(bo->hdev);
fail_put_sdir:
kobject_put(bo->sdir);
return 0;
}
/* Put references of related kobjects at once. */
static void bd_holder_release_dirs(struct bd_holder *bo)
{
kobject_put(bo->hdir);
kobject_put(bo->sdev);
kobject_put(bo->hdev);
kobject_put(bo->sdir);
}
static struct bd_holder *alloc_bd_holder(struct kobject *kobj)
{
struct bd_holder *bo;
bo = kzalloc(sizeof(*bo), GFP_KERNEL);
if (!bo)
return NULL;
bo->count = 1;
bo->sdir = kobj;
return bo;
}
static void free_bd_holder(struct bd_holder *bo)
{
kfree(bo);
}
/**
* find_bd_holder - find matching struct bd_holder from the block device
*
* @bdev: struct block device to be searched
* @bo: target struct bd_holder
*
* Returns matching entry with @bo in @bdev->bd_holder_list.
* If found, increment the reference count and return the pointer.
* If not found, returns NULL.
*/
static struct bd_holder *find_bd_holder(struct block_device *bdev,
struct bd_holder *bo)
{
struct bd_holder *tmp;
list_for_each_entry(tmp, &bdev->bd_holder_list, list)
if (tmp->sdir == bo->sdir) {
tmp->count++;
return tmp;
}
return NULL;
}
/**
* add_bd_holder - create sysfs symlinks for bd_claim() relationship
*
* @bdev: block device to be bd_claimed
* @bo: preallocated and initialized by alloc_bd_holder()
*
* Add @bo to @bdev->bd_holder_list, create symlinks.
*
* Returns 0 if symlinks are created.
* Returns -ve if something fails.
*/
static int add_bd_holder(struct block_device *bdev, struct bd_holder *bo)
{
int err;
if (!bo)
[PATCH] blockdev.c: check driver layer errors Check driver layer errors. Fix from: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com> In blockdevc-check-errors.patch, add_bd_holder() is modified to return error values when some of its operation failed. Among them, it returns -EEXIST when a given bd_holder object already exists in the list. However, in this case, the function completed its work successfully and need no action by its caller other than freeing unused bd_holder object. So I think it's better to return success after freeing by itself. Otherwise, bd_claim-ing with same claim pointer will fail. Typically, lvresize will fails with following message: device-mapper: reload ioctl failed: Invalid argument and you'll see messages like below in kernel log: device-mapper: table: 254:13: linear: dm-linear: Device lookup failed device-mapper: ioctl: error adding target to table Similarly, it should not add bd_holder to the list if either one of symlinking fails. I don't have a test case for this to happen but it should cause dereference of freed pointer. If a matching bd_holder is found in bd_holder_list, add_bd_holder() completes its job by just incrementing the reference count. In this case, it should be considered as success but it used to return 'fail' to let the caller free temporary bd_holder. Fixed it to return success and free given object by itself. Also, if either one of symlinking fails, the bd_holder should not be added to the list so that it can be discarded later. Otherwise, the caller will free bd_holder which is in the list. Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Cc: "Randy.Dunlap" <rdunlap@xenotime.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-29 08:58:56 +00:00
return -EINVAL;
if (!bd_holder_grab_dirs(bdev, bo))
[PATCH] blockdev.c: check driver layer errors Check driver layer errors. Fix from: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com> In blockdevc-check-errors.patch, add_bd_holder() is modified to return error values when some of its operation failed. Among them, it returns -EEXIST when a given bd_holder object already exists in the list. However, in this case, the function completed its work successfully and need no action by its caller other than freeing unused bd_holder object. So I think it's better to return success after freeing by itself. Otherwise, bd_claim-ing with same claim pointer will fail. Typically, lvresize will fails with following message: device-mapper: reload ioctl failed: Invalid argument and you'll see messages like below in kernel log: device-mapper: table: 254:13: linear: dm-linear: Device lookup failed device-mapper: ioctl: error adding target to table Similarly, it should not add bd_holder to the list if either one of symlinking fails. I don't have a test case for this to happen but it should cause dereference of freed pointer. If a matching bd_holder is found in bd_holder_list, add_bd_holder() completes its job by just incrementing the reference count. In this case, it should be considered as success but it used to return 'fail' to let the caller free temporary bd_holder. Fixed it to return success and free given object by itself. Also, if either one of symlinking fails, the bd_holder should not be added to the list so that it can be discarded later. Otherwise, the caller will free bd_holder which is in the list. Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Cc: "Randy.Dunlap" <rdunlap@xenotime.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-29 08:58:56 +00:00
