xfs: simulate per-AG reservations being critically low

Create an error injection point that enables us to simulate being
critically low on per-AG block reservations.  This should enable us to
simulate this specific ENOSPC condition so that we can test falling back
to a regular file copy.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

2 files changed, 6 insertions, 2 deletions

diff --git a/fs/xfs/libxfs/xfs_ag_resv.c b/fs/xfs/libxfs/xfs_ag_resv.c
index adf770f0d011..e5ebc3770460 100644
--- a/fs/xfs/libxfs/xfs_ag_resv.c
+++ b/fs/xfs/libxfs/xfs_ag_resv.c
@@ -109,7 +109,9 @@ xfs_ag_resv_critical(
         trace_xfs_ag_resv_critical(pag, type, avail);
 
         /* Critically low if less than 10% or max btree height remains. */
-        return avail < orig / 10 || avail < XFS_BTREE_MAXLEVELS;
+        return XFS_TEST_ERROR(avail < orig / 10 || avail < XFS_BTREE_MAXLEVELS,
+                        pag->pag_mount, XFS_ERRTAG_AG_RESV_CRITICAL,
+                        XFS_RANDOM_AG_RESV_CRITICAL);
 }
 
 /*
diff --git a/fs/xfs/xfs_error.h b/fs/xfs/xfs_error.h
index 8d8e1b07d295..05f8666733a0 100644
--- a/fs/xfs/xfs_error.h
+++ b/fs/xfs/xfs_error.h
@@ -95,7 +95,8 @@ extern void xfs_verifier_error(struct xfs_buf *bp);
 #define XFS_ERRTAG_REFCOUNT_CONTINUE_UPDATE             24
 #define XFS_ERRTAG_REFCOUNT_FINISH_ONE                  25
 #define XFS_ERRTAG_BMAP_FINISH_ONE                      26
-#define XFS_ERRTAG_MAX                                  27
+#define XFS_ERRTAG_AG_RESV_CRITICAL                     27
+#define XFS_ERRTAG_MAX                                  28
 
 /*
  * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.
@@ -127,6 +128,7 @@ extern void xfs_verifier_error(struct xfs_buf *bp);
 #define XFS_RANDOM_REFCOUNT_CONTINUE_UPDATE             1
 #define XFS_RANDOM_REFCOUNT_FINISH_ONE                  1
 #define XFS_RANDOM_BMAP_FINISH_ONE                      1
+#define XFS_RANDOM_AG_RESV_CRITICAL                     4
 
 #ifdef DEBUG
 extern int xfs_error_test_active;