linux/fs/afs/flock.c

717 lines
19 KiB
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
struct workqueue_struct *afs_lock_manager;
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 const struct file_lock_operations afs_lock_ops = {
.fl_copy_lock = afs_fl_copy_lock,
.fl_release_private = afs_fl_release_private,
};
/*
* 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);
}
}
}
}
/*
* Get a lock on a file
*/
static int afs_set_lock(struct afs_vnode *vnode, struct key *key,
afs_lock_type_t type)
{
struct afs_fs_cursor fc;
int ret;
_enter("%s{%x:%u.%u},%x,%u",
vnode->volume->name,
vnode->fid.vid,
vnode->fid.vnode,
vnode->fid.unique,
key_serial(key), type);
ret = -ERESTARTSYS;
if (afs_begin_vnode_operation(&fc, vnode, key)) {
while (afs_select_fileserver(&fc)) {
fc.cb_break = vnode->cb_break + vnode->cb_s_break;
afs_fs_set_lock(&fc, type);
}
afs_check_for_remote_deletion(&fc, fc.vnode);
afs_vnode_commit_status(&fc, vnode, fc.cb_break);
ret = afs_end_vnode_operation(&fc);
}
_leave(" = %d", ret);
return ret;
}
/*
* Extend a lock on a file
*/
static int afs_extend_lock(struct afs_vnode *vnode, struct key *key)
{
struct afs_fs_cursor fc;
int ret;
_enter("%s{%x:%u.%u},%x",
vnode->volume->name,
vnode->fid.vid,
vnode->fid.vnode,
vnode->fid.unique,
key_serial(key));
ret = -ERESTARTSYS;
if (afs_begin_vnode_operation(&fc, vnode, key)) {
while (afs_select_current_fileserver(&fc)) {
fc.cb_break = vnode->cb_break + vnode->cb_s_break;
afs_fs_extend_lock(&fc);
}
afs_check_for_remote_deletion(&fc, fc.vnode);
afs_vnode_commit_status(&fc, vnode, fc.cb_break);
ret = afs_end_vnode_operation(&fc);
}
_leave(" = %d", ret);
return ret;
}
/*
* Release a lock on a file
*/
static int afs_release_lock(struct afs_vnode *vnode, struct key *key)
{
struct afs_fs_cursor fc;
int ret;
_enter("%s{%x:%u.%u},%x",
vnode->volume->name,
vnode->fid.vid,
vnode->fid.vnode,
vnode->fid.unique,
key_serial(key));
ret = -ERESTARTSYS;
if (afs_begin_vnode_operation(&fc, vnode, key)) {
while (afs_select_current_fileserver(&fc)) {
fc.cb_break = vnode->cb_break + vnode->cb_s_break;
afs_fs_release_lock(&fc);
}
afs_check_for_remote_deletion(&fc, fc.vnode);
afs_vnode_commit_status(&fc, vnode, fc.cb_break);
ret = afs_end_vnode_operation(&fc);
}
_leave(" = %d", ret);
return ret;
}
/*
* 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, *next;
afs_lock_type_t type;
struct key *key;
int ret;
_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
spin_lock(&vnode->lock);
again:
_debug("wstate %u for %p", vnode->lock_state, vnode);
switch (vnode->lock_state) {
case AFS_VNODE_LOCK_NEED_UNLOCK:
_debug("unlock");
vnode->lock_state = AFS_VNODE_LOCK_UNLOCKING;
spin_unlock(&vnode->lock);
/* attempt to release the server lock; if it fails, we just
* wait 5 minutes and it'll expire anyway */
ret = afs_release_lock(vnode, vnode->lock_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->lock_key);
vnode->lock_key = NULL;
vnode->lock_state = AFS_VNODE_LOCK_NONE;
if (list_empty(&vnode->pending_locks)) {
spin_unlock(&vnode->lock);
return;
}
/* The new front of the queue now owns the state variables. */
next = list_entry(vnode->pending_locks.next,
struct file_lock, fl_u.afs.link);
vnode->lock_key = afs_file_key(next->fl_file);
vnode->lock_type = (next->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
vnode->lock_state = AFS_VNODE_LOCK_WAITING_FOR_CB;
goto again;
/* If we've already got a lock, then it must be time to extend that
* lock as AFS locks time out after 5 minutes.
*/
case AFS_VNODE_LOCK_GRANTED:
_debug("extend");
ASSERT(!list_empty(&vnode->granted_locks));
key = key_get(vnode->lock_key);
vnode->lock_state = AFS_VNODE_LOCK_EXTENDING;
spin_unlock(&vnode->lock);
ret = afs_extend_lock(vnode, key); /* RPC */
key_put(key);
if (ret < 0)
pr_warning("AFS: Failed to extend lock on {%x:%x} error %d\n",
vnode->fid.vid, vnode->fid.vnode, ret);
spin_lock(&vnode->lock);
if (vnode->lock_state != AFS_VNODE_LOCK_EXTENDING)
goto again;
vnode->lock_state = AFS_VNODE_LOCK_GRANTED;
if (ret == 0)
afs_schedule_lock_extension(vnode);
else
queue_delayed_work(afs_lock_manager, &vnode->lock_work,
HZ * 10);
spin_unlock(&vnode->lock);
_leave(" [ext]");
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.
