[PATCH v6 7/7] xfs: add error injection for per-AG resv failure when shrinkfs

[Gao Xiang <hsiangkao@xxxxxxxxxx>]

per-AG resv failure after fixing up freespace is hard to test in an
effective way, so directly add an error injection path to observe
such error handling path works as expected.

Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
---
 fs/xfs/libxfs/xfs_ag.c       | 5 +++++
 fs/xfs/libxfs/xfs_errortag.h | 4 +++-
 fs/xfs/xfs_error.c           | 2 ++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
index c6e68e265269..5076913c153f 100644
--- a/fs/xfs/libxfs/xfs_ag.c
+++ b/fs/xfs/libxfs/xfs_ag.c
@@ -23,6 +23,7 @@
 #include "xfs_ag_resv.h"
 #include "xfs_health.h"
 #include "xfs_error.h"
+#include "xfs_errortag.h"
 #include "xfs_bmap.h"
 #include "xfs_defer.h"
 #include "xfs_log_format.h"
@@ -559,6 +560,10 @@ xfs_ag_shrink_space(
 	be32_add_cpu(&agf->agf_length, -len);
 
 	err2 = xfs_ag_resv_init(agibp->b_pag, *tpp);
+
+	if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_SHRINKFS_AG_RESV_FAIL))
+		err2 = -ENOSPC;
+
 	if (err2) {
 		be32_add_cpu(&agi->agi_length, len);
 		be32_add_cpu(&agf->agf_length, len);
diff --git a/fs/xfs/libxfs/xfs_errortag.h b/fs/xfs/libxfs/xfs_errortag.h
index 6ca9084b6934..5fd71a930b68 100644
--- a/fs/xfs/libxfs/xfs_errortag.h
+++ b/fs/xfs/libxfs/xfs_errortag.h
@@ -40,6 +40,7 @@
 #define XFS_ERRTAG_REFCOUNT_FINISH_ONE			25
 #define XFS_ERRTAG_BMAP_FINISH_ONE			26
 #define XFS_ERRTAG_AG_RESV_CRITICAL			27
+
 /*
  * DEBUG mode instrumentation to test and/or trigger delayed allocation
  * block killing in the event of failed writes. When enabled, all
@@ -58,7 +59,8 @@
 #define XFS_ERRTAG_BUF_IOERROR				35
 #define XFS_ERRTAG_REDUCE_MAX_IEXTENTS			36
 #define XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT		37
-#define XFS_ERRTAG_MAX					38
+#define XFS_ERRTAG_SHRINKFS_AG_RESV_FAIL		38
+#define XFS_ERRTAG_MAX					39
 
 /*
  * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.
diff --git a/fs/xfs/xfs_error.c b/fs/xfs/xfs_error.c
index 185b4915b7bf..7bae34bfddd2 100644
--- a/fs/xfs/xfs_error.c
+++ b/fs/xfs/xfs_error.c
@@ -168,6 +168,7 @@ XFS_ERRORTAG_ATTR_RW(iunlink_fallback,	XFS_ERRTAG_IUNLINK_FALLBACK);
 XFS_ERRORTAG_ATTR_RW(buf_ioerror,	XFS_ERRTAG_BUF_IOERROR);
 XFS_ERRORTAG_ATTR_RW(reduce_max_iextents,	XFS_ERRTAG_REDUCE_MAX_IEXTENTS);
 XFS_ERRORTAG_ATTR_RW(bmap_alloc_minlen_extent,	XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT);
+XFS_ERRORTAG_ATTR_RW(shrinkfs_ag_resv_fail, XFS_ERRTAG_SHRINKFS_AG_RESV_FAIL);
 
 static struct attribute *xfs_errortag_attrs[] = {
 	XFS_ERRORTAG_ATTR_LIST(noerror),
@@ -208,6 +209,7 @@ static struct attribute *xfs_errortag_attrs[] = {
 	XFS_ERRORTAG_ATTR_LIST(buf_ioerror),
 	XFS_ERRORTAG_ATTR_LIST(reduce_max_iextents),
 	XFS_ERRORTAG_ATTR_LIST(bmap_alloc_minlen_extent),
+	XFS_ERRORTAG_ATTR_LIST(shrinkfs_ag_resv_fail),
 	NULL,
 };
 
-- 
2.27.0