- 根目录:
- fs
- afs
- flock.c
/* AFS file locking support
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include "internal.h"
#define AFS_LOCK_GRANTED 0
#define AFS_LOCK_PENDING 1
static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
static void afs_fl_release_private(struct file_lock *fl);
static struct workqueue_struct *afs_lock_manager;
static DEFINE_MUTEX(afs_lock_manager_mutex);
static const struct file_lock_operations afs_lock_ops = {
.fl_copy_lock = afs_fl_copy_lock,
.fl_release_private = afs_fl_release_private,
};
/*
* initialise the lock manager thread if it isn't already running
*/
static int afs_init_lock_manager(void)
{
int ret;
ret = 0;
if (!afs_lock_manager) {
mutex_lock(&afs_lock_manager_mutex);
if (!afs_lock_manager) {
afs_lock_manager =
create_singlethread_workqueue("kafs_lockd");
if (!afs_lock_manager)
ret = -ENOMEM;
}
mutex_unlock(&afs_lock_manager_mutex);
}
return ret;
}
/*
* destroy the lock manager thread if it's running
*/
void __exit afs_kill_lock_manager(void)
{
if (afs_lock_manager)
destroy_workqueue(afs_lock_manager);
}
/*
* if the callback is broken on this vnode, then the lock may now be available
*/
void afs_lock_may_be_available(struct afs_vnode *vnode)
{
_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
}
/*
* the lock will time out in 5 minutes unless we extend it, so schedule
* extension in a bit less than that time
*/
static void afs_schedule_lock_extension(struct afs_vnode *vnode)
{
queue_delayed_work(afs_lock_manager, &vnode->lock_work,
AFS_LOCKWAIT * HZ / 2);
}
/*
* grant one or more locks (readlocks are allowed to jump the queue if the
* first lock in the queue is itself a readlock)
* - the caller must hold the vnode lock
*/
static void afs_grant_locks(struct afs_vnode *vnode, struct file_lock *fl)
{
struct file_lock *p, *_p;
list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
if (fl->fl_type == F_RDLCK) {
list_for_each_entry_safe(p, _p, &vnode->pending_locks,
fl_u.afs.link) {
if (p->fl_type == F_RDLCK) {
p->fl_u.afs.state = AFS_LOCK_GRANTED;
list_move_tail(&p->fl_u.afs.link,
&vnode->granted_locks);
wake_up(&p->fl_wait);
}
}
}
}
/*
* do work for a lock, including:
* - probing for a lock we're waiting on but didn't get immediately
* - extending a lock that's close to timing out
*/
void afs_lock_work(struct work_struct *work)
{
struct afs_vnode *vnode =
container_of(work, struct afs_vnode, lock_work.work);
struct file_lock *fl;
afs_lock_type_t type;
struct key *key;
int ret;
_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
spin_lock(&vnode->lock);
if (test_bit(AFS_VNODE_UNLOCKING, &vnode->flags)) {
_debug("unlock");
spin_unlock(&vnode->lock);
/* attempt to release the server lock; if it fails, we just
* wait 5 minutes and it'll time out anyway */
ret = afs_vnode_release_lock(vnode, vnode->unlock_key);
if (ret < 0)
printk(KERN_WARNING "AFS:"
" Failed to release lock on {%x:%x} error %d\n",
vnode->fid.vid, vnode->fid.vnode, ret);
spin_lock(&vnode->lock);
key_put(vnode->unlock_key);
vnode->unlock_key = NULL;
clear_bit(AFS_VNODE_UNLOCKING, &vnode->flags);
}
/* if we've got a lock, then it must be time to extend that lock as AFS
* locks time out after 5 minutes */
if (!list_empty(&vnode->granted_locks)) {
_debug("extend");
if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
BUG();
fl = list_entry(vnode->granted_locks.next,
struct file_lock, fl_u.afs.link);
key = key_get(fl->fl_file->private_data);
spin_unlock(&vnode->lock);
ret = afs_vnode_extend_lock(vnode, key);
clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
key_put(key);
switch (ret) {
case 0:
afs_schedule_lock_extension(vnode);
break;
default:
/* ummm... we failed to extend the lock - retry
* extension shortly */
printk(KERN_WARNING "AFS:"
" Failed to extend lock on {%x:%x} error %d\n",
vnode->fid.vid, vnode->fid.vnode, ret);
queue_delayed_work(afs_lock_manager, &vnode->lock_work,
HZ * 10);
break;
}
_leave(" [extend]");
return;
}
/* if we don't have a granted lock, then we must've been called back by
* the server, and so if might be possible to get a lock we're
* currently waiting for */
if (!list_empty(&vnode->pending_locks)) {
_debug("get");
if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
BUG();
fl = list_entry(vnode->pending_locks.next,
struct file_lock, fl_u.afs.link);
key = key_get(fl->fl_file->private_data);
type = (fl->fl_type == F_RDLCK) ?