return -EBUSY;
err = add_symlink(bo->sdir, bo->sdev);
if (err)
return err;
err = add_symlink(bo->hdir, bo->hdev);
if (err) {
del_symlink(bo->sdir, bo->sdev);
return err;
[PATCH] blockdev.c: check driver layer errors Check driver layer errors. Fix from: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com> In blockdevc-check-errors.patch, add_bd_holder() is modified to return error values when some of its operation failed. Among them, it returns -EEXIST when a given bd_holder object already exists in the list. However, in this case, the function completed its work successfully and need no action by its caller other than freeing unused bd_holder object. So I think it's better to return success after freeing by itself. Otherwise, bd_claim-ing with same claim pointer will fail. Typically, lvresize will fails with following message: device-mapper: reload ioctl failed: Invalid argument and you'll see messages like below in kernel log: device-mapper: table: 254:13: linear: dm-linear: Device lookup failed device-mapper: ioctl: error adding target to table Similarly, it should not add bd_holder to the list if either one of symlinking fails. I don't have a test case for this to happen but it should cause dereference of freed pointer. If a matching bd_holder is found in bd_holder_list, add_bd_holder() completes its job by just incrementing the reference count. In this case, it should be considered as success but it used to return 'fail' to let the caller free temporary bd_holder. Fixed it to return success and free given object by itself. Also, if either one of symlinking fails, the bd_holder should not be added to the list so that it can be discarded later. Otherwise, the caller will free bd_holder which is in the list. Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Cc: "Randy.Dunlap" <rdunlap@xenotime.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-29 08:58:56 +00:00
}
list_add_tail(&bo->list, &bdev->bd_holder_list);
return 0;
}
/**
* del_bd_holder - delete sysfs symlinks for bd_claim() relationship
*
* @bdev: block device to be bd_claimed
* @kobj: holder's kobject
*
* If there is matching entry with @kobj in @bdev->bd_holder_list
* and no other bd_claim() from the same kobject,
* remove the struct bd_holder from the list, delete symlinks for it.
*
* Returns a pointer to the struct bd_holder when it's removed from the list
* and ready to be freed.
* Returns NULL if matching claim isn't found or there is other bd_claim()
* by the same kobject.
*/
static struct bd_holder *del_bd_holder(struct block_device *bdev,
struct kobject *kobj)
{
struct bd_holder *bo;
list_for_each_entry(bo, &bdev->bd_holder_list, list) {
if (bo->sdir == kobj) {
bo->count--;
BUG_ON(bo->count < 0);
if (!bo->count) {
list_del(&bo->list);
del_symlink(bo->sdir, bo->sdev);
del_symlink(bo->hdir, bo->hdev);
bd_holder_release_dirs(bo);
return bo;
}
break;
}
}
return NULL;
}
/**
* bd_claim_by_kobject - bd_claim() with additional kobject signature
*
* @bdev: block device to be claimed
* @holder: holder's signature
* @kobj: holder's kobject
*
* Do bd_claim() and if it succeeds, create sysfs symlinks between
* the bdev and the holder's kobject.
* Use bd_release_from_kobject() when relesing the claimed bdev.
*
* Returns 0 on success. (same as bd_claim())
* Returns errno on failure.
*/
static int bd_claim_by_kobject(struct block_device *bdev, void *holder,
struct kobject *kobj)
{
int err;
struct bd_holder *bo, *found;
if (!kobj)
return -EINVAL;
bo = alloc_bd_holder(kobj);
if (!bo)
return -ENOMEM;
mutex_lock(&bdev->bd_mutex);
err = bd_claim(bdev, holder);
if (err)
goto fail;
found = find_bd_holder(bdev, bo);
if (found)
goto fail;
err = add_bd_holder(bdev, bo);
if (err)
bd_release(bdev);
else
bo = NULL;
fail:
mutex_unlock(&bdev->bd_mutex);
free_bd_holder(bo);
return err;
}
/**
* bd_release_from_kobject - bd_release() with additional kobject signature
*
* @bdev: block device to be released
* @kobj: holder's kobject
*
* Do bd_release() and remove sysfs symlinks created by bd_claim_by_kobject().
