afs: Handle lock rpc ops failing on a file that got deleted

Holding a file lock on an AFS file does not prevent it from being deleted
on the server, so we need to handle an error resulting from that when we
try setting, extending or releasing a lock.

Fix this by adding a "deleted" lock state and cancelling the lock extension
process for that file and aborting all waiters for the lock.

Fixes: 0fafdc9f ("afs: Fix file locking")
Reported-by: Jonathan Billings <jsbillin@umich.edu>
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/flock.c

@@ -157,6 +157,28 @@ static void afs_next_locker(struct afs_vnode *vnode, int error)
 	_leave("");
 }
 
+/*
+ * Kill off all waiters in the the pending lock queue due to the vnode being
+ * deleted.
+ */
+static void afs_kill_lockers_enoent(struct afs_vnode *vnode)
+{
+	struct file_lock *p;
+
+	afs_set_lock_state(vnode, AFS_VNODE_LOCK_DELETED);
+
+	while (!list_empty(&vnode->pending_locks)) {
+		p = list_entry(vnode->pending_locks.next,
+			       struct file_lock, fl_u.afs.link);
+		list_del_init(&p->fl_u.afs.link);
+		p->fl_u.afs.state = -ENOENT;
+		wake_up(&p->fl_wait);
+	}
+
+	key_put(vnode->lock_key);
+	vnode->lock_key = NULL;
+}
+
 /*
  * Get a lock on a file
  */
@@ -278,13 +300,19 @@ void afs_lock_work(struct work_struct *work)
 		/* 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)
+		if (ret < 0) {
+			trace_afs_flock_ev(vnode, NULL, afs_flock_release_fail,
+					   ret);
 			printk(KERN_WARNING "AFS:"
 			       " Failed to release lock on {%llx:%llx} error %d\n",
 			       vnode->fid.vid, vnode->fid.vnode, ret);
+		}
 
 		spin_lock(&vnode->lock);
-		afs_next_locker(vnode, 0);
+		if (ret == -ENOENT)
+			afs_kill_lockers_enoent(vnode);
+		else
+			afs_next_locker(vnode, 0);
 		spin_unlock(&vnode->lock);
 		return;
 
@@ -304,12 +332,21 @@ void afs_lock_work(struct work_struct *work)
 		ret = afs_extend_lock(vnode, key); /* RPC */
 		key_put(key);
 
-		if (ret < 0)
+		if (ret < 0) {
+			trace_afs_flock_ev(vnode, NULL, afs_flock_extend_fail,
+					   ret);
 			pr_warning("AFS: Failed to extend lock on {%llx:%llx} error %d\n",
 				   vnode->fid.vid, vnode->fid.vnode, ret);
+		}
 
 		spin_lock(&vnode->lock);
 
+		if (ret == -ENOENT) {
+			afs_kill_lockers_enoent(vnode);
+			spin_unlock(&vnode->lock);
+			return;
+		}
+
 		if (vnode->lock_state != AFS_VNODE_LOCK_EXTENDING)
 			goto again;
 		afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);
@@ -333,6 +370,11 @@ void afs_lock_work(struct work_struct *work)
 		spin_unlock(&vnode->lock);
 		return;
 
+	case AFS_VNODE_LOCK_DELETED:
+		afs_kill_lockers_enoent(vnode);
+		spin_unlock(&vnode->lock);
+		return;
+
 	default:
 		/* Looks like a lock request was withdrawn. */
 		spin_unlock(&vnode->lock);
@@ -435,6 +477,10 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
 	spin_lock(&vnode->lock);
 	list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
 
+	ret = -ENOENT;
+	if (vnode->lock_state == AFS_VNODE_LOCK_DELETED)
+		goto error_unlock;
+
 	/* If we've already got a lock on the server then try to move to having
 	 * the VFS grant the requested lock.  Note that this means that other
 	 * clients may get starved out.
@@ -489,6 +535,13 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
 		afs_next_locker(vnode, ret);
 		goto error_unlock;
 
+	case -ENOENT:
+		fl->fl_u.afs.state = ret;
+		trace_afs_flock_ev(vnode, fl, afs_flock_fail_other, ret);
+		list_del_init(&fl->fl_u.afs.link);
+		afs_kill_lockers_enoent(vnode);
+		goto error_unlock;
+
 	default:
 		fl->fl_u.afs.state = ret;
 		trace_afs_flock_ev(vnode, fl, afs_flock_fail_other, ret);
@@ -638,6 +691,9 @@ static int afs_do_getlk(struct file *file, struct file_lock *fl)
 
 	_enter("");
 
+	if (vnode->lock_state == AFS_VNODE_LOCK_DELETED)
+		return -ENOENT;
+
 	fl->fl_type = F_UNLCK;
 
 	/* check local lock records first */

fs/afs/internal.h

@@ -599,6 +599,7 @@ enum afs_lock_state {
 	AFS_VNODE_LOCK_EXTENDING,	/* We're extending a lock on the server */
 	AFS_VNODE_LOCK_NEED_UNLOCK,	/* We need to unlock on the server */
 	AFS_VNODE_LOCK_UNLOCKING,	/* We're telling the server to unlock */
+	AFS_VNODE_LOCK_DELETED,		/* The vnode has been deleted whilst we have a lock */
 };
 
 /*

include/trace/events/afs.h

@@ -156,9 +156,11 @@ enum afs_flock_event {
 	afs_flock_acquired,
 	afs_flock_callback_break,
 	afs_flock_defer_unlock,
+	afs_flock_extend_fail,
 	afs_flock_fail_other,
 	afs_flock_fail_perm,
 	afs_flock_no_lockers,
+	afs_flock_release_fail,
 	afs_flock_timestamp,
 	afs_flock_try_to_lock,
 	afs_flock_vfs_lock,
@@ -323,15 +325,18 @@ enum afs_flock_operation {
 	EM(AFS_VNODE_LOCK_GRANTED,		"GRANTED")		\
 	EM(AFS_VNODE_LOCK_EXTENDING,		"EXTENDING")		\
 	EM(AFS_VNODE_LOCK_NEED_UNLOCK,		"NEED_UNLOCK")		\
-	E_(AFS_VNODE_LOCK_UNLOCKING,		"UNLOCKING")		\
+	EM(AFS_VNODE_LOCK_UNLOCKING,		"UNLOCKING")		\
+	E_(AFS_VNODE_LOCK_DELETED,		"DELETED")
 
 #define afs_flock_events						\
 	EM(afs_flock_acquired,			"Acquired")		\
 	EM(afs_flock_callback_break,		"Callback")		\
 	EM(afs_flock_defer_unlock,		"D-Unlock")		\
+	EM(afs_flock_extend_fail,		"Ext_Fail")		\
 	EM(afs_flock_fail_other,		"ErrOther")		\
 	EM(afs_flock_fail_perm,			"ErrPerm ")		\
 	EM(afs_flock_no_lockers,		"NoLocker")		\
+	EM(afs_flock_release_fail,		"Rel_Fail")		\
 	EM(afs_flock_timestamp,			"Timestmp")		\
 	EM(afs_flock_try_to_lock,		"TryToLck")		\
 	EM(afs_flock_vfs_lock,			"VFSLock ")		\