[PATCH v2