linux/fs/dlm/plock.c
Miklos Szeredi bde74e4bc6 locks: add special return value for asynchronous locks
Use a special error value FILE_LOCK_DEFERRED to mean that a locking
operation returned asynchronously.  This is returned by

  posix_lock_file() for sleeping locks to mean that the lock has been
  queued on the block list, and will be woken up when it might become
  available and needs to be retried (either fl_lmops->fl_notify() is
  called or fl_wait is woken up).

  f_op->lock() to mean either the above, or that the filesystem will
  call back with fl_lmops->fl_grant() when the result of the locking
  operation is known.  The filesystem can do this for sleeping as well
  as non-sleeping locks.

This is to make sure, that return values of -EAGAIN and -EINPROGRESS by
filesystems are not mistaken to mean an asynchronous locking.

This also makes error handling in fs/locks.c and lockd/svclock.c slightly
cleaner.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: David Teigland <teigland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-25 10:53:47 -07:00

439 lines
9.7 KiB
C

/*
* Copyright (C) 2005-2008 Red Hat, Inc. All rights reserved.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU General Public License version 2.
*/
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/poll.h>
#include <linux/dlm.h>
#include <linux/dlm_plock.h>
#include "dlm_internal.h"
#include "lockspace.h"
static spinlock_t ops_lock;
static struct list_head send_list;
static struct list_head recv_list;
static wait_queue_head_t send_wq;
static wait_queue_head_t recv_wq;
struct plock_op {
struct list_head list;
int done;
struct dlm_plock_info info;
};
struct plock_xop {
struct plock_op xop;
void *callback;
void *fl;
void *file;
struct file_lock flc;
};
static inline void set_version(struct dlm_plock_info *info)
{
info->version[0] = DLM_PLOCK_VERSION_MAJOR;
info->version[1] = DLM_PLOCK_VERSION_MINOR;
info->version[2] = DLM_PLOCK_VERSION_PATCH;
}
static int check_version(struct dlm_plock_info *info)
{
if ((DLM_PLOCK_VERSION_MAJOR != info->version[0]) ||
(DLM_PLOCK_VERSION_MINOR < info->version[1])) {
log_print("plock device version mismatch: "
"kernel (%u.%u.%u), user (%u.%u.%u)",
DLM_PLOCK_VERSION_MAJOR,
DLM_PLOCK_VERSION_MINOR,
DLM_PLOCK_VERSION_PATCH,
info->version[0],
info->version[1],
info->version[2]);
return -EINVAL;
}
return 0;
}
static void send_op(struct plock_op *op)
{
set_version(&op->info);
INIT_LIST_HEAD(&op->list);
spin_lock(&ops_lock);
list_add_tail(&op->list, &send_list);
spin_unlock(&ops_lock);
wake_up(&send_wq);
}
int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
int cmd, struct file_lock *fl)
{
struct dlm_ls *ls;
struct plock_op *op;
struct plock_xop *xop;
int rv;
ls = dlm_find_lockspace_local(lockspace);
if (!ls)
return -EINVAL;
xop = kzalloc(sizeof(*xop), GFP_KERNEL);
if (!xop) {
rv = -ENOMEM;
goto out;
}
op = &xop->xop;
op->info.optype = DLM_PLOCK_OP_LOCK;
op->info.pid = fl->fl_pid;
op->info.ex = (fl->fl_type == F_WRLCK);
op->info.wait = IS_SETLKW(cmd);
op->info.fsid = ls->ls_global_id;
op->info.number = number;
op->info.start = fl->fl_start;
op->info.end = fl->fl_end;
if (fl->fl_lmops && fl->fl_lmops->fl_grant) {
/* fl_owner is lockd which doesn't distinguish
processes on the nfs client */
op->info.owner = (__u64) fl->fl_pid;
xop->callback = fl->fl_lmops->fl_grant;
locks_init_lock(&xop->flc);
locks_copy_lock(&xop->flc, fl);
xop->fl = fl;
xop->file = file;
} else {
