linux/fs/fuse/dev.c

878 lines
22 KiB
C

/*
FUSE: Filesystem in Userspace
Copyright (C) 2001-2005 Miklos Szeredi <miklos@szeredi.hu>
This program can be distributed under the terms of the GNU GPL.
See the file COPYING.
*/
#include "fuse_i.h"
#include <linux/init.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/uio.h>
#include <linux/miscdevice.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/slab.h>
MODULE_ALIAS_MISCDEV(FUSE_MINOR);
static kmem_cache_t *fuse_req_cachep;
static inline struct fuse_conn *fuse_get_conn(struct file *file)
{
struct fuse_conn *fc;
spin_lock(&fuse_lock);
fc = file->private_data;
if (fc && !fc->mounted)
fc = NULL;
spin_unlock(&fuse_lock);
return fc;
}
static inline void fuse_request_init(struct fuse_req *req)
{
memset(req, 0, sizeof(*req));
INIT_LIST_HEAD(&req->list);
init_waitqueue_head(&req->waitq);
atomic_set(&req->count, 1);
}
struct fuse_req *fuse_request_alloc(void)
{
struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, SLAB_KERNEL);
if (req)
fuse_request_init(req);
return req;
}
void fuse_request_free(struct fuse_req *req)
{
kmem_cache_free(fuse_req_cachep, req);
}
static inline void block_sigs(sigset_t *oldset)
{
sigset_t mask;
siginitsetinv(&mask, sigmask(SIGKILL));
sigprocmask(SIG_BLOCK, &mask, oldset);
}
static inline void restore_sigs(sigset_t *oldset)
{
sigprocmask(SIG_SETMASK, oldset, NULL);
}
void fuse_reset_request(struct fuse_req *req)
{
int preallocated = req->preallocated;
BUG_ON(atomic_read(&req->count) != 1);
fuse_request_init(req);
req->preallocated = preallocated;
}
static void __fuse_get_request(struct fuse_req *req)
{
atomic_inc(&req->count);
}
/* Must be called with > 1 refcount */
static void __fuse_put_request(struct fuse_req *req)
{
BUG_ON(atomic_read(&req->count) < 2);
atomic_dec(&req->count);
}
static struct fuse_req *do_get_request(struct fuse_conn *fc)
{
struct fuse_req *req;
spin_lock(&fuse_lock);
BUG_ON(list_empty(&fc->unused_list));
req = list_entry(fc->unused_list.next, struct fuse_req, list);
list_del_init(&req->list);
spin_unlock(&fuse_lock);
fuse_request_init(req);
req->preallocated = 1;
req->in.h.uid = current->fsuid;
req->in.h.gid = current->fsgid;
req->in.h.pid = current->pid;
return req;
}
/* This can return NULL, but only in case it's interrupted by a SIGKILL */
struct fuse_req *fuse_get_request(struct fuse_conn *fc)
{
int intr;
sigset_t oldset;
block_sigs(&oldset);
intr = down_interruptible(&fc->outstanding_sem);
restore_sigs(&oldset);
return intr ? NULL : do_get_request(fc);
}
static void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req)
{
spin_lock(&fuse_lock);
if (req->preallocated)
list_add(&req->list, &fc->unused_list);
else
fuse_request_free(req);
/* If we are in debt decrease that first */
if (fc->outstanding_debt)
fc->outstanding_debt--;
else
up(&fc->outstanding_sem);
spin_unlock(&fuse_lock);
}
void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
if (atomic_dec_and_test(&req->count))
fuse_putback_request(fc, req);
}
void fuse_release_background(struct fuse_req *req)
{
iput(req->inode);
iput(req->inode2);
if (req->file)
fput(req->file);
spin_lock(&fuse_lock);
list_del(&req->bg_entry);
spin_unlock(&fuse_lock);
}
/*
* This function is called when a request is finished. Either a reply
* has arrived or it was interrupted (and not yet sent) or some error
* occured during communication with userspace, or the device file was
* closed. It decreases the referece count for the request. In case
* of a background request the referece to the stored objects are
* released. The requester thread is woken up (if still waiting), and
* finally the request is either freed or put on the unused_list
*
* Called with fuse_lock, unlocks it
*/
