xfs: fix locking in xfs_iget_cache_hit

1/1

Index: linux-2.6/fs/xfs/xfs_iget.c
===================================================================
@@ -133,80 +133,88 @@ xfs_iget_cache_hit(
 	int			flags,
 	int			lock_flags) __releases(pag->pag_ici_lock)
 {
+	struct inode		*inode = VFS_I(ip);
 	struct xfs_mount	*mp = ip->i_mount;
-	int			error = EAGAIN;
+	int			error;
+
+	spin_lock(&ip->i_flags_lock);
 
 	/*
-	 * If INEW is set this inode is being set up
-	 * If IRECLAIM is set this inode is being torn down
-	 * Pause and try again.
+	 * This inode is being torn down, pause and try again.
 	 */
-	if (xfs_iflags_test(ip, (XFS_INEW|XFS_IRECLAIM))) {
+	if (ip->i_flags & XFS_IRECLAIM) {
 		XFS_STATS_INC(xs_ig_frecycle);
+		error = EAGAIN;
 		goto out_error;
 	}
 
-	/* If IRECLAIMABLE is set, we've torn down the vfs inode part */
-	if (xfs_iflags_test(ip, XFS_IRECLAIMABLE)) {
+	/*
+	 * If we are racing with another cache hit that is currently recycling
+	 * this inode out of the XFS_IRECLAIMABLE state, wait for the
+	 * initialisation to complete before continuing.
+	 */
+	if (ip->i_flags & XFS_INEW) {
+		spin_unlock(&ip->i_flags_lock);
+		read_unlock(&pag->pag_ici_lock);
 
-		/*
-		 * If lookup is racing with unlink, then we should return an
-		 * error immediately so we don't remove it from the reclaim
-		 * list and potentially leak the inode.
-		 */
-		if ((ip->i_d.di_mode == 0) && !(flags & XFS_IGET_CREATE)) {
-			error = ENOENT;
-			goto out_error;
-		}
+		XFS_STATS_INC(xs_ig_frecycle);
+		wait_on_inode(inode);
+		return EAGAIN;
+	}
 
+	/*
+	 * If lookup is racing with unlink, then we should return an
+	 * error immediately so we don't remove it from the reclaim
+	 * list and potentially leak the inode.
+	 */
+	if (ip->i_d.di_mode == 0 && !(flags & XFS_IGET_CREATE)) {
+		error = ENOENT;
+		goto out_error;
+	}
+
+	/*
+	 * If IRECLAIMABLE is set, we've torn down the VFS inode already.
+	 * Need to carefully get it back into useable state.
+	 */
+	if (ip->i_flags & XFS_IRECLAIMABLE) {
 		xfs_itrace_exit_tag(ip, "xfs_iget.alloc");
 
 		/*
-		 * We need to re-initialise the VFS inode as it has been
-		 * 'freed' by the VFS. Do this here so we can deal with
-		 * errors cleanly, then tag it so it can be set up correctly
-		 * later.
+		 * We need to set XFS_INEW atomically with clearing the
+		 * reclaimable tag so that we do have an indicator of the
+		 * inode still being initialized.
 		 */
-		if (!inode_init_always(mp->m_super, VFS_I(ip))) {
+		ip->i_flags |= XFS_INEW;
+		__xfs_inode_clear_reclaim_tag(pag, ip);
+
+		spin_unlock(&ip->i_flags_lock);
+		read_unlock(&pag->pag_ici_lock);
+
+		if (unlikely(!inode_init_always(mp->m_super, inode))) {
+			/*
+			 * Re-initializing the inode failed, and we are in deep
+			 * trouble.  Try to re-add it to the reclaim list.
+			 */
+			read_lock(&pag->pag_ici_lock);
+			spin_lock(&ip->i_flags_lock);
+
+			ip->i_flags &= ~XFS_INEW;
+			__xfs_inode_set_reclaim_tag(pag, ip);
+
 			error = ENOMEM;
 			goto out_error;
 		}
-
-		/*
-		 * We must set the XFS_INEW flag before clearing the
-		 * XFS_IRECLAIMABLE flag so that if a racing lookup does
-		 * not find the XFS_IRECLAIMABLE above but has the igrab()
-		 * below succeed we can safely check XFS_INEW to detect
-		 * that this inode is still being initialised.
-		 */
-		xfs_iflags_set(ip, XFS_INEW);
-		xfs_iflags_clear(ip, XFS_IRECLAIMABLE);
-
-		/* clear the radix tree reclaim flag as well. */
-		__xfs_inode_clear_reclaim_tag(mp, pag, ip);
-	} else if (!igrab(VFS_I(ip))) {
+		inode->i_state = I_LOCK|I_NEW;
+	} else {
 		/* If the VFS inode is being torn down, pause and try again. */
-		XFS_STATS_INC(xs_ig_frecycle);
-		goto out_error;
-	} else if (xfs_iflags_test(ip, XFS_INEW)) {
-		/*
-		 * We are racing with another cache hit that is
-		 * currently recycling this inode out of the XFS_IRECLAIMABLE
-		 * state. Wait for the initialisation to complete before
-		 * continuing.
-		 */
-		wait_on_inode(VFS_I(ip));
-	}
+		if (!igrab(inode))
+			goto out_error;
 
-	if (ip->i_d.di_mode == 0 && !(flags & XFS_IGET_CREATE)) {
-		error = ENOENT;
-		iput(VFS_I(ip));
-		goto out_error;
+		/* We've got a live one. */
+		spin_unlock(&ip->i_flags_lock);
+		read_unlock(&pag->pag_ici_lock);
 	}
 
-	/* We've got a live one. */
-	read_unlock(&pag->pag_ici_lock);
-
 	if (lock_flags != 0)
 		xfs_ilock(ip, lock_flags);
 