*/
case AFS_VNODE_LOCK_WAITING_FOR_CB:
_debug("get");
key = key_get(vnode->lock_key);
type = vnode->lock_type;
vnode->lock_state = AFS_VNODE_LOCK_SETTING;
spin_unlock(&vnode->lock);
ret = afs_set_lock(vnode, key, type); /* RPC */
key_put(key);
spin_lock(&vnode->lock);
switch (ret) {
case -EWOULDBLOCK:
_debug("blocked");
break;
case 0:
_debug("acquired");
vnode->lock_state = AFS_VNODE_LOCK_GRANTED;
/* Fall through */
default:
/* Pass the lock or the error onto the first locker in
* the list - if they're looking for this type of lock.
* If they're not, we assume that whoever asked for it
* took a signal.
*/
if (list_empty(&vnode->pending_locks)) {
_debug("withdrawn");
vnode->lock_state = AFS_VNODE_LOCK_NEED_UNLOCK;
goto again;
}
fl = list_entry(vnode->pending_locks.next,
struct file_lock, fl_u.afs.link);
type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
if (vnode->lock_type != type) {
_debug("changed");
vnode->lock_state = AFS_VNODE_LOCK_NEED_UNLOCK;
goto again;
}
fl->fl_u.afs.state = ret;
if (ret == 0)
afs_grant_locks(vnode, fl);
else
list_del_init(&fl->fl_u.afs.link);
wake_up(&fl->fl_wait);
spin_unlock(&vnode->lock);
_leave(" [granted]");
return;
}
default:
/* Looks like a lock request was withdrawn. */
spin_unlock(&vnode->lock);
_leave(" [no]");
return;
}
}
/*
* 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)
{
_enter("");
if (vnode->lock_state == AFS_VNODE_LOCK_GRANTED ||
vnode->lock_state == AFS_VNODE_LOCK_EXTENDING) {
cancel_delayed_work(&vnode->lock_work);
vnode->lock_state = AFS_VNODE_LOCK_NEED_UNLOCK;
afs_lock_may_be_available(vnode);
}
}
/*
* Check that our view of the file metadata is up to date and check to see
* whether we think that we have a locking permit.
*/
static int afs_do_setlk_check(struct afs_vnode *vnode, struct key *key,
afs_lock_type_t type, bool can_sleep)
{
afs_access_t access;
int ret;
/* Make sure we've got a callback on this file and that our view of the
* data version is up to date.
*/
ret = afs_validate(vnode, key);
if (ret < 0)
return ret;
/* Check the permission set to see if we're actually going to be
* allowed to get a lock on this file.
*/
ret = afs_check_permit(vnode, key, &access);
if (ret < 0)
return ret;
/* At a rough estimation, you need LOCK, WRITE or INSERT perm to
* read-lock a file and WRITE or INSERT perm to write-lock a file.
*
* We can't rely on the server to do this for us since if we want to
* share a read lock that we already have, we won't go the server.
*/
if (type == AFS_LOCK_READ) {
if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE | AFS_ACE_LOCK)))
return -EACCES;
if (vnode->status.lock_count == -1 && !can_sleep)
return -EAGAIN; /* Write locked */
} else {
if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE)))
return -EACCES;
if (vnode->status.lock_count != 0 && !can_sleep)
return -EAGAIN; /* Locked */
}
return 0;
}
/*
* Remove the front runner from the pending queue.
* - The caller must hold vnode->lock.
*/
static void afs_dequeue_lock(struct afs_vnode *vnode, struct file_lock *fl)
{
struct file_lock *next;
_enter("");
/* ->lock_type, ->lock_key and ->lock_state only belong to this
* file_lock if we're at the front of the pending queue or if we have
* the lock granted or if the lock_state is NEED_UNLOCK or UNLOCKING.
*/
if (vnode->granted_locks.next == &fl->fl_u.afs.link &&
vnode->granted_locks.prev == &fl->fl_u.afs.link) {
list_del_init(&fl->fl_u.afs.link);
afs_defer_unlock(vnode);
return;
}
if (!list_empty(&vnode->granted_locks) ||
vnode->pending_locks.next != &fl->fl_u.afs.link) {
list_del_init(&fl->fl_u.afs.link);
return;
}
list_del_init(&fl->fl_u.afs.link);
key_put(vnode->lock_key);
vnode->lock_key = NULL;
vnode->lock_state = AFS_VNODE_LOCK_NONE;
if (list_empty(&vnode->pending_locks))
return;
/* The new front of the queue now owns the state variables. */
next = list_entry(vnode->pending_locks.next,
struct file_lock, fl_u.afs.link);
vnode->lock_key = afs_file_key(next->fl_file);
vnode->lock_type = (next->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
vnode->lock_state = AFS_VNODE_LOCK_WAITING_FOR_CB;
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 inode *inode = locks_inode(file);
struct afs_vnode *vnode = AFS_FS_I(inode);
afs_lock_type_t type;
struct key *key = afs_file_key(file);
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;
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;
ret = afs_do_setlk_check(vnode, key, type, fl->fl_flags & FL_SLEEP);
if (ret < 0)
return ret;
spin_lock(&vnode->lock);
/* If we've already got a readlock on the server then we instantly
* grant another readlock, irrespective of whether there are any
* pending writelocks.