static void request_end(struct fuse_conn *fc, struct fuse_req *req)
{
int putback;
req->finished = 1;
putback = atomic_dec_and_test(&req->count);
spin_unlock(&fuse_lock);
if (req->background) {
down_read(&fc->sbput_sem);
if (fc->mounted)
fuse_release_background(req);
up_read(&fc->sbput_sem);
}
wake_up(&req->waitq);
if (req->in.h.opcode == FUSE_INIT) {
int i;
if (req->misc.init_in_out.major != FUSE_KERNEL_VERSION)
fc->conn_error = 1;
/* After INIT reply is received other requests can go
out. So do (FUSE_MAX_OUTSTANDING - 1) number of
up()s on outstanding_sem. The last up() is done in
fuse_putback_request() */
for (i = 1; i < FUSE_MAX_OUTSTANDING; i++)
up(&fc->outstanding_sem);
}
if (putback)
fuse_putback_request(fc, req);
}
/*
* Unfortunately request interruption not just solves the deadlock
* problem, it causes problems too. These stem from the fact, that an
* interrupted request is continued to be processed in userspace,
* while all the locks and object references (inode and file) held
* during the operation are released.
*
* To release the locks is exactly why there's a need to interrupt the
* request, so there's not a lot that can be done about this, except
* introduce additional locking in userspace.
*
* More important is to keep inode and file references until userspace
* has replied, otherwise FORGET and RELEASE could be sent while the
* inode/file is still used by the filesystem.
*
* For this reason the concept of "background" request is introduced.
* An interrupted request is backgrounded if it has been already sent
* to userspace. Backgrounding involves getting an extra reference to
* inode(s) or file used in the request, and adding the request to
* fc->background list. When a reply is received for a background
* request, the object references are released, and the request is
* removed from the list. If the filesystem is unmounted while there
* are still background requests, the list is walked and references
* are released as if a reply was received.
*
* There's one more use for a background request. The RELEASE message is
* always sent as background, since it doesn't return an error or
* data.
*/
static void background_request(struct fuse_conn *fc, struct fuse_req *req)
{
req->background = 1;
list_add(&req->bg_entry, &fc->background);
if (req->inode)
req->inode = igrab(req->inode);
if (req->inode2)
req->inode2 = igrab(req->inode2);
if (req->file)
get_file(req->file);
}
/* Called with fuse_lock held. Releases, and then reacquires it. */
static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
{
sigset_t oldset;
spin_unlock(&fuse_lock);
block_sigs(&oldset);
wait_event_interruptible(req->waitq, req->finished);
restore_sigs(&oldset);
spin_lock(&fuse_lock);
if (req->finished)
return;
req->out.h.error = -EINTR;
req->interrupted = 1;
if (req->locked) {
/* This is uninterruptible sleep, because data is
being copied to/from the buffers of req. During
locked state, there mustn't be any filesystem
operation (e.g. page fault), since that could lead
to deadlock */
spin_unlock(&fuse_lock);
wait_event(req->waitq, !req->locked);
spin_lock(&fuse_lock);
}
if (!req->sent && !list_empty(&req->list)) {
list_del(&req->list);
__fuse_put_request(req);
} else if (!req->finished && req->sent)
background_request(fc, req);
}
static unsigned len_args(unsigned numargs, struct fuse_arg *args)
{
unsigned nbytes = 0;
unsigned i;
for (i = 0; i < numargs; i++)
nbytes += args[i].size;
return nbytes;
}
static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
{
fc->reqctr++;
/* zero is special */
if (fc->reqctr == 0)
fc->reqctr = 1;
req->in.h.unique = fc->reqctr;
req->in.h.len = sizeof(struct fuse_in_header) +
len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