*/
static void bd_release_from_kobject(struct block_device *bdev,
struct kobject *kobj)
{
if (!kobj)
return;
mutex_lock(&bdev->bd_mutex);
bd_release(bdev);
free_bd_holder(del_bd_holder(bdev, kobj));
mutex_unlock(&bdev->bd_mutex);
}
/**
* bd_claim_by_disk - wrapper function for bd_claim_by_kobject()
*
* @bdev: block device to be claimed
* @holder: holder's signature
* @disk: holder's gendisk
*
* Call bd_claim_by_kobject() with getting @disk->slave_dir.
*/
int bd_claim_by_disk(struct block_device *bdev, void *holder,
struct gendisk *disk)
{
return bd_claim_by_kobject(bdev, holder, kobject_get(disk->slave_dir));
}
EXPORT_SYMBOL_GPL(bd_claim_by_disk);
/**
* bd_release_from_disk - wrapper function for bd_release_from_kobject()
*
* @bdev: block device to be claimed
* @disk: holder's gendisk
*
* Call bd_release_from_kobject() and put @disk->slave_dir.
*/
void bd_release_from_disk(struct block_device *bdev, struct gendisk *disk)
{
bd_release_from_kobject(bdev, disk->slave_dir);
kobject_put(disk->slave_dir);
}
EXPORT_SYMBOL_GPL(bd_release_from_disk);
#endif
/*
* Tries to open block device by device number. Use it ONLY if you
* really do not have anything better - i.e. when you are behind a
* truly sucky interface and all you are given is a device number. _Never_
* to be used for internal purposes. If you ever need it - reconsider
* your API.
*/
struct block_device *open_by_devnum(dev_t dev, fmode_t mode)
{
struct block_device *bdev = bdget(dev);
int err = -ENOMEM;
if (bdev)
err = blkdev_get(bdev, mode);
return err ? ERR_PTR(err) : bdev;
}
EXPORT_SYMBOL(open_by_devnum);
/**
* flush_disk - invalidates all buffer-cache entries on a disk
*
* @bdev: struct block device to be flushed
*
* Invalidates all buffer-cache entries on a disk. It should be called
* when a disk has been changed -- either by a media change or online
* resize.
*/
static void flush_disk(struct block_device *bdev)
{
if (__invalidate_device(bdev)) {
char name[BDEVNAME_SIZE] = "";
if (bdev->bd_disk)
disk_name(bdev->bd_disk, 0, name);
printk(KERN_WARNING "VFS: busy inodes on changed media or "
"resized disk %s\n", name);
}
if (!bdev->bd_disk)
return;
if (disk_partitionable(bdev->bd_disk))
bdev->bd_invalidated = 1;
}
/**
* check_disk_size_change - checks for disk size change and adjusts bdev size.
* @disk: struct gendisk to check
* @bdev: struct bdev to adjust.
*
* This routine checks to see if the bdev size does not match the disk size
* and adjusts it if it differs.
*/
void check_disk_size_change(struct gendisk *disk, struct block_device *bdev)
{
loff_t disk_size, bdev_size;
disk_size = (loff_t)get_capacity(disk) << 9;
bdev_size = i_size_read(bdev->bd_inode);
if (disk_size != bdev_size) {
char name[BDEVNAME_SIZE];
disk_name(disk, 0, name);
printk(KERN_INFO
"%s: detected capacity change from %lld to %lld\n",
name, bdev_size, disk_size);
i_size_write(bdev->bd_inode, disk_size);
flush_disk(bdev);
}
}
EXPORT_SYMBOL(check_disk_size_change);
/**
* revalidate_disk - wrapper for lower-level driver's revalidate_disk call-back
* @disk: struct gendisk to be revalidated
*
* This routine is a wrapper for lower-level driver's revalidate_disk
* call-backs. It is used to do common pre and post operations needed
* for all revalidate_disk operations.
*/
int revalidate_disk(struct gendisk *disk)
{
struct block_device *bdev;
int ret = 0;
if (disk->fops->revalidate_disk)
ret = disk->fops->revalidate_disk(disk);
bdev = bdget_disk(disk, 0);
if (!bdev)
return ret;
mutex_lock(&bdev->bd_mutex);
check_disk_size_change(disk, bdev);
mutex_unlock(&bdev->bd_mutex);
bdput(bdev);
return ret;
}
EXPORT_SYMBOL(revalidate_disk);
/*
* This routine checks whether a removable media has been changed,
* and invalidates all buffer-cache-entries in that case. This
* is a relatively slow routine, so we have to try to minimize using
* it. Thus it is called only upon a 'mount' or 'open'. This
* is the best way of combining speed and utility, I think.
