xfs: random buffer write failure errortag

Introduce an error tag to randomly fail async buffer writes. This is
primarily to facilitate testing of the XFS error configuration
mechanism.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_errortag.h

@@ -55,7 +55,8 @@
 #define XFS_ERRTAG_FORCE_SCRUB_REPAIR			32
 #define XFS_ERRTAG_FORCE_SUMMARY_RECALC			33
 #define XFS_ERRTAG_IUNLINK_FALLBACK			34
-#define XFS_ERRTAG_MAX					35
+#define XFS_ERRTAG_BUF_IOERROR				35
+#define XFS_ERRTAG_MAX					36
 
 /*
  * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.
@@ -95,5 +96,6 @@
 #define XFS_RANDOM_FORCE_SCRUB_REPAIR			1
 #define XFS_RANDOM_FORCE_SUMMARY_RECALC			1
 #define XFS_RANDOM_IUNLINK_FALLBACK			(XFS_RANDOM_DEFAULT/10)
+#define XFS_RANDOM_BUF_IOERROR				XFS_RANDOM_DEFAULT
 
 #endif /* __XFS_ERRORTAG_H_ */

fs/xfs/xfs_buf.c

@@ -1289,6 +1289,12 @@ xfs_buf_bio_end_io(
 	struct bio		*bio)
 {
 	struct xfs_buf		*bp = (struct xfs_buf *)bio->bi_private;
+	struct xfs_mount	*mp = bp->b_mount;
+
+	if (!bio->bi_status &&
+	    (bp->b_flags & XBF_WRITE) && (bp->b_flags & XBF_ASYNC) &&
+	    XFS_TEST_ERROR(false, mp, XFS_ERRTAG_BUF_IOERROR))
+		bio->bi_status = BLK_STS_IOERR;
 
 	/*
 	 * don't overwrite existing errors - otherwise we can lose errors on

fs/xfs/xfs_error.c

@@ -53,6 +53,7 @@ static unsigned int xfs_errortag_random_default[] = {
 	XFS_RANDOM_FORCE_SCRUB_REPAIR,
 	XFS_RANDOM_FORCE_SUMMARY_RECALC,
 	XFS_RANDOM_IUNLINK_FALLBACK,
+	XFS_RANDOM_BUF_IOERROR,
 };
 
 struct xfs_errortag_attr {
@@ -162,6 +163,7 @@ XFS_ERRORTAG_ATTR_RW(buf_lru_ref,	XFS_ERRTAG_BUF_LRU_REF);
 XFS_ERRORTAG_ATTR_RW(force_repair,	XFS_ERRTAG_FORCE_SCRUB_REPAIR);
 XFS_ERRORTAG_ATTR_RW(bad_summary,	XFS_ERRTAG_FORCE_SUMMARY_RECALC);
 XFS_ERRORTAG_ATTR_RW(iunlink_fallback,	XFS_ERRTAG_IUNLINK_FALLBACK);
+XFS_ERRORTAG_ATTR_RW(buf_ioerror,	XFS_ERRTAG_BUF_IOERROR);
 
 static struct attribute *xfs_errortag_attrs[] = {
 	XFS_ERRORTAG_ATTR_LIST(noerror),
@@ -199,6 +201,7 @@ static struct attribute *xfs_errortag_attrs[] = {
 	XFS_ERRORTAG_ATTR_LIST(force_repair),
 	XFS_ERRORTAG_ATTR_LIST(bad_summary),
 	XFS_ERRORTAG_ATTR_LIST(iunlink_fallback),
+	XFS_ERRORTAG_ATTR_LIST(buf_ioerror),
 	NULL,
 };