if (!req->preallocated) {
/* If request is not preallocated (either FORGET or
RELEASE), then still decrease outstanding_sem, so
user can't open infinite number of files while not
processing the RELEASE requests. However for
efficiency do it without blocking, so if down()
would block, just increase the debt instead */
if (down_trylock(&fc->outstanding_sem))
fc->outstanding_debt++;
}
list_add_tail(&req->list, &fc->pending);
wake_up(&fc->waitq);
}
/*
* This can only be interrupted by a SIGKILL
*/
void request_send(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 1;
spin_lock(&fuse_lock);
if (!fc->connected)
req->out.h.error = -ENOTCONN;
else if (fc->conn_error)
req->out.h.error = -ECONNREFUSED;
else {
queue_request(fc, req);
/* acquire extra reference, since request is still needed
after request_end() */
__fuse_get_request(req);
request_wait_answer(fc, req);
}
spin_unlock(&fuse_lock);
}
static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
{
spin_lock(&fuse_lock);
if (fc->connected) {
queue_request(fc, req);
spin_unlock(&fuse_lock);
} else {
req->out.h.error = -ENOTCONN;
request_end(fc, req);
}
}
void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 0;
request_send_nowait(fc, req);
}
void request_send_background(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 1;
spin_lock(&fuse_lock);
background_request(fc, req);
spin_unlock(&fuse_lock);
request_send_nowait(fc, req);
}
void fuse_send_init(struct fuse_conn *fc)
{
/* This is called from fuse_read_super() so there's guaranteed
to be a request available */
struct fuse_req *req = do_get_request(fc);
struct fuse_init_in_out *arg = &req->misc.init_in_out;
arg->major = FUSE_KERNEL_VERSION;
arg->minor = FUSE_KERNEL_MINOR_VERSION;
req->in.h.opcode = FUSE_INIT;
req->in.numargs = 1;
req->in.args[0].size = sizeof(*arg);
req->in.args[0].value = arg;
req->out.numargs = 1;
req->out.args[0].size = sizeof(*arg);
req->out.args[0].value = arg;
request_send_background(fc, req);
}
/*
* Lock the request. Up to the next unlock_request() there mustn't be
* anything that could cause a page-fault. If the request was already
* interrupted bail out.
*/
static inline int lock_request(struct fuse_req *req)
{
int err = 0;
if (req) {
spin_lock(&fuse_lock);
if (req->interrupted)
err = -ENOENT;
else
req->locked = 1;
spin_unlock(&fuse_lock);
}
return err;
}
/*
* Unlock request. If it was interrupted during being locked, the
* requester thread is currently waiting for it to be unlocked, so
* wake it up.
*/
static inline void unlock_request(struct fuse_req *req)
{
if (req) {
spin_lock(&fuse_lock);
req->locked = 0;
if (req->interrupted)
wake_up(&req->waitq);
spin_unlock(&fuse_lock);
}
}
struct fuse_copy_state {
int write;
struct fuse_req *req;
const struct iovec *iov;
unsigned long nr_segs;
unsigned long seglen;
unsigned long addr;
struct page *pg;
void *mapaddr;
void *buf;
unsigned len;
};
static void fuse_copy_init(struct fuse_copy_state *cs, int write,
struct fuse_req *req, const struct iovec *iov,
unsigned long nr_segs)
{
memset(cs, 0, sizeof(*cs));
cs->write = write;
cs->req = req;
cs->iov = iov;
cs->nr_segs = nr_segs;
}
/* Unmap and put previous page of userspace buffer */
static inline void fuse_copy_finish(struct fuse_copy_state *cs)
{
if (cs->mapaddr) {
kunmap_atomic(cs->mapaddr, KM_USER0);
if (cs->write) {
flush_dcache_page(cs->pg);
set_page_dirty_lock(cs->pg);
}
put_page(cs->pg);
cs->mapaddr = NULL;
}
}
/*
* Get another pagefull of userspace buffer, and map it to kernel
* address space, and lock request
*/
static int fuse_copy_fill(struct fuse_copy_state *cs)
{
unsigned long offset;
int err;
unlock_request(cs->req);
fuse_copy_finish(cs);
if (!cs->seglen) {
BUG_ON(!cs->nr_segs);