* People changing diskettes in the middle of an operation deserve
* to lose :-)
*/
int check_disk_change(struct block_device *bdev)
{
struct gendisk *disk = bdev->bd_disk;
const struct block_device_operations *bdops = disk->fops;
if (!bdops->media_changed)
return 0;
if (!bdops->media_changed(bdev->bd_disk))
return 0;
flush_disk(bdev);
if (bdops->revalidate_disk)
bdops->revalidate_disk(bdev->bd_disk);
return 1;
}
EXPORT_SYMBOL(check_disk_change);
void bd_set_size(struct block_device *bdev, loff_t size)
{
unsigned bsize = bdev_logical_block_size(bdev);
bdev->bd_inode->i_size = size;
while (bsize < PAGE_CACHE_SIZE) {
if (size & bsize)
break;
bsize <<= 1;
}
bdev->bd_block_size = bsize;
bdev->bd_inode->i_blkbits = blksize_bits(bsize);
}
EXPORT_SYMBOL(bd_set_size);
static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
/*
* bd_mutex locking:
*
* mutex_lock(part->bd_mutex)
* mutex_lock_nested(whole->bd_mutex, 1)
*/
static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
{
struct gendisk *disk;
int ret;
int partno;
int perm = 0;
if (mode & FMODE_READ)
perm |= MAY_READ;
if (mode & FMODE_WRITE)
perm |= MAY_WRITE;
/*
* hooks: /n/, see "layering violations".
*/
if (!for_part) {
ret = devcgroup_inode_permission(bdev->bd_inode, perm);
if (ret != 0) {
bdput(bdev);
return ret;
}
}
md: make devices disappear when they are no longer needed. Currently md devices, once created, never disappear until the module is unloaded. This is essentially because the gendisk holds a reference to the mddev, and the mddev holds a reference to the gendisk, this a circular reference. If we drop the reference from mddev to gendisk, then we need to ensure that the mddev is destroyed when the gendisk is destroyed. However it is not possible to hook into the gendisk destruction process to enable this. So we drop the reference from the gendisk to the mddev and destroy the gendisk when the mddev gets destroyed. However this has a complication. Between the call __blkdev_get->get_gendisk->kobj_lookup->md_probe and the call __blkdev_get->md_open there is no obvious way to hold a reference on the mddev any more, so unless something is done, it will disappear and gendisk will be destroyed prematurely. Also, once we decide to destroy the mddev, there will be an unlockable moment before the gendisk is unlinked (blk_unregister_region) during which a new reference to the gendisk can be created. We need to ensure that this reference can not be used. i.e. the ->open must fail. So: 1/ in md_probe we set a flag in the mddev (hold_active) which indicates that the array should be treated as active, even though there are no references, and no appearance of activity. This is cleared by md_release when the device is closed if it is no longer needed. This ensures that the gendisk will survive between md_probe and md_open. 2/ In md_open we check if the mddev we expect to open matches the gendisk that we did open. If there is a mismatch we return -ERESTARTSYS and modify __blkdev_get to retry from the top in that case. In the -ERESTARTSYS sys case we make sure to wait until the old gendisk (that we succeeded in opening) is really gone so we loop at most once. Some udev configurations will always open an md device when it first appears. If we allow an md device that was just created by an open to disappear on an immediate close, then this can race with such udev configurations and result in an infinite loop the device being opened and closed, then re-open due to the 'ADD' even from the first open, and then close and so on. So we make sure an md device, once created by an open, remains active at least until some md 'ioctl' has been made on it. This means that all normal usage of md devices will allow them to disappear promptly when not needed, but the worst that an incorrect usage will do it cause an inactive md device to be left in existence (it can easily be removed). As an array can be stopped by writing to a sysfs attribute echo clear > /sys/block/mdXXX/md/array_state we need to use scheduled work for deleting the gendisk and other kobjects. This allows us to wait for any pending gendisk deletion to complete by simply calling flush_scheduled_work(). Signed-off-by: NeilBrown <neilb@suse.de>
2009-01-08 21:31:10 +00:00
restart:
ret = -ENXIO;
disk = get_gendisk(bdev->bd_dev, &partno);
