[PATCH 2/2] xfsprogs: Add error injection to allocate only single block sized extents for files

[Chandan Babu R <chandanrlinux@gmail.com>]

This commit adds XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT error tag which
enables inject command to limit space allocation for files to single
block sized extents.

One way to use this error tag is to,
1. Consume all of the free space by sequentially writing to a file.
2. Punch alternate blocks of the file. This causes CNTBT to contain
   sufficient number of one block sized extent records.
3. Inject XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT error tag.

After step 3, space allocation requests issued by XFS kernel module for
files will be limited to single block sized extents only.

ENOSPC error code is returned to userspace when there aren't any "single
block sized" free extents left in the filesystem.

Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
---
 io/inject.c           | 1 +
 libxfs/xfs_errortag.h | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/io/inject.c b/io/inject.c
index 9e3d5ad4..9a401a1e 100644
--- a/io/inject.c
+++ b/io/inject.c
@@ -56,6 +56,7 @@ error_tag(char *name)
 		{ XFS_ERRTAG_IUNLINK_FALLBACK,		"iunlink_fallback" },
 		{ XFS_ERRTAG_BUF_IOERROR,		"buf_ioerror" },
 		{ XFS_ERRTAG_REDUCE_MAX_IEXTENTS,	"reduce_max_iextents" },
+		{ XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT,	"bmap_alloc_minlen_extent" },
 		{ XFS_ERRTAG_MAX,			NULL }
 	};
 	int	count;
diff --git a/libxfs/xfs_errortag.h b/libxfs/xfs_errortag.h
index 1c56fcce..6ca9084b 100644
--- a/libxfs/xfs_errortag.h
+++ b/libxfs/xfs_errortag.h
@@ -57,7 +57,8 @@
 #define XFS_ERRTAG_IUNLINK_FALLBACK			34
 #define XFS_ERRTAG_BUF_IOERROR				35
 #define XFS_ERRTAG_REDUCE_MAX_IEXTENTS			36
-#define XFS_ERRTAG_MAX					37
+#define XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT		37
+#define XFS_ERRTAG_MAX					38
 
 /*
  * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.
@@ -99,5 +100,6 @@
 #define XFS_RANDOM_IUNLINK_FALLBACK			(XFS_RANDOM_DEFAULT/10)
 #define XFS_RANDOM_BUF_IOERROR				XFS_RANDOM_DEFAULT
 #define XFS_RANDOM_REDUCE_MAX_IEXTENTS			1
+#define XFS_RANDOM_BMAP_ALLOC_MINLEN_EXTENT		1
 
 #endif /* __XFS_ERRORTAG_H_ */
-- 
2.28.0