xfs: xfs_attr_inactive leaves inconsistent attr fork state behind

commit 6dfe5a04 upstream.

xfs_attr_inactive() is supposed to clean up the attribute fork when
the inode is being freed. While it removes attribute fork extents,
it completely ignores attributes in local format, which means that
there can still be active attributes on the inode after
xfs_attr_inactive() has run.

This leads to problems with concurrent inode writeback - the in-core
inode attribute fork is removed without locking on the assumption
that nothing will be attempting to access the attribute fork after a
call to xfs_attr_inactive() because it isn't supposed to exist on
disk any more.

To fix this, make xfs_attr_inactive() completely remove all traces
of the attribute fork from the inode, regardless of it's state.
Further, also remove the in-core attribute fork structure safely so
that there is nothing further that needs to be done by callers to
clean up the attribute fork. This means we can remove the in-core
and on-disk attribute forks atomically.

Also, on error simply remove the in-memory attribute fork. There's
nothing that can be done with it once we have failed to remove the
on-disk attribute fork, so we may as well just blow it away here
anyway.
Reported-by: Waiman Long <waiman.long@hp.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
[ luis: backported to 3.16:
  - no libxfs in 3.16, xfs_attr_leaf.{c,h} in fs/xfs/ dir
  - adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

fs/xfs/xfs_attr_inactive.c

@@ -382,23 +382,31 @@ xfs_attr3_root_inactive(
 	return error;
 }
 
+/*
+ * xfs_attr_inactive kills all traces of an attribute fork on an inode. It
+ * removes both the on-disk and in-memory inode fork. Note that this also has to
+ * handle the condition of inodes without attributes but with an attribute fork
+ * configured, so we can't use xfs_inode_hasattr() here.
+ *
+ * The in-memory attribute fork is removed even on error.
+ */
 int
-xfs_attr_inactive(xfs_inode_t *dp)
+xfs_attr_inactive(
+	struct xfs_inode	*dp)
 {
-	xfs_trans_t *trans;
-	xfs_mount_t *mp;
-	int error;
+	struct xfs_trans	*trans;
+	struct xfs_mount	*mp;
+	int			cancel_flags = 0;
+	int			lock_mode = XFS_ILOCK_SHARED;
+	int			error = 0;
 
 	mp = dp->i_mount;
 	ASSERT(! XFS_NOT_DQATTACHED(mp, dp));
 
-	xfs_ilock(dp, XFS_ILOCK_SHARED);
-	if (!xfs_inode_hasattr(dp) ||
-	    dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL) {
-		xfs_iunlock(dp, XFS_ILOCK_SHARED);
-		return 0;
-	}
-	xfs_iunlock(dp, XFS_ILOCK_SHARED);
+	xfs_ilock(dp, lock_mode);
+	if (!XFS_IFORK_Q(dp))
+		goto out_destroy_fork;
+	xfs_iunlock(dp, lock_mode);
 
 	/*
 	 * Start our first transaction of the day.
@@ -410,13 +418,18 @@ xfs_attr_inactive(xfs_inode_t *dp)
 	 * the inode in every transaction to let it float upward through
 	 * the log.
 	 */
+	lock_mode = 0;
 	trans = xfs_trans_alloc(mp, XFS_TRANS_ATTRINVAL);
 	error = xfs_trans_reserve(trans, &M_RES(mp)->tr_attrinval, 0, 0);
-	if (error) {
-		xfs_trans_cancel(trans, 0);
-		return(error);
-	}
-	xfs_ilock(dp, XFS_ILOCK_EXCL);
+	if (error)
+		goto out_cancel;
+
+	lock_mode = XFS_ILOCK_EXCL;
+	cancel_flags = XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT;
+	xfs_ilock(dp, lock_mode);
+
+	if (!XFS_IFORK_Q(dp))
+		goto out_cancel;
 
 	/*
 	 * No need to make quota reservations here. We expect to release some
@@ -424,29 +437,31 @@ xfs_attr_inactive(xfs_inode_t *dp)
 	 */
 	xfs_trans_ijoin(trans, dp, 0);
 
-	/*
-	 * Decide on what work routines to call based on the inode size.
-	 */
-	if (!xfs_inode_hasattr(dp) ||
-	    dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL) {
-		error = 0;
-		goto out;
+	/* invalidate and truncate the attribute fork extents */
+	if (dp->i_d.di_aformat != XFS_DINODE_FMT_LOCAL) {
+		error = xfs_attr3_root_inactive(&trans, dp);
+		if (error)
+			goto out_cancel;
+
+		error = xfs_itruncate_extents(&trans, dp, XFS_ATTR_FORK, 0);
+		if (error)
+			goto out_cancel;
 	}
-	error = xfs_attr3_root_inactive(&trans, dp);
-	if (error)
-		goto out;
 