if (!disk)
goto out;
mutex_lock_nested(&bdev->bd_mutex, for_part);
if (!bdev->bd_openers) {
bdev->bd_disk = disk;
bdev->bd_contains = bdev;
if (!partno) {
struct backing_dev_info *bdi;
ret = -ENXIO;
bdev->bd_part = disk_get_part(disk, partno);
if (!bdev->bd_part)
goto out_clear;
if (disk->fops->open) {
ret = disk->fops->open(bdev, mode);
md: make devices disappear when they are no longer needed. Currently md devices, once created, never disappear until the module is unloaded. This is essentially because the gendisk holds a reference to the mddev, and the mddev holds a reference to the gendisk, this a circular reference. If we drop the reference from mddev to gendisk, then we need to ensure that the mddev is destroyed when the gendisk is destroyed. However it is not possible to hook into the gendisk destruction process to enable this. So we drop the reference from the gendisk to the mddev and destroy the gendisk when the mddev gets destroyed. However this has a complication. Between the call __blkdev_get->get_gendisk->kobj_lookup->md_probe and the call __blkdev_get->md_open there is no obvious way to hold a reference on the mddev any more, so unless something is done, it will disappear and gendisk will be destroyed prematurely. Also, once we decide to destroy the mddev, there will be an unlockable moment before the gendisk is unlinked (blk_unregister_region) during which a new reference to the gendisk can be created. We need to ensure that this reference can not be used. i.e. the ->open must fail. So: 1/ in md_probe we set a flag in the mddev (hold_active) which indicates that the array should be treated as active, even though there are no references, and no appearance of activity. This is cleared by md_release when the device is closed if it is no longer needed. This ensures that the gendisk will survive between md_probe and md_open. 2/ In md_open we check if the mddev we expect to open matches the gendisk that we did open. If there is a mismatch we return -ERESTARTSYS and modify __blkdev_get to retry from the top in that case. In the -ERESTARTSYS sys case we make sure to wait until the old gendisk (that we succeeded in opening) is really gone so we loop at most once. Some udev configurations will always open an md device when it first appears. If we allow an md device that was just created by an open to disappear on an immediate close, then this can race with such udev configurations and result in an infinite loop the device being opened and closed, then re-open due to the 'ADD' even from the first open, and then close and so on. So we make sure an md device, once created by an open, remains active at least until some md 'ioctl' has been made on it. This means that all normal usage of md devices will allow them to disappear promptly when not needed, but the worst that an incorrect usage will do it cause an inactive md device to be left in existence (it can easily be removed). As an array can be stopped by writing to a sysfs attribute echo clear > /sys/block/mdXXX/md/array_state we need to use scheduled work for deleting the gendisk and other kobjects. This allows us to wait for any pending gendisk deletion to complete by simply calling flush_scheduled_work(). Signed-off-by: NeilBrown <neilb@suse.de>
2009-01-08 21:31:10 +00:00
if (ret == -ERESTARTSYS) {
/* Lost a race with 'disk' being
* deleted, try again.
* See md.c
*/
disk_put_part(bdev->bd_part);
bdev->bd_part = NULL;
module_put(disk->fops->owner);
put_disk(disk);
bdev->bd_disk = NULL;
mutex_unlock(&bdev->bd_mutex);
goto restart;
}
if (ret)
goto out_clear;
}
if (!bdev->bd_openers) {
bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
bdi = blk_get_backing_dev_info(bdev);
if (bdi == NULL)
bdi = &default_backing_dev_info;
bdev_inode_switch_bdi(bdev->bd_inode, bdi);
}
if (bdev->bd_invalidated)
rescan_partitions(disk, bdev);
} else {
struct block_device *whole;
whole = bdget_disk(disk, 0);
ret = -ENOMEM;
if (!whole)
goto out_clear;
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
BUG_ON(for_part);
ret = __blkdev_get(whole, mode, 1);
if (ret)
goto out_clear;
bdev->bd_contains = whole;
bdev_inode_switch_bdi(bdev->bd_inode,
whole->bd_inode->i_data.backing_dev_info);
bdev->bd_part = disk_get_part(disk, partno);
if (!(disk->flags & GENHD_FL_UP) ||