op->info.owner = (__u64)(long) fl->fl_owner;
xop->callback = NULL;
}
send_op(op);
if (xop->callback == NULL)
wait_event(recv_wq, (op->done != 0));
else {
rv = FILE_LOCK_DEFERRED;
goto out;
}
spin_lock(&ops_lock);
if (!list_empty(&op->list)) {
log_error(ls, "dlm_posix_lock: op on list %llx",
(unsigned long long)number);
list_del(&op->list);
}
spin_unlock(&ops_lock);
rv = op->info.rv;
if (!rv) {
if (posix_lock_file_wait(file, fl) < 0)
log_error(ls, "dlm_posix_lock: vfs lock error %llx",
(unsigned long long)number);
}
kfree(xop);
out:
dlm_put_lockspace(ls);
return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_lock);
/* Returns failure iff a succesful lock operation should be canceled */
static int dlm_plock_callback(struct plock_op *op)
{
struct file *file;
struct file_lock *fl;
struct file_lock *flc;
int (*notify)(void *, void *, int) = NULL;
struct plock_xop *xop = (struct plock_xop *)op;
int rv = 0;
spin_lock(&ops_lock);
if (!list_empty(&op->list)) {
log_print("dlm_plock_callback: op on list %llx",
(unsigned long long)op->info.number);
list_del(&op->list);
}
spin_unlock(&ops_lock);
/* check if the following 2 are still valid or make a copy */
file = xop->file;
flc = &xop->flc;
fl = xop->fl;
notify = xop->callback;
if (op->info.rv) {
notify(flc, NULL, op->info.rv);
goto out;
}
/* got fs lock; bookkeep locally as well: */
flc->fl_flags &= ~FL_SLEEP;
if (posix_lock_file(file, flc, NULL)) {
/*
* This can only happen in the case of kmalloc() failure.
* The filesystem's own lock is the authoritative lock,
* so a failure to get the lock locally is not a disaster.
* As long as the fs cannot reliably cancel locks (especially
* in a low-memory situation), we're better off ignoring
* this failure than trying to recover.
*/
log_print("dlm_plock_callback: vfs lock error %llx file %p fl %p",
(unsigned long long)op->info.number, file, fl);
}
rv = notify(flc, NULL, 0);
if (rv) {
/* XXX: We need to cancel the fs lock here: */
log_print("dlm_plock_callback: lock granted after lock request "
"failed; dangling lock!\n");
goto out;
}
out:
kfree(xop);
return rv;
}
int dlm_posix_unlock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
struct file_lock *fl)
{
struct dlm_ls *ls;
struct plock_op *op;
int rv;
ls = dlm_find_lockspace_local(lockspace);
if (!ls)
return -EINVAL;
op = kzalloc(sizeof(*op), GFP_KERNEL);
if (!op) {
rv = -ENOMEM;
goto out;
}
if (posix_lock_file_wait(file, fl) < 0)
log_error(ls, "dlm_posix_unlock: vfs unlock error %llx",
(unsigned long long)number);
op->info.optype = DLM_PLOCK_OP_UNLOCK;
op->info.pid = fl->fl_pid;
op->info.fsid = ls->ls_global_id;
op->info.number = number;
op->info.start = fl->fl_start;
op->info.end = fl->fl_end;
if (fl->fl_lmops && fl->fl_lmops->fl_grant)
op->info.owner = (__u64) fl->fl_pid;
else
op->info.owner = (__u64)(long) fl->fl_owner;
send_op(op);
wait_event(recv_wq, (op->done != 0));
spin_lock(&ops_lock);
if (!list_empty(&op->list)) {
log_error(ls, "dlm_posix_unlock: op on list %llx",
(unsigned long long)number);
list_del(&op->list);
}
spin_unlock(&ops_lock);
rv = op->info.rv;
if (rv == -ENOENT)
rv = 0;
kfree(op);
out:
dlm_put_lockspace(ls);
return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_unlock);
int dlm_posix_get(dlm_lockspace_t *lockspace, u64 number, struct file *file,
struct file_lock *fl)
{
struct dlm_ls *ls;
struct plock_op *op;
int rv;
ls = dlm_find_lockspace_local(lockspace);
if (!ls)
return -EINVAL;
op = kzalloc(sizeof(*op), GFP_KERNEL);
