AFS: fix file locking
Fix file locking for AFS: (*) Start the lock manager thread under a mutex to avoid a race. (*) Made the locking non-fair: New readlocks will jump pending writelocks if there's a readlock currently granted on a file. This makes the behaviour similar to Linux's VFS locking. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Родитель
b34bd06e48
Коммит
ff8e210a95
128
fs/afs/flock.c
128
fs/afs/flock.c
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@ -19,6 +19,7 @@ static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
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static void afs_fl_release_private(struct file_lock *fl);
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static struct workqueue_struct *afs_lock_manager;
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static DEFINE_MUTEX(afs_lock_manager_mutex);
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static struct file_lock_operations afs_lock_ops = {
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.fl_copy_lock = afs_fl_copy_lock,
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@ -30,12 +31,20 @@ static struct file_lock_operations afs_lock_ops = {
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*/
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static int afs_init_lock_manager(void)
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{
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int ret;
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ret = 0;
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if (!afs_lock_manager) {
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afs_lock_manager = create_singlethread_workqueue("kafs_lockd");
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if (!afs_lock_manager)
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return -ENOMEM;
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mutex_lock(&afs_lock_manager_mutex);
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if (!afs_lock_manager) {
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afs_lock_manager =
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create_singlethread_workqueue("kafs_lockd");
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if (!afs_lock_manager)
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ret = -ENOMEM;
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}
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mutex_unlock(&afs_lock_manager_mutex);
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}
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return 0;
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return ret;
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}
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/*
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@ -67,6 +76,29 @@ static void afs_schedule_lock_extension(struct afs_vnode *vnode)
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AFS_LOCKWAIT * HZ / 2);
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}
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/*
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* grant one or more locks (readlocks are allowed to jump the queue if the
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* first lock in the queue is itself a readlock)
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* - the caller must hold the vnode lock
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*/
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static void afs_grant_locks(struct afs_vnode *vnode, struct file_lock *fl)
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{
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struct file_lock *p, *_p;
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list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
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if (fl->fl_type == F_RDLCK) {
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list_for_each_entry_safe(p, _p, &vnode->pending_locks,
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fl_u.afs.link) {
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if (p->fl_type == F_RDLCK) {
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p->fl_u.afs.state = AFS_LOCK_GRANTED;
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list_move_tail(&p->fl_u.afs.link,
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&vnode->granted_locks);
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wake_up(&p->fl_wait);
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}
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}
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}
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}
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/*
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* do work for a lock, including:
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* - probing for a lock we're waiting on but didn't get immediately
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@ -172,8 +204,7 @@ void afs_lock_work(struct work_struct *work)
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struct file_lock, fl_u.afs.link) == fl) {
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fl->fl_u.afs.state = ret;
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if (ret == AFS_LOCK_GRANTED)
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list_move_tail(&fl->fl_u.afs.link,
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&vnode->granted_locks);
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afs_grant_locks(vnode, fl);
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else
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list_del_init(&fl->fl_u.afs.link);
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wake_up(&fl->fl_wait);
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@ -258,49 +289,50 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
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spin_lock(&vnode->lock);
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if (list_empty(&vnode->pending_locks)) {
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/* if there's no-one else with a lock on this vnode, then we
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* need to ask the server for a lock */
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if (list_empty(&vnode->granted_locks)) {
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_debug("not locked");
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ASSERTCMP(vnode->flags &
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((1 << AFS_VNODE_LOCKING) |
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(1 << AFS_VNODE_READLOCKED) |
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(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
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list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
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set_bit(AFS_VNODE_LOCKING, &vnode->flags);
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/* if we've already got a readlock on the server then we can instantly
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* grant another readlock, irrespective of whether there are any
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* pending writelocks */
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if (type == AFS_LOCK_READ &&
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vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
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_debug("instant readlock");
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ASSERTCMP(vnode->flags &
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((1 << AFS_VNODE_LOCKING) |
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(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
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ASSERT(!list_empty(&vnode->granted_locks));
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goto sharing_existing_lock;
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}
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/* if there's no-one else with a lock on this vnode, then we need to
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* ask the server for a lock */
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if (list_empty(&vnode->pending_locks) &&
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list_empty(&vnode->granted_locks)) {
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_debug("not locked");
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ASSERTCMP(vnode->flags &
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((1 << AFS_VNODE_LOCKING) |
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(1 << AFS_VNODE_READLOCKED) |
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(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
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list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
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set_bit(AFS_VNODE_LOCKING, &vnode->flags);
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spin_unlock(&vnode->lock);
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ret = afs_vnode_set_lock(vnode, key, type);
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clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
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switch (ret) {
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case 0:
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_debug("acquired");
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goto acquired_server_lock;
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case -EWOULDBLOCK:
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_debug("would block");
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spin_lock(&vnode->lock);
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ASSERT(list_empty(&vnode->granted_locks));
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ASSERTCMP(vnode->pending_locks.next, ==,
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&fl->fl_u.afs.link);
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goto wait;
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default:
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spin_lock(&vnode->lock);
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list_del_init(&fl->fl_u.afs.link);
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spin_unlock(&vnode->lock);
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ret = afs_vnode_set_lock(vnode, key, type);
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clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
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switch (ret) {
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case 0:
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goto acquired_server_lock;
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case -EWOULDBLOCK:
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spin_lock(&vnode->lock);
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ASSERT(list_empty(&vnode->granted_locks));
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ASSERTCMP(vnode->pending_locks.next, ==,
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&fl->fl_u.afs.link);
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goto wait;
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default:
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spin_lock(&vnode->lock);
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list_del_init(&fl->fl_u.afs.link);
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spin_unlock(&vnode->lock);
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goto error;
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}
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}
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/* if we've already got a readlock on the server and no waiting
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* writelocks, then we might be able to instantly grant another
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* readlock */
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if (type == AFS_LOCK_READ &&
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vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
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_debug("instant readlock");
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ASSERTCMP(vnode->flags &
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((1 << AFS_VNODE_LOCKING) |
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(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
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ASSERT(!list_empty(&vnode->granted_locks));
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goto sharing_existing_lock;
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goto error;
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}
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}
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