-	error = xfs_itruncate_extents(&trans, dp, XFS_ATTR_FORK, 0);
-	if (error)
-		goto out;
+	/* Reset the attribute fork - this also destroys the in-core fork */
+	xfs_attr_fork_remove(dp, trans);
 
 	error = xfs_trans_commit(trans, XFS_TRANS_RELEASE_LOG_RES);
-	xfs_iunlock(dp, XFS_ILOCK_EXCL);
-
+	xfs_iunlock(dp, lock_mode);
 	return(error);
 
-out:
-	xfs_trans_cancel(trans, XFS_TRANS_RELEASE_LOG_RES|XFS_TRANS_ABORT);
-	xfs_iunlock(dp, XFS_ILOCK_EXCL);
+out_cancel:
+	xfs_trans_cancel(trans, cancel_flags);
+out_destroy_fork:
+	/* kill the in-core attr fork before we drop the inode lock */
+	if (dp->i_afp)
+		xfs_idestroy_fork(dp, XFS_ATTR_FORK);
+	if (lock_mode)
+		xfs_iunlock(dp, lock_mode);
 	return(error);
 }

fs/xfs/xfs_attr_leaf.c

@@ -500,8 +500,8 @@ xfs_attr_shortform_add(xfs_da_args_t *args, int forkoff)
  * After the last attribute is removed revert to original inode format,
  * making all literal area available to the data fork once more.
  */
-STATIC void
-xfs_attr_fork_reset(
+void
+xfs_attr_fork_remove(
 	struct xfs_inode	*ip,
 	struct xfs_trans	*tp)
 {
@@ -567,7 +567,7 @@ xfs_attr_shortform_remove(xfs_da_args_t *args)
 	    (mp->m_flags & XFS_MOUNT_ATTR2) &&
 	    (dp->i_d.di_format != XFS_DINODE_FMT_BTREE) &&
 	    !(args->op_flags & XFS_DA_OP_ADDNAME)) {
-		xfs_attr_fork_reset(dp, args->trans);
+		xfs_attr_fork_remove(dp, args->trans);
 	} else {
 		xfs_idata_realloc(dp, -size, XFS_ATTR_FORK);
 		dp->i_d.di_forkoff = xfs_attr_shortform_bytesfit(dp, totsize);
@@ -830,7 +830,7 @@ xfs_attr3_leaf_to_shortform(
 	if (forkoff == -1) {
 		ASSERT(dp->i_mount->m_flags & XFS_MOUNT_ATTR2);
 		ASSERT(dp->i_d.di_format != XFS_DINODE_FMT_BTREE);
-		xfs_attr_fork_reset(dp, args->trans);
+		xfs_attr_fork_remove(dp, args->trans);
 		goto out;
 	}
 

fs/xfs/xfs_attr_leaf.h

@@ -53,7 +53,7 @@ int	xfs_attr_shortform_remove(struct xfs_da_args *args);
 int	xfs_attr_shortform_list(struct xfs_attr_list_context *context);
 int	xfs_attr_shortform_allfit(struct xfs_buf *bp, struct xfs_inode *dp);
 int	xfs_attr_shortform_bytesfit(xfs_inode_t *dp, int bytes);
-
+void	xfs_attr_fork_remove(struct xfs_inode *ip, struct xfs_trans *tp);
 
 /*
  * Internal routines when attribute fork size == XFS_LBSIZE(mp).

fs/xfs/xfs_inode.c

@@ -1890,21 +1890,17 @@ xfs_inactive(
 	/*
 	 * If there are attributes associated with the file then blow them away
 	 * now.  The code calls a routine that recursively deconstructs the
-	 * attribute fork.  We need to just commit the current transaction
-	 * because we can't use it for xfs_attr_inactive().
+	 * attribute fork. If also blows away the in-core attribute fork.
 	 */
-	if (ip->i_d.di_anextents > 0) {
-		ASSERT(ip->i_d.di_forkoff != 0);
-
+	if (XFS_IFORK_Q(ip)) {
 		error = xfs_attr_inactive(ip);
 		if (error)
 			return;
 	}
 
-	if (ip->i_afp)
-		xfs_idestroy_fork(ip, XFS_ATTR_FORK);
-
+	ASSERT(!ip->i_afp);
 	ASSERT(ip->i_d.di_anextents == 0);
+	ASSERT(ip->i_d.di_forkoff == 0);
 
 	/*
 	 * Free the inode.