*/
if (type == AFS_LOCK_READ &&
vnode->lock_state == AFS_VNODE_LOCK_GRANTED &&
vnode->lock_type == AFS_LOCK_READ) {
_debug("instant readlock");
ASSERT(!list_empty(&vnode->granted_locks));
goto share_existing_lock;
}
list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
goto need_to_wait;
/* We don't have a lock on this vnode and we aren't currently waiting
* for one either, so ask the server for a lock.
*
* Note that we need to be careful if we get interrupted by a signal
* after dispatching the request as we may still get the lock, even
* though we don't wait for the reply (it's not too bad a problem - the
* lock will expire in 10 mins anyway).
*/
_debug("not locked");
vnode->lock_key = key_get(key);
vnode->lock_type = type;
vnode->lock_state = AFS_VNODE_LOCK_SETTING;
spin_unlock(&vnode->lock);
ret = afs_set_lock(vnode, key, type); /* RPC */
spin_lock(&vnode->lock);
switch (ret) {
default:
goto abort_attempt;
case -EWOULDBLOCK:
/* The server doesn't have a lock-waiting queue, so the client
* will have to retry. The server will break the outstanding
* callbacks on a file when a lock is released.
*/
_debug("would block");
ASSERT(list_empty(&vnode->granted_locks));
ASSERTCMP(vnode->pending_locks.next, ==, &fl->fl_u.afs.link);
vnode->lock_state = AFS_VNODE_LOCK_WAITING_FOR_CB;
goto need_to_wait;
case 0:
_debug("acquired");
break;
}
/* we've acquired a server lock, but it needs to be renewed after 5
* mins */
vnode->lock_state = AFS_VNODE_LOCK_GRANTED;
afs_schedule_lock_extension(vnode);
share_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 */
spin_unlock(&vnode->lock);
ret = posix_lock_file(file, fl, NULL);
if (ret < 0)
goto vfs_rejected_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_validate(vnode, key);
_leave(" = 0");
return 0;
need_to_wait:
/* We're going to have to wait. Either this client doesn't have a lock
* on the server yet and we need to wait for a callback to occur, or
* the client does have a lock on the server, but it belongs to some
* other process(es) and is incompatible with the lock we want.
*/
ret = -EAGAIN;
if (fl->fl_flags & FL_SLEEP) {
spin_unlock(&vnode->lock);
_debug("sleep");
ret = wait_event_interruptible(fl->fl_wait,
fl->fl_u.afs.state != AFS_LOCK_PENDING);
spin_lock(&vnode->lock);
}
if (fl->fl_u.afs.state == AFS_LOCK_GRANTED)
goto given_lock;
if (fl->fl_u.afs.state < 0)
ret = fl->fl_u.afs.state;
abort_attempt:
/* we aren't going to get the lock, either because we're unwilling to
* wait, or because some signal happened */
_debug("abort");
afs_dequeue_lock(vnode, fl);
error_unlock:
spin_unlock(&vnode->lock);
_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. We defer this to the lock manager work item to
* deal with.
*/
_debug("vfs refused %d", ret);
spin_lock(&vnode->lock);
list_del_init(&fl->fl_u.afs.link);
if (list_empty(&vnode->granted_locks))
afs_defer_unlock(vnode);
goto error_unlock;
}
/*
* 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(locks_inode(file));
int ret;
_enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
/* Flush all pending writes before doing anything with locks. */
vfs_fsync(file, 0);
/* only whole-file unlocks are supported */
if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
return -EINVAL;
ret = posix_lock_file(file, fl, NULL);
_leave(" = %d [%u]", ret, vnode->lock_state);
return ret;
}
/*
* 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(locks_inode(file));
struct key *key = afs_file_key(file);
int ret, lock_count;
_enter("");
fl->fl_type = F_UNLCK;
/* check local lock records first */
posix_test_lock(file, fl);
if (fl->fl_type == F_UNLCK) {
/* no local locks; consult the server */
ret = afs_fetch_status(vnode, key, false);
if (ret < 0)
goto error;
lock_count = READ_ONCE(vnode->status.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;
}
ret = 0;
error:
_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(locks_inode(file));
_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(locks_inode(file));
_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 */
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)
{
struct afs_vnode *vnode = AFS_FS_I(locks_inode(fl->fl_file));
_enter("");
spin_lock(&vnode->lock);
list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
spin_unlock(&vnode->lock);
}
/*
* 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)
{
struct afs_vnode *vnode = AFS_FS_I(locks_inode(fl->fl_file));
_enter("");
spin_lock(&vnode->lock);
afs_dequeue_lock(vnode, fl);
_debug("state %u for %p", vnode->lock_state, vnode);
spin_unlock(&vnode->lock);
}