AFS_LOCK_READ : AFS_LOCK_WRITE;
spin_unlock(&vnode->lock);
ret = afs_vnode_set_lock(vnode, key, type);
clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
switch (ret) {
case -EWOULDBLOCK:
_debug("blocked");
break;
case 0:
_debug("acquired");
if (type == AFS_LOCK_READ)
set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
else
set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
ret = AFS_LOCK_GRANTED;
default:
spin_lock(&vnode->lock);
/* the pending lock may have been withdrawn due to a
* signal */
if (list_entry(vnode->pending_locks.next,
struct file_lock, fl_u.afs.link) == fl) {
fl->fl_u.afs.state = ret;
if (ret == AFS_LOCK_GRANTED)
afs_grant_locks(vnode, fl);
else
list_del_init(&fl->fl_u.afs.link);
wake_up(&fl->fl_wait);
spin_unlock(&vnode->lock);
} else {
_debug("withdrawn");
clear_bit(AFS_VNODE_READLOCKED, &vnode->flags);
clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
spin_unlock(&vnode->lock);
afs_vnode_release_lock(vnode, key);
if (!list_empty(&vnode->pending_locks))
afs_lock_may_be_available(vnode);
}
break;
}
key_put(key);
_leave(" [pend]");
return;
}
/* looks like the lock request was withdrawn on a signal */
spin_unlock(&vnode->lock);
_leave(" [no locks]");
}
/*
* pass responsibility for the unlocking of a vnode on the server to the
* manager thread, lest a pending signal in the calling thread interrupt
* AF_RXRPC
* - the caller must hold the vnode lock
*/
static void afs_defer_unlock(struct afs_vnode *vnode, struct key *key)
{
cancel_delayed_work(&vnode->lock_work);
if (!test_and_clear_bit(AFS_VNODE_READLOCKED, &vnode->flags) &&
!test_and_clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags))
BUG();
if (test_and_set_bit(AFS_VNODE_UNLOCKING, &vnode->flags))
BUG();
vnode->unlock_key = key_get(key);
afs_lock_may_be_available(vnode);
}
/*
* request a lock on a file on the server
*/
static int afs_do_setlk(struct file *file, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
afs_lock_type_t type;
struct key *key = file->private_data;
int ret;
_enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
/* only whole-file locks are supported */
if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
return -EINVAL;
ret = afs_init_lock_manager();
if (ret < 0)
return ret;
fl->fl_ops = &afs_lock_ops;
INIT_LIST_HEAD(&fl->fl_u.afs.link);
fl->fl_u.afs.state = AFS_LOCK_PENDING;
type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
lock_flocks();
/* make sure we've got a callback on this file and that our view of the
* data version is up to date */
ret = afs_vnode_fetch_status(vnode, NULL, key);
if (ret < 0)
goto error;
if (vnode->status.lock_count != 0 && !(fl->fl_flags & FL_SLEEP)) {
ret = -EAGAIN;
goto error;
}
spin_lock(&vnode->lock);
/* if we've already got a readlock on the server then we can instantly
* grant another readlock, irrespective of whether there are any
* pending writelocks */
if (type == AFS_LOCK_READ &&
vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
_debug("instant readlock");
ASSERTCMP(vnode->flags &
((1 << AFS_VNODE_LOCKING) |
(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
ASSERT(!list_empty(&vnode->granted_locks));
goto sharing_existing_lock;
}
/* if there's no-one else with a lock on this vnode, then we need to
* ask the server for a lock */
if (list_empty(&vnode->pending_locks) &&
list_empty(&vnode->granted_locks)) {
_debug("not locked");
ASSERTCMP(vnode->flags &
((1 << AFS_VNODE_LOCKING) |
(1 << AFS_VNODE_READLOCKED) |