cs->seglen = cs->iov[0].iov_len;
cs->addr = (unsigned long) cs->iov[0].iov_base;
cs->iov ++;
cs->nr_segs --;
}
down_read(&current->mm->mmap_sem);
err = get_user_pages(current, current->mm, cs->addr, 1, cs->write, 0,
&cs->pg, NULL);
up_read(&current->mm->mmap_sem);
if (err < 0)
return err;
BUG_ON(err != 1);
offset = cs->addr % PAGE_SIZE;
cs->mapaddr = kmap_atomic(cs->pg, KM_USER0);
cs->buf = cs->mapaddr + offset;
cs->len = min(PAGE_SIZE - offset, cs->seglen);
cs->seglen -= cs->len;
cs->addr += cs->len;
return lock_request(cs->req);
}
/* Do as much copy to/from userspace buffer as we can */
static inline int fuse_copy_do(struct fuse_copy_state *cs, void **val,
unsigned *size)
{
unsigned ncpy = min(*size, cs->len);
if (val) {
if (cs->write)
memcpy(cs->buf, *val, ncpy);
else
memcpy(*val, cs->buf, ncpy);
*val += ncpy;
}
*size -= ncpy;
cs->len -= ncpy;
cs->buf += ncpy;
return ncpy;
}
/*
* Copy a page in the request to/from the userspace buffer. Must be
* done atomically
*/
static inline int fuse_copy_page(struct fuse_copy_state *cs, struct page *page,
unsigned offset, unsigned count, int zeroing)
{
if (page && zeroing && count < PAGE_SIZE) {
void *mapaddr = kmap_atomic(page, KM_USER1);
memset(mapaddr, 0, PAGE_SIZE);
kunmap_atomic(mapaddr, KM_USER1);
}
while (count) {
int err;
if (!cs->len && (err = fuse_copy_fill(cs)))
return err;
if (page) {
void *mapaddr = kmap_atomic(page, KM_USER1);
void *buf = mapaddr + offset;
offset += fuse_copy_do(cs, &buf, &count);
kunmap_atomic(mapaddr, KM_USER1);
} else
offset += fuse_copy_do(cs, NULL, &count);
}
if (page && !cs->write)
flush_dcache_page(page);
return 0;
}
/* Copy pages in the request to/from userspace buffer */
static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
int zeroing)
{
unsigned i;
struct fuse_req *req = cs->req;
unsigned offset = req->page_offset;
unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset);
for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) {
struct page *page = req->pages[i];
int err = fuse_copy_page(cs, page, offset, count, zeroing);
if (err)
return err;
nbytes -= count;
count = min(nbytes, (unsigned) PAGE_SIZE);
offset = 0;
}
return 0;
}
/* Copy a single argument in the request to/from userspace buffer */
static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size)
{
while (size) {
int err;
if (!cs->len && (err = fuse_copy_fill(cs)))
return err;
fuse_copy_do(cs, &val, &size);
}
return 0;
}
/* Copy request arguments to/from userspace buffer */
static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
unsigned argpages, struct fuse_arg *args,
int zeroing)
{
int err = 0;
unsigned i;
for (i = 0; !err && i < numargs; i++) {
struct fuse_arg *arg = &args[i];
if (i == numargs - 1 && argpages)
err = fuse_copy_pages(cs, arg->size, zeroing);
else
err = fuse_copy_one(cs, arg->value, arg->size);
}
return err;
}
/* Wait until a request is available on the pending list */
static void request_wait(struct fuse_conn *fc)
{
DECLARE_WAITQUEUE(wait, current);
add_wait_queue_exclusive(&fc->waitq, &wait);
while (fc->mounted && list_empty(&fc->pending)) {
set_current_state(TASK_INTERRUPTIBLE);
if (signal_pending(current))
break;
spin_unlock(&fuse_lock);
schedule();
spin_lock(&fuse_lock);
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&fc->waitq, &wait);
}
/*
* Read a single request into the userspace filesystem's buffer. This
* function waits until a request is available, then removes it from
* the pending list and copies request data to userspace buffer. If
* no reply is needed (FORGET) or request has been interrupted or
* there was an error during the copying then it's finished by calling
* request_end(). Otherwise add it to the processing list, and set
* the 'sent' flag.
