xfs: make xattri_leaf_bp more useful

We currently set it and hold it when converting from short to leaf
form, then release it only to immediately look it back up again
to do the leaf insert.

Do a bit of refactoring to xfs_attr_leaf_try_add() to avoid this
messy handling of the newly allocated leaf buffer.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson<allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_attr.c

@@ -318,7 +318,15 @@ xfs_attr_leaf_addname(
 	int			error;
 
 	if (xfs_attr_is_leaf(dp)) {
+
+		/*
+		 * Use the leaf buffer we may already hold locked as a result of
+		 * a sf-to-leaf conversion. The held buffer is no longer valid
+		 * after this call, regardless of the result.
+		 */
 		error = xfs_attr_leaf_try_add(args, attr->xattri_leaf_bp);
+		attr->xattri_leaf_bp = NULL;
+
 		if (error == -ENOSPC) {
 			error = xfs_attr3_leaf_to_node(args);
 			if (error)
@@ -340,6 +348,8 @@ xfs_attr_leaf_addname(
 		}
 		next_state = XFS_DAS_FOUND_LBLK;
 	} else {
+		ASSERT(!attr->xattri_leaf_bp);
+
 		error = xfs_attr_node_addname_find_attr(attr);
 		if (error)
 			return error;
@@ -395,12 +405,6 @@ xfs_attr_set_iter(
 		 */
 		if (xfs_attr_is_shortform(dp))
 			return xfs_attr_sf_addname(attr);
-		if (attr->xattri_leaf_bp != NULL) {
-			xfs_trans_bhold_release(args->trans,
-						attr->xattri_leaf_bp);
-			attr->xattri_leaf_bp = NULL;
-		}
-
 		return xfs_attr_leaf_addname(attr);
 
 	case XFS_DAS_FOUND_LBLK:
@@ -991,18 +995,31 @@ xfs_attr_leaf_try_add(
 	struct xfs_da_args	*args,
 	struct xfs_buf		*bp)
 {
-	int			retval;
+	int			error;
 
 	/*
-	 * Look up the given attribute in the leaf block.  Figure out if
-	 * the given flags produce an error or call for an atomic rename.
+	 * If the caller provided a buffer to us, it is locked and held in
+	 * the transaction because it just did a shortform to leaf conversion.
+	 * Hence we don't need to read it again. Otherwise read in the leaf
+	 * buffer.
 	 */
-	retval = xfs_attr_leaf_hasname(args, &bp);
-	if (retval != -ENOATTR && retval != -EEXIST)
-		return retval;
-	if (retval == -ENOATTR && (args->attr_flags & XATTR_REPLACE))
+	if (bp) {
+		xfs_trans_bhold_release(args->trans, bp);
+	} else {
+		error = xfs_attr3_leaf_read(args->trans, args->dp, 0, &bp);
+		if (error)
+			return error;
+	}
+
+	/*
+	 * Look up the xattr name to set the insertion point for the new xattr.
+	 */
+	error = xfs_attr3_leaf_lookup_int(bp, args);
+	if (error != -ENOATTR && error != -EEXIST)
 		goto out_brelse;
-	if (retval == -EEXIST) {
+	if (error == -ENOATTR && (args->attr_flags & XATTR_REPLACE))
+		goto out_brelse;
+	if (error == -EEXIST) {
 		if (args->attr_flags & XATTR_CREATE)
 			goto out_brelse;
 
@@ -1022,14 +1039,11 @@ xfs_attr_leaf_try_add(
 		args->rmtvaluelen = 0;
 	}
 
-	/*
-	 * Add the attribute to the leaf block
-	 */
 	return xfs_attr3_leaf_add(bp, args);
 
 out_brelse:
 	xfs_trans_brelse(args->trans, bp);
-	return retval;
+	return error;
 }
 
 /*