xfs: make attr lookup returns consistent

Shortform, leaf and remote value attr value retrieval return
different values for success. This makes it more complex to handle
actual errors xfs_attr_get() as some errors mean success and some
mean failure. Make the return values consistent for success and
failure consistent for all attribute formats.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_attr.c

@@ -97,7 +97,10 @@ xfs_inode_hasattr(
  * Overall external interface routines.
  *========================================================================*/
 
-/* Retrieve an extended attribute and its value.  Must have ilock. */
+/*
+ * Retrieve an extended attribute and its value.  Must have ilock.
+ * Returns 0 on successful retrieval, otherwise an error.
+ */
 int
 xfs_attr_get_ilocked(
 	struct xfs_inode	*ip,
@@ -147,7 +150,7 @@ xfs_attr_get(
 	xfs_iunlock(ip, lock_mode);
 
 	*valuelenp = args.valuelen;
-	return error == -EEXIST ? 0 : error;
+	return error;
 }
 
 /*
@@ -768,6 +771,8 @@ xfs_attr_leaf_removename(
  *
  * This leaf block cannot have a "remote" value, we only call this routine
  * if bmap_one_block() says there is only one block (ie: no remote blks).
+ *
+ * Returns 0 on successful retrieval, otherwise an error.
  */
 STATIC int
 xfs_attr_leaf_get(xfs_da_args_t *args)
@@ -789,10 +794,15 @@ xfs_attr_leaf_get(xfs_da_args_t *args)
 	}
 	error = xfs_attr3_leaf_getvalue(bp, args);
 	xfs_trans_brelse(args->trans, bp);
-	if (!error && (args->rmtblkno > 0) && !(args->flags & ATTR_KERNOVAL)) {
-		error = xfs_attr_rmtval_get(args);
-	}
+	if (error)
 		return error;
+
+	/* check if we have to retrieve a remote attribute to get the value */
+	if (args->flags & ATTR_KERNOVAL)
+		return 0;
+	if (!args->rmtblkno)
+		return 0;
+	return xfs_attr_rmtval_get(args);
 }
 
 /*========================================================================
@@ -1268,11 +1278,13 @@ xfs_attr_refillstate(xfs_da_state_t *state)
 }
 
 /*
- * Look up a filename in a node attribute list.
+ * Retrieve the attribute data from a node attribute list.
  *
  * This routine gets called for any attribute fork that has more than one
  * block, ie: both true Btree attr lists and for single-leaf-blocks with
  * "remote" values taking up more blocks.
+ *
+ * Returns 0 on successful retrieval, otherwise an error.
  */
 STATIC int
 xfs_attr_node_get(xfs_da_args_t *args)
@@ -1294,24 +1306,27 @@ xfs_attr_node_get(xfs_da_args_t *args)
 	error = xfs_da3_node_lookup_int(state, &retval);
 	if (error) {
 		retval = error;
-	} else if (retval == -EEXIST) {
-		blk = &state->path.blk[ state->path.active-1 ];
-		ASSERT(blk->bp != NULL);
-		ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
+		goto out_release;
+	}
+	if (retval != -EEXIST)
+		goto out_release;
 
 	/*
 	 * Get the value, local or "remote"
 	 */
+	blk = &state->path.blk[state->path.active - 1];
 	retval = xfs_attr3_leaf_getvalue(blk->bp, args);
-		if (!retval && (args->rmtblkno > 0)
-		    && !(args->flags & ATTR_KERNOVAL)) {
+	if (retval)
+		goto out_release;
+	if (args->flags & ATTR_KERNOVAL)
+		goto out_release;
+	if (args->rmtblkno > 0)
 		retval = xfs_attr_rmtval_get(args);
-		}
-	}
 
 	/*
 	 * If not in a transaction, we have to release all the buffers.
 	 */
+out_release:
 	for (i = 0; i < state->path.active; i++) {
 		xfs_trans_brelse(args->trans, state->path.blk[i].bp);
 		state->path.blk[i].bp = NULL;

fs/xfs/libxfs/xfs_attr_leaf.c

@@ -720,9 +720,12 @@ xfs_attr_shortform_lookup(xfs_da_args_t *args)
 }
 
 /*
- * Look up a name in a shortform attribute list structure.
+ * Retreive the attribute value and length.
+ *
+ * If ATTR_KERNOVAL is specified, only the length needs to be returned.
+ * Unlike a lookup, we only return an error if the attribute does not
+ * exist or we can't retrieve the value.
  */
-/*ARGSUSED*/
 int
 xfs_attr_shortform_getvalue(xfs_da_args_t *args)
 {
@@ -743,7 +746,7 @@ xfs_attr_shortform_getvalue(xfs_da_args_t *args)
 			continue;
 		if (args->flags & ATTR_KERNOVAL) {
 			args->valuelen = sfe->valuelen;
-			return -EEXIST;
+			return 0;
 		}
 		if (args->valuelen < sfe->valuelen) {
 			args->valuelen = sfe->valuelen;
@@ -752,7 +755,7 @@ xfs_attr_shortform_getvalue(xfs_da_args_t *args)
 		args->valuelen = sfe->valuelen;
 		memcpy(args->value, &sfe->nameval[args->namelen],
 						    args->valuelen);
-		return -EEXIST;
+		return 0;
 	}
 	return -ENOATTR;
 }
@@ -2350,6 +2353,10 @@ xfs_attr3_leaf_lookup_int(
 /*
  * Get the value associated with an attribute name from a leaf attribute
  * list structure.
+ *
+ * If ATTR_KERNOVAL is specified, only the length needs to be returned.
+ * Unlike a lookup, we only return an error if the attribute does not
+ * exist or we can't retrieve the value.
  */
 int
 xfs_attr3_leaf_getvalue(

fs/xfs/libxfs/xfs_attr_remote.c

@@ -358,6 +358,8 @@ xfs_attr_rmtval_copyin(
 /*
  * Read the value associated with an attribute from the out-of-line buffer
  * that we stored it in.
+ *
+ * Returns 0 on successful retrieval, otherwise an error.
  */
 int
 xfs_attr_rmtval_get(

fs/xfs/scrub/attr.c

@@ -163,8 +163,6 @@ xchk_xattr_listent(
 	args.valuelen = valuelen;
 
 	error = xfs_attr_get_ilocked(context->dp, &args);
-	if (error == -EEXIST)
-		error = 0;
 	if (!xchk_fblock_process_error(sx->sc, XFS_ATTR_FORK, args.blkno,
 			&error))
 		goto fail_xref;