if (!op) {
rv = -ENOMEM;
goto out;
}
op->info.optype = DLM_PLOCK_OP_GET;
op->info.pid = fl->fl_pid;
op->info.ex = (fl->fl_type == F_WRLCK);
op->info.fsid = ls->ls_global_id;
op->info.number = number;
op->info.start = fl->fl_start;
op->info.end = fl->fl_end;
if (fl->fl_lmops && fl->fl_lmops->fl_grant)
op->info.owner = (__u64) fl->fl_pid;
else
op->info.owner = (__u64)(long) fl->fl_owner;
send_op(op);
wait_event(recv_wq, (op->done != 0));
spin_lock(&ops_lock);
if (!list_empty(&op->list)) {
log_error(ls, "dlm_posix_get: op on list %llx",
(unsigned long long)number);
list_del(&op->list);
}
spin_unlock(&ops_lock);
/* info.rv from userspace is 1 for conflict, 0 for no-conflict,
-ENOENT if there are no locks on the file */
rv = op->info.rv;
fl->fl_type = F_UNLCK;
if (rv == -ENOENT)
rv = 0;
else if (rv > 0) {
fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
fl->fl_pid = op->info.pid;
fl->fl_start = op->info.start;
fl->fl_end = op->info.end;
rv = 0;
}
kfree(op);
out:
dlm_put_lockspace(ls);
return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_get);
/* a read copies out one plock request from the send list */
static ssize_t dev_read(struct file *file, char __user *u, size_t count,
loff_t *ppos)
{
struct dlm_plock_info info;
struct plock_op *op = NULL;
if (count < sizeof(info))
return -EINVAL;
spin_lock(&ops_lock);
if (!list_empty(&send_list)) {
op = list_entry(send_list.next, struct plock_op, list);
list_move(&op->list, &recv_list);
memcpy(&info, &op->info, sizeof(info));
}
spin_unlock(&ops_lock);
if (!op)
return -EAGAIN;
if (copy_to_user(u, &info, sizeof(info)))
return -EFAULT;
return sizeof(info);
}
/* a write copies in one plock result that should match a plock_op
on the recv list */
static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
loff_t *ppos)
{
struct dlm_plock_info info;
struct plock_op *op;
int found = 0;
if (count != sizeof(info))
return -EINVAL;
if (copy_from_user(&info, u, sizeof(info)))
return -EFAULT;
if (check_version(&info))
return -EINVAL;
spin_lock(&ops_lock);
list_for_each_entry(op, &recv_list, list) {
if (op->info.fsid == info.fsid && op->info.number == info.number &&
op->info.owner == info.owner) {
list_del_init(&op->list);
found = 1;
op->done = 1;
memcpy(&op->info, &info, sizeof(info));
break;
}
}
spin_unlock(&ops_lock);
if (found) {
struct plock_xop *xop;
xop = (struct plock_xop *)op;
if (xop->callback)
dlm_plock_callback(op);
else
wake_up(&recv_wq);
} else
log_print("dev_write no op %x %llx", info.fsid,
(unsigned long long)info.number);
return count;
}
static unsigned int dev_poll(struct file *file, poll_table *wait)
{
unsigned int mask = 0;
poll_wait(file, &send_wq, wait);
spin_lock(&ops_lock);
if (!list_empty(&send_list))
mask = POLLIN | POLLRDNORM;
spin_unlock(&ops_lock);
return mask;
}
static const struct file_operations dev_fops = {
.read = dev_read,
.write = dev_write,
.poll = dev_poll,
.owner = THIS_MODULE
};
static struct miscdevice plock_dev_misc = {
.minor = MISC_DYNAMIC_MINOR,
.name = DLM_PLOCK_MISC_NAME,
.fops = &dev_fops
};
int dlm_plock_init(void)
{
int rv;
spin_lock_init(&ops_lock);
INIT_LIST_HEAD(&send_list);
INIT_LIST_HEAD(&recv_list);
init_waitqueue_head(&send_wq);
init_waitqueue_head(&recv_wq);
rv = misc_register(&plock_dev_misc);
if (rv)
log_print("dlm_plock_init: misc_register failed %d", rv);
return rv;
}
void dlm_plock_exit(void)
{
if (misc_deregister(&plock_dev_misc) < 0)
log_print("dlm_plock_exit: misc_deregister failed");
}