[PATCH 1/4] xfs_repair: ignore empty xattr leaf blocks

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

As detailed in the previous commit, empty xattr leaf blocks can be the
benign byproduct of the system going down during the multi-step process
of adding a large xattr to a file that has no xattrs.  If we find one at
attr fork offset 0, we should clear it, but this isn't a corruption.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 repair/attr_repair.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)


diff --git a/repair/attr_repair.c b/repair/attr_repair.c
index 2055d96e..c3a6d502 100644
--- a/repair/attr_repair.c
+++ b/repair/attr_repair.c
@@ -579,6 +579,26 @@ process_leaf_attr_block(
 	firstb = mp->m_sb.sb_blocksize;
 	stop = xfs_attr3_leaf_hdr_size(leaf);
 
+	/*
+	 * Empty leaf blocks at offset zero can occur as a race between
+	 * setxattr and the system going down, so we only take action if we're
+	 * running in modify mode.  See xfs_attr3_leaf_verify for details of
+	 * how we've screwed this up many times.
+	 */
+	if (!leafhdr.count && da_bno == 0) {
+		if (no_modify) {
+			do_log(
+	_("would clear empty leaf attr block 0, inode %" PRIu64 "\n"),
+					ino);
+			return 0;
+		}
+
+		do_warn(
+	_("will clear empty leaf attr block 0, inode %" PRIu64 "\n"),
+				ino);
+		return 1;
+	}
+
 	/* does the count look sorta valid? */
 	if (!leafhdr.count ||
 	    leafhdr.count * sizeof(xfs_attr_leaf_entry_t) + stop >