*/
static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov,
unsigned long nr_segs, loff_t *off)
{
int err;
struct fuse_conn *fc;
struct fuse_req *req;
struct fuse_in *in;
struct fuse_copy_state cs;
unsigned reqsize;
spin_lock(&fuse_lock);
fc = file->private_data;
err = -EPERM;
if (!fc)
goto err_unlock;
request_wait(fc);
err = -ENODEV;
if (!fc->mounted)
goto err_unlock;
err = -ERESTARTSYS;
if (list_empty(&fc->pending))
goto err_unlock;
req = list_entry(fc->pending.next, struct fuse_req, list);
list_del_init(&req->list);
spin_unlock(&fuse_lock);
in = &req->in;
reqsize = req->in.h.len;
fuse_copy_init(&cs, 1, req, iov, nr_segs);
err = -EINVAL;
if (iov_length(iov, nr_segs) >= reqsize) {
err = fuse_copy_one(&cs, &in->h, sizeof(in->h));
if (!err)
err = fuse_copy_args(&cs, in->numargs, in->argpages,
(struct fuse_arg *) in->args, 0);
}
fuse_copy_finish(&cs);
spin_lock(&fuse_lock);
req->locked = 0;
if (!err && req->interrupted)
err = -ENOENT;
if (err) {
if (!req->interrupted)
req->out.h.error = -EIO;
request_end(fc, req);
return err;
}
if (!req->isreply)
request_end(fc, req);
else {
req->sent = 1;
list_add_tail(&req->list, &fc->processing);
spin_unlock(&fuse_lock);
}
return reqsize;
err_unlock:
spin_unlock(&fuse_lock);
return err;
}
static ssize_t fuse_dev_read(struct file *file, char __user *buf,
size_t nbytes, loff_t *off)
{
struct iovec iov;
iov.iov_len = nbytes;
iov.iov_base = buf;
return fuse_dev_readv(file, &iov, 1, off);
}
/* Look up request on processing list by unique ID */
static struct fuse_req *request_find(struct fuse_conn *fc, u64 unique)
{
struct list_head *entry;
list_for_each(entry, &fc->processing) {
struct fuse_req *req;
req = list_entry(entry, struct fuse_req, list);
if (req->in.h.unique == unique)
return req;
}
return NULL;
}
static int copy_out_args(struct fuse_copy_state *cs, struct fuse_out *out,
unsigned nbytes)
{
unsigned reqsize = sizeof(struct fuse_out_header);
if (out->h.error)
return nbytes != reqsize ? -EINVAL : 0;
reqsize += len_args(out->numargs, out->args);
if (reqsize < nbytes || (reqsize > nbytes && !out->argvar))
return -EINVAL;
else if (reqsize > nbytes) {
struct fuse_arg *lastarg = &out->args[out->numargs-1];
unsigned diffsize = reqsize - nbytes;
if (diffsize > lastarg->size)
return -EINVAL;
lastarg->size -= diffsize;
}
return fuse_copy_args(cs, out->numargs, out->argpages, out->args,
out->page_zeroing);
}
/*
* Write a single reply to a request. First the header is copied from
* the write buffer. The request is then searched on the processing
* list by the unique ID found in the header. If found, then remove
* it from the list and copy the rest of the buffer to the request.
