xfs: remote xattr removal in xfs_attr_set_iter() is conditional

We may not have a remote value for the old xattr we have to remove,
so skip over the remote value removal states and go straight to
the xattr name removal in the leaf/node block.
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

@@ -494,15 +494,14 @@ xfs_attr_set_iter(
 		/*
 		 * We must "flip" the incomplete flags on the "new" and "old"
 		 * attribute/value pairs so that one disappears and one appears
-		 * atomically.  Then we must remove the "old" attribute/value
-		 * pair.
+		 * atomically.
 		 */
 		error = xfs_attr3_leaf_flipflags(args);
 		if (error)
 			return error;
 		/*
-		 * Commit the flag value change and start the next trans
-		 * in series at REMOVE_OLD.
+		 * We must commit the flag value change now to make it atomic
+		 * and then we can start the next trans in series at REMOVE_OLD.
 		 */
 		error = -EAGAIN;
 		attr->xattri_dela_state++;
@@ -511,41 +510,43 @@ xfs_attr_set_iter(
 	case XFS_DAS_LEAF_REMOVE_OLD:
 	case XFS_DAS_NODE_REMOVE_OLD:
 		/*
-		 * Dismantle the "old" attribute/value pair by removing a
-		 * "remote" value (if it exists).
+		 * If we have a remote attr, start the process of removing it
+		 * by invalidating any cached buffers.
+		 *
+		 * If we don't have a remote attr, we skip the remote block
+		 * removal state altogether with a second state increment.
 		 */
 		xfs_attr_restore_rmt_blk(args);
+		if (args->rmtblkno) {
 			error = xfs_attr_rmtval_invalidate(args);
 			if (error)
 				return error;
+		} else {
+			attr->xattri_dela_state++;
+		}
 
 		attr->xattri_dela_state++;
-		fallthrough;
-	case XFS_DAS_RM_LBLK:
-	case XFS_DAS_RM_NBLK:
-		if (args->rmtblkno) {
+		goto next_state;
+
+	case XFS_DAS_LEAF_REMOVE_RMT:
+	case XFS_DAS_NODE_REMOVE_RMT:
 		error = xfs_attr_rmtval_remove(attr);
 		if (error == -EAGAIN)
-				trace_xfs_attr_set_iter_return(
-					attr->xattri_dela_state, args->dp);
+			break;
 		if (error)
 			return error;
 
-			attr->xattri_dela_state = XFS_DAS_RD_LEAF;
-			trace_xfs_attr_set_iter_return(attr->xattri_dela_state,
-						       args->dp);
-			return -EAGAIN;
-		}
-
 		/*
-		 * This is the end of the shared leaf/node sequence. We need
-		 * to continue at the next state in the sequence, but we can't
-		 * easily just fall through. So we increment to the next state
-		 * and then jump back to switch statement to evaluate the next
-		 * state correctly.
+		 * We've finished removing the remote attr blocks, so commit the
+		 * transaction and move on to removing the attr name from the
+		 * leaf/node block. Removing the attr might require a full
+		 * transaction reservation for btree block freeing, so we
+		 * can't do that in the same transaction where we removed the
+		 * remote attr blocks.
 		 */
+		error = -EAGAIN;
 		attr->xattri_dela_state++;
-		goto next_state;
+		break;
 
 	case XFS_DAS_RD_LEAF:
 		/*

fs/xfs/libxfs/xfs_attr.h

@@ -456,7 +456,7 @@ enum xfs_delattr_state {
 	XFS_DAS_LEAF_ALLOC_RMT,		/* We are allocating remote blocks */
 	XFS_DAS_LEAF_REPLACE,		/* Perform replace ops on a leaf */
 	XFS_DAS_LEAF_REMOVE_OLD,	/* Start removing old attr from leaf */
-	XFS_DAS_RM_LBLK,		/* A rename is removing leaf blocks */
+	XFS_DAS_LEAF_REMOVE_RMT,	/* A rename is removing remote blocks */
 	XFS_DAS_RD_LEAF,		/* Read in the new leaf */
 