(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
set_bit(AFS_VNODE_LOCKING, &vnode->flags);
spin_unlock(&vnode->lock);
ret = afs_vnode_set_lock(vnode, key, type);
clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
switch (ret) {
case 0:
_debug("acquired");
goto acquired_server_lock;
case -EWOULDBLOCK:
_debug("would block");
spin_lock(&vnode->lock);
ASSERT(list_empty(&vnode->granted_locks));
ASSERTCMP(vnode->pending_locks.next, ==,
&fl->fl_u.afs.link);
goto wait;
default:
spin_lock(&vnode->lock);
list_del_init(&fl->fl_u.afs.link);
spin_unlock(&vnode->lock);
goto error;
}
}
/* otherwise, we need to wait for a local lock to become available */
_debug("wait local");
list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
wait:
if (!(fl->fl_flags & FL_SLEEP)) {
_debug("noblock");
ret = -EAGAIN;
goto abort_attempt;
}
spin_unlock(&vnode->lock);
/* now we need to sleep and wait for the lock manager thread to get the
* lock from the server */
_debug("sleep");
ret = wait_event_interruptible(fl->fl_wait,
fl->fl_u.afs.state <= AFS_LOCK_GRANTED);
if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
ret = fl->fl_u.afs.state;
if (ret < 0)
goto error;
spin_lock(&vnode->lock);
goto given_lock;
}
/* we were interrupted, but someone may still be in the throes of
* giving us the lock */
_debug("intr");
ASSERTCMP(ret, ==, -ERESTARTSYS);
spin_lock(&vnode->lock);
if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
ret = fl->fl_u.afs.state;
if (ret < 0) {
spin_unlock(&vnode->lock);
goto error;
}
goto given_lock;
}
abort_attempt:
/* we aren't going to get the lock, either because we're unwilling to
* wait, or because some signal happened */
_debug("abort");
if (list_empty(&vnode->granted_locks) &&
vnode->pending_locks.next == &fl->fl_u.afs.link) {
if (vnode->pending_locks.prev != &fl->fl_u.afs.link) {
/* kick the next pending lock into having a go */
list_del_init(&fl->fl_u.afs.link);
afs_lock_may_be_available(vnode);
}
} else {
list_del_init(&fl->fl_u.afs.link);
}
spin_unlock(&vnode->lock);
goto error;
acquired_server_lock:
/* we've acquired a server lock, but it needs to be renewed after 5
* mins */
spin_lock(&vnode->lock);
afs_schedule_lock_extension(vnode);
if (type == AFS_LOCK_READ)
set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
else
set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
sharing_existing_lock:
/* the lock has been granted as far as we're concerned... */
fl->fl_u.afs.state = AFS_LOCK_GRANTED;
list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
given_lock:
/* ... but we do still need to get the VFS's blessing */
ASSERT(!(vnode->flags & (1 << AFS_VNODE_LOCKING)));
ASSERT((vnode->flags & ((1 << AFS_VNODE_READLOCKED) |
(1 << AFS_VNODE_WRITELOCKED))) != 0);
ret = posix_lock_file(file, fl, NULL);
if (ret < 0)
goto vfs_rejected_lock;
spin_unlock(&vnode->lock);
/* again, make sure we've got a callback on this file and, again, make
* sure that our view of the data version is up to date (we ignore
* errors incurred here and deal with the consequences elsewhere) */
afs_vnode_fetch_status(vnode, NULL, key);
error:
unlock_flocks();
_leave(" = %d", ret);
return ret;
vfs_rejected_lock:
/* the VFS rejected the lock we just obtained, so we have to discard
* what we just got */
_debug("vfs refused %d", ret);
list_del_init(&fl->fl_u.afs.link);
if (list_empty(&vnode->granted_locks))
afs_defer_unlock(vnode, key);
goto abort_attempt;
}
/*
* unlock on a file on the server
*/