* The request is finished by calling request_end()
*/
static ssize_t fuse_dev_writev(struct file *file, const struct iovec *iov,
unsigned long nr_segs, loff_t *off)
{
int err;
unsigned nbytes = iov_length(iov, nr_segs);
struct fuse_req *req;
struct fuse_out_header oh;
struct fuse_copy_state cs;
struct fuse_conn *fc = fuse_get_conn(file);
if (!fc)
return -ENODEV;
fuse_copy_init(&cs, 0, NULL, iov, nr_segs);
if (nbytes < sizeof(struct fuse_out_header))
return -EINVAL;
err = fuse_copy_one(&cs, &oh, sizeof(oh));
if (err)
goto err_finish;
err = -EINVAL;
if (!oh.unique || oh.error <= -1000 || oh.error > 0 ||
oh.len != nbytes)
goto err_finish;
spin_lock(&fuse_lock);
req = request_find(fc, oh.unique);
err = -EINVAL;
if (!req)
goto err_unlock;
list_del_init(&req->list);
if (req->interrupted) {
request_end(fc, req);
fuse_copy_finish(&cs);
return -ENOENT;
}
req->out.h = oh;
req->locked = 1;
cs.req = req;
spin_unlock(&fuse_lock);
err = copy_out_args(&cs, &req->out, nbytes);
fuse_copy_finish(&cs);
spin_lock(&fuse_lock);
req->locked = 0;
if (!err) {
if (req->interrupted)
err = -ENOENT;
} else if (!req->interrupted)
req->out.h.error = -EIO;
request_end(fc, req);
return err ? err : nbytes;
err_unlock:
spin_unlock(&fuse_lock);
err_finish:
fuse_copy_finish(&cs);
return err;
}
static ssize_t fuse_dev_write(struct file *file, const char __user *buf,
size_t nbytes, loff_t *off)
{
struct iovec iov;
iov.iov_len = nbytes;
iov.iov_base = (char __user *) buf;
return fuse_dev_writev(file, &iov, 1, off);
}
static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
{
struct fuse_conn *fc = fuse_get_conn(file);
unsigned mask = POLLOUT | POLLWRNORM;
if (!fc)
return -ENODEV;
poll_wait(file, &fc->waitq, wait);
spin_lock(&fuse_lock);
if (!list_empty(&fc->pending))
mask |= POLLIN | POLLRDNORM;
spin_unlock(&fuse_lock);
return mask;
}
/* Abort all requests on the given list (pending or processing) */
static void end_requests(struct fuse_conn *fc, struct list_head *head)
{
while (!list_empty(head)) {
struct fuse_req *req;
req = list_entry(head->next, struct fuse_req, list);
list_del_init(&req->list);
req->out.h.error = -ECONNABORTED;
request_end(fc, req);
spin_lock(&fuse_lock);
}
}
static int fuse_dev_release(struct inode *inode, struct file *file)
{
struct fuse_conn *fc;
spin_lock(&fuse_lock);
fc = file->private_data;
if (fc) {
fc->connected = 0;
end_requests(fc, &fc->pending);
end_requests(fc, &fc->processing);
fuse_release_conn(fc);
}
spin_unlock(&fuse_lock);
return 0;
}
struct file_operations fuse_dev_operations = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.read = fuse_dev_read,
.readv = fuse_dev_readv,
.write = fuse_dev_write,
.writev = fuse_dev_writev,
.poll = fuse_dev_poll,
.release = fuse_dev_release,
};
static struct miscdevice fuse_miscdevice = {
.minor = FUSE_MINOR,
.name = "fuse",
.fops = &fuse_dev_operations,
};
int __init fuse_dev_init(void)
{
int err = -ENOMEM;
fuse_req_cachep = kmem_cache_create("fuse_request",
sizeof(struct fuse_req),
0, 0, NULL, NULL);
if (!fuse_req_cachep)
goto out;
err = misc_register(&fuse_miscdevice);
if (err)
goto out_cache_clean;
return 0;
out_cache_clean:
kmem_cache_destroy(fuse_req_cachep);
out:
return err;
}
void fuse_dev_cleanup(void)
{
misc_deregister(&fuse_miscdevice);
kmem_cache_destroy(fuse_req_cachep);
}