 	/* Node state set sequence, must match leaf state above */
@@ -464,7 +464,7 @@ enum xfs_delattr_state {
 	XFS_DAS_NODE_ALLOC_RMT,		/* We are allocating remote blocks */
 	XFS_DAS_NODE_REPLACE,		/* Perform replace ops on a node */
 	XFS_DAS_NODE_REMOVE_OLD,	/* Start removing old attr from node */
-	XFS_DAS_RM_NBLK,		/* A rename is removing node blocks */
+	XFS_DAS_NODE_REMOVE_RMT,	/* A rename is removing remote blocks */
 	XFS_DAS_CLR_FLAG,		/* Clear incomplete flag */
 
 	XFS_DAS_DONE,			/* finished operation */
@@ -482,13 +482,13 @@ enum xfs_delattr_state {
 	{ XFS_DAS_LEAF_ALLOC_RMT,	"XFS_DAS_LEAF_ALLOC_RMT" }, \
 	{ XFS_DAS_LEAF_REPLACE,		"XFS_DAS_LEAF_REPLACE" }, \
 	{ XFS_DAS_LEAF_REMOVE_OLD,	"XFS_DAS_LEAF_REMOVE_OLD" }, \
-	{ XFS_DAS_RM_LBLK,		"XFS_DAS_RM_LBLK" }, \
+	{ XFS_DAS_LEAF_REMOVE_RMT,	"XFS_DAS_LEAF_REMOVE_RMT" }, \
 	{ XFS_DAS_RD_LEAF,		"XFS_DAS_RD_LEAF" }, \
 	{ XFS_DAS_NODE_SET_RMT,		"XFS_DAS_NODE_SET_RMT" }, \
 	{ XFS_DAS_NODE_ALLOC_RMT,	"XFS_DAS_NODE_ALLOC_RMT" },  \
 	{ XFS_DAS_NODE_REPLACE,		"XFS_DAS_NODE_REPLACE" },  \
 	{ XFS_DAS_NODE_REMOVE_OLD,	"XFS_DAS_NODE_REMOVE_OLD" }, \
-	{ XFS_DAS_RM_NBLK,		"XFS_DAS_RM_NBLK" }, \
+	{ XFS_DAS_NODE_REMOVE_RMT,	"XFS_DAS_NODE_REMOVE_RMT" }, \
 	{ XFS_DAS_CLR_FLAG,		"XFS_DAS_CLR_FLAG" }, \
 	{ XFS_DAS_DONE,			"XFS_DAS_DONE" }
 

fs/xfs/xfs_trace.h

@@ -4140,13 +4140,13 @@ TRACE_DEFINE_ENUM(XFS_DAS_LEAF_SET_RMT);
 TRACE_DEFINE_ENUM(XFS_DAS_LEAF_ALLOC_RMT);
 TRACE_DEFINE_ENUM(XFS_DAS_LEAF_REPLACE);
 TRACE_DEFINE_ENUM(XFS_DAS_LEAF_REMOVE_OLD);
-TRACE_DEFINE_ENUM(XFS_DAS_RM_LBLK);
+TRACE_DEFINE_ENUM(XFS_DAS_LEAF_REMOVE_RMT);
 TRACE_DEFINE_ENUM(XFS_DAS_RD_LEAF);
 TRACE_DEFINE_ENUM(XFS_DAS_NODE_SET_RMT);
 TRACE_DEFINE_ENUM(XFS_DAS_NODE_ALLOC_RMT);
 TRACE_DEFINE_ENUM(XFS_DAS_NODE_REPLACE);
 TRACE_DEFINE_ENUM(XFS_DAS_NODE_REMOVE_OLD);
-TRACE_DEFINE_ENUM(XFS_DAS_RM_NBLK);
+TRACE_DEFINE_ENUM(XFS_DAS_NODE_REMOVE_RMT);
 TRACE_DEFINE_ENUM(XFS_DAS_CLR_FLAG);
 
 DECLARE_EVENT_CLASS(xfs_das_state_class,