static int afs_do_unlk(struct file *file, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
struct key *key = file->private_data;
int ret;
_enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
/* only whole-file unlocks are supported */
if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
return -EINVAL;
fl->fl_ops = &afs_lock_ops;
INIT_LIST_HEAD(&fl->fl_u.afs.link);
fl->fl_u.afs.state = AFS_LOCK_PENDING;
spin_lock(&vnode->lock);
ret = posix_lock_file(file, fl, NULL);
if (ret < 0) {
spin_unlock(&vnode->lock);
_leave(" = %d [vfs]", ret);
return ret;
}
/* discard the server lock only if all granted locks are gone */
if (list_empty(&vnode->granted_locks))
afs_defer_unlock(vnode, key);
spin_unlock(&vnode->lock);
_leave(" = 0");
return 0;
}
/*
* return information about a lock we currently hold, if indeed we hold one
*/
static int afs_do_getlk(struct file *file, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
struct key *key = file->private_data;
int ret, lock_count;
_enter("");
fl->fl_type = F_UNLCK;
mutex_lock(&vnode->vfs_inode.i_mutex);
/* check local lock records first */
ret = 0;
posix_test_lock(file, fl);
if (fl->fl_type == F_UNLCK) {
/* no local locks; consult the server */
ret = afs_vnode_fetch_status(vnode, NULL, key);
if (ret < 0)
goto error;
lock_count = vnode->status.lock_count;
if (lock_count) {
if (lock_count > 0)
fl->fl_type = F_RDLCK;
else
fl->fl_type = F_WRLCK;
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
}
}
error:
mutex_unlock(&vnode->vfs_inode.i_mutex);
_leave(" = %d [%hd]", ret, fl->fl_type);
return ret;
}
/*
* manage POSIX locks on a file
*/
int afs_lock(struct file *file, int cmd, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
_enter("{%x:%u},%d,{t=%x,fl=%x,r=%Ld:%Ld}",
vnode->fid.vid, vnode->fid.vnode, cmd,
fl->fl_type, fl->fl_flags,
(long long) fl->fl_start, (long long) fl->fl_end);
/* AFS doesn't support mandatory locks */
if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
return -ENOLCK;
if (IS_GETLK(cmd))
return afs_do_getlk(file, fl);
if (fl->fl_type == F_UNLCK)
return afs_do_unlk(file, fl);
return afs_do_setlk(file, fl);
}
/*
* manage FLOCK locks on a file
*/
int afs_flock(struct file *file, int cmd, struct file_lock *fl)
{
struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
_enter("{%x:%u},%d,{t=%x,fl=%x}",
vnode->fid.vid, vnode->fid.vnode, cmd,
fl->fl_type, fl->fl_flags);
/*
* No BSD flocks over NFS allowed.
* Note: we could try to fake a POSIX lock request here by
* using ((u32) filp | 0x80000000) or some such as the pid.
* Not sure whether that would be unique, though, or whether
* that would break in other places.
*/
if (!(fl->fl_flags & FL_FLOCK))
return -ENOLCK;
/* we're simulating flock() locks using posix locks on the server */
fl->fl_owner = (fl_owner_t) file;
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
if (fl->fl_type == F_UNLCK)
return afs_do_unlk(file, fl);
return afs_do_setlk(file, fl);
}
/*
* the POSIX lock management core VFS code copies the lock record and adds the
* copy into its own list, so we need to add that copy to the vnode's lock
* queue in the same place as the original (which will be deleted shortly
* after)
*/
static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl)
{
_enter("");
list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
}
/*
* need to remove this lock from the vnode queue when it's removed from the
* VFS's list
*/
static void afs_fl_release_private(struct file_lock *fl)
{
_enter("");
list_del_init(&fl->fl_u.afs.link);
}