!bdev->bd_part || !bdev->bd_part->nr_sects) {
ret = -ENXIO;
goto out_clear;
}
bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
}
} else {
module_put(disk->fops->owner);
put_disk(disk);
disk = NULL;
if (bdev->bd_contains == bdev) {
if (bdev->bd_disk->fops->open) {
ret = bdev->bd_disk->fops->open(bdev, mode);
if (ret)
goto out_unlock_bdev;
}
if (bdev->bd_invalidated)
rescan_partitions(bdev->bd_disk, bdev);
}
}
bdev->bd_openers++;
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
if (for_part)
bdev->bd_part_count++;
mutex_unlock(&bdev->bd_mutex);
return 0;
out_clear:
disk_put_part(bdev->bd_part);
bdev->bd_disk = NULL;
bdev->bd_part = NULL;
bdev_inode_switch_bdi(bdev->bd_inode, &default_backing_dev_info);
if (bdev != bdev->bd_contains)
__blkdev_put(bdev->bd_contains, mode, 1);
bdev->bd_contains = NULL;
out_unlock_bdev:
mutex_unlock(&bdev->bd_mutex);
out:
if (disk)
module_put(disk->fops->owner);
put_disk(disk);
bdput(bdev);
return ret;
}
int blkdev_get(struct block_device *bdev, fmode_t mode)
{
return __blkdev_get(bdev, mode, 0);
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
}
EXPORT_SYMBOL(blkdev_get);
static int blkdev_open(struct inode * inode, struct file * filp)
{
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
struct block_device *whole = NULL;
struct block_device *bdev;
int res;
/*
* Preserve backwards compatibility and allow large file access
* even if userspace doesn't ask for it explicitly. Some mkfs
* binary needs it. We might want to drop this workaround
* during an unstable branch.
*/
filp->f_flags |= O_LARGEFILE;
if (filp->f_flags & O_NDELAY)
filp->f_mode |= FMODE_NDELAY;
if (filp->f_flags & O_EXCL)
filp->f_mode |= FMODE_EXCL;
if ((filp->f_flags & O_ACCMODE) == 3)
filp->f_mode |= FMODE_WRITE_IOCTL;
bdev = bd_acquire(inode);
if (bdev == NULL)
return -ENOMEM;
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
if (filp->f_mode & FMODE_EXCL) {
whole = bd_start_claiming(bdev, filp);
if (IS_ERR(whole)) {
bdput(bdev);
return PTR_ERR(whole);
}
}
filp->f_mapping = bdev->bd_inode->i_mapping;
res = blkdev_get(bdev, filp->f_mode);
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
if (whole) {
if (res == 0)
bd_finish_claiming(bdev, whole, filp);
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
else
bd_abort_claiming(whole, filp);
}
return res;
}
static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
{
int ret = 0;
struct gendisk *disk = bdev->bd_disk;
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
struct block_device *victim = NULL;
mutex_lock_nested(&bdev->bd_mutex, for_part);
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
if (for_part)
bdev->bd_part_count--;
if (!--bdev->bd_openers) {
sync_blockdev(bdev);
kill_bdev(bdev);
}
if (bdev->bd_contains == bdev) {
if (disk->fops->release)
ret = disk->fops->release(disk, mode);
}
if (!bdev->bd_openers) {
struct module *owner = disk->fops->owner;
put_disk(disk);
module_put(owner);
disk_put_part(bdev->bd_part);
bdev->bd_part = NULL;
bdev->bd_disk = NULL;
bdev_inode_switch_bdi(bdev->bd_inode,
&default_backing_dev_info);
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
if (bdev != bdev->bd_contains)
victim = bdev->bd_contains;
bdev->bd_contains = NULL;
}
mutex_unlock(&bdev->bd_mutex);
bdput(bdev);
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
if (victim)
__blkdev_put(victim, mode, 1);
return ret;
}
int blkdev_put(struct block_device *bdev, fmode_t mode)
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
{
return __blkdev_put(bdev, mode, 0);
[PATCH] lockdep: simplify some aspects of bd_mutex nesting When we open (actually blkdev_get) a partition we need to also open (get) the whole device that holds the partition. The involves some limited recursion. This patch tries to simplify some aspects of this. As well as opening the whole device, we need to increment ->bd_part_count when a partition is opened (this is used by rescan_partitions to avoid a rescan if any partition is active, as that would be confusing). The main change this patch makes is to move the inc/dec of bd_part_count into blkdev_{get,put} for the whole rather than doing it in blkdev_{get,put} for the partition. More specifically, we introduce __blkdev_get and __blkdev_put which do exactly what blkdev_{get,put} did, only with an extra "for_part" argument (blkget_{get,put} then call the __ version with a '0' for the extra argument). If for_part is 1, then the blkdev is being get(put) because a partition is being opened(closed) for the first(last) time, and so bd_part_count should be updated (on success). The particular advantage of pushing this function down is that the bd_mutex lock (which is needed to update bd_part_count) is already held at the lower level. Note that this slightly changes the semantics of bd_part_count. Instead of updating it whenever a partition is opened or released, it is now only updated on the first open or last release. This is an adequate semantic as it is only ever tested for "== 0". Having introduced these functions we remove the current bd_part_count updates from do_open (which is really the body of blkdev_get) and call __blkdev_get(... 1). Similarly in blkget_put we remove the old bd_part_count updates and call __blkget_put(..., 1). This call is moved to the end of __blkdev_put to avoid nested locks of bd_mutex. Finally the mutex_lock on whole->bd_mutex in do_open can be removed. It was only really needed to protect bd_part_count, and that is now managed (and protected) within the recursive call. The observation that bd_part_count is central to the locking issues, and the modifications to create __blkdev_put are from Peter Zijlstra. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 10:36:16 +00:00
}
EXPORT_SYMBOL(blkdev_put);
static int blkdev_close(struct inode * inode, struct file * filp)
{
struct block_device *bdev = I_BDEV(filp->f_mapping->host);
if (bdev->bd_holder == filp)
bd_release(bdev);
return blkdev_put(bdev, filp->f_mode);
}
static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
{
struct block_device *bdev = I_BDEV(file->f_mapping->host);
fmode_t mode = file->f_mode;
/*
* O_NDELAY can be altered using fcntl(.., F_SETFL, ..), so we have
* to updated it before every ioctl.
*/
if (file->f_flags & O_NDELAY)
mode |= FMODE_NDELAY;
else
mode &= ~FMODE_NDELAY;
return blkdev_ioctl(bdev, mode, cmd, arg);
}
/*
* Write data to the block device. Only intended for the block device itself
* and the raw driver which basically is a fake block device.
*
* Does not take i_mutex for the write and thus is not for general purpose
* use.
*/
ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
struct file *file = iocb->ki_filp;
ssize_t ret;
BUG_ON(iocb->ki_pos != pos);
ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
if (ret > 0 || ret == -EIOCBQUEUED) {
ssize_t err;
err = generic_write_sync(file, pos, ret);
if (err < 0 && ret > 0)
ret = err;
}
return ret;
}
EXPORT_SYMBOL_GPL(blkdev_aio_write);
/*
* Try to release a page associated with block device when the system
* is under memory pressure.
*/
static int blkdev_releasepage(struct page *page, gfp_t wait)
{
struct super_block *super = BDEV_I(page->mapping->host)->bdev.bd_super;
if (super && super->s_op->bdev_try_to_free_page)
return super->s_op->bdev_try_to_free_page(super, page, wait);
return try_to_free_buffers(page);
}
static const struct address_space_operations def_blk_aops = {
.readpage = blkdev_readpage,
.writepage = blkdev_writepage,
.sync_page = block_sync_page,
.write_begin = blkdev_write_begin,
.write_end = blkdev_write_end,
.writepages = generic_writepages,
.releasepage = blkdev_releasepage,
.direct_IO = blkdev_direct_IO,
};
const struct file_operations def_blk_fops = {
.open = blkdev_open,
.release = blkdev_close,
.llseek = block_llseek,
.read = do_sync_read,
.write = do_sync_write,
.aio_read = generic_file_aio_read,
.aio_write = blkdev_aio_write,
.mmap = generic_file_mmap,
.fsync = blkdev_fsync,
.unlocked_ioctl = block_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = compat_blkdev_ioctl,
#endif
.splice_read = generic_file_splice_read,
.splice_write = generic_file_splice_write,
};
int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)
{
int res;
mm_segment_t old_fs = get_fs();
set_fs(KERNEL_DS);
res = blkdev_ioctl(bdev, 0, cmd, arg);
set_fs(old_fs);
return res;
}
EXPORT_SYMBOL(ioctl_by_bdev);
/**
* lookup_bdev - lookup a struct block_device by name
* @pathname: special file representing the block device
*
* Get a reference to the blockdevice at @pathname in the current
* namespace if possible and return it. Return ERR_PTR(error)
* otherwise.
*/
struct block_device *lookup_bdev(const char *pathname)
{
struct block_device *bdev;
struct inode *inode;
struct path path;
int error;
if (!pathname || !*pathname)
return ERR_PTR(-EINVAL);
error = kern_path(pathname, LOOKUP_FOLLOW, &path);
if (error)
return ERR_PTR(error);
inode = path.dentry->d_inode;
error = -ENOTBLK;
if (!S_ISBLK(inode->i_mode))
goto fail;
error = -EACCES;
if (path.mnt->mnt_flags & MNT_NODEV)
goto fail;
error = -ENOMEM;
bdev = bd_acquire(inode);
if (!bdev)
goto fail;
out:
path_put(&path);
return bdev;
fail:
bdev = ERR_PTR(error);
goto out;
}
EXPORT_SYMBOL(lookup_bdev);
/**
* open_bdev_exclusive - open a block device by name and set it up for use
*
* @path: special file representing the block device
* @mode: FMODE_... combination to pass be used
* @holder: owner for exclusion
*
* Open the blockdevice described by the special file at @path, claim it
* for the @holder.
*/
struct block_device *open_bdev_exclusive(const char *path, fmode_t mode, void *holder)
{
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
struct block_device *bdev, *whole;
int error;
bdev = lookup_bdev(path);
if (IS_ERR(bdev))
return bdev;
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
whole = bd_start_claiming(bdev, holder);
if (IS_ERR(whole)) {
bdput(bdev);
return whole;
}
error = blkdev_get(bdev, mode);
if (error)
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
goto out_abort_claiming;
error = -EACCES;
if ((mode & FMODE_WRITE) && bdev_read_only(bdev))
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
goto out_blkdev_put;
bd_finish_claiming(bdev, whole, holder);
return bdev;
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
out_blkdev_put:
blkdev_put(bdev, mode);
block: implement bd_claiming and claiming block Currently, device claiming for exclusive open is done after low level open - disk->fops->open() - has completed successfully. This means that exclusive open attempts while a device is already exclusively open will fail only after disk->fops->open() is called. cdrom driver issues commands during open() which means that O_EXCL open attempt can unintentionally inject commands to in-progress command stream for burning thus disturbing burning process. In most cases, this doesn't cause problems because the first command to be issued is TUR which most devices can process in the middle of burning. However, depending on how a device replies to TUR during burning, cdrom driver may end up issuing further commands. This can't be resolved trivially by moving bd_claim() before doing actual open() because that means an open attempt which will end up failing could interfere other legit O_EXCL open attempts. ie. unconfirmed open attempts can fail others. This patch resolves the problem by introducing claiming block which is started by bd_start_claiming() and terminated either by bd_claim() or bd_abort_claiming(). bd_claim() from inside a claiming block is guaranteed to succeed and once a claiming block is started, other bd_start_claiming() or bd_claim() attempts block till the current claiming block is terminated. bd_claim() can still be used standalone although now it always synchronizes against claiming blocks, so the existing users will keep working without any change. blkdev_open() and open_bdev_exclusive() are converted to use claiming blocks so that exclusive open attempts from these functions don't interfere with the existing exclusive open. This problem was discovered while investigating bko#15403. https://bugzilla.kernel.org/show_bug.cgi?id=15403 The burning problem itself can be resolved by updating userspace probing tools to always open w/ O_EXCL. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Matthias-Christian Ott <ott@mirix.org> Cc: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-07 09:53:59 +00:00
out_abort_claiming:
bd_abort_claiming(whole, holder);
return ERR_PTR(error);
}
EXPORT_SYMBOL(open_bdev_exclusive);
/**
* close_bdev_exclusive - close a blockdevice opened by open_bdev_exclusive()
*
* @bdev: blockdevice to close
* @mode: mode, must match that used to open.
*
* This is the counterpart to open_bdev_exclusive().
*/
void close_bdev_exclusive(struct block_device *bdev, fmode_t mode)
{
bd_release(bdev);
blkdev_put(bdev, mode);
}
EXPORT_SYMBOL(close_bdev_exclusive);
int __invalidate_device(struct block_device *bdev)
{
struct super_block *sb = get_super(bdev);
int res = 0;
if (sb) {
/*
* no need to lock the super, get_super holds the
* read mutex so the filesystem cannot go away
* under us (->put_super runs with the write lock
* hold).
*/
shrink_dcache_sb(sb);
res = invalidate_inodes(sb);
drop_super(sb);
}
invalidate_bdev(bdev);
return res;
}
EXPORT_SYMBOL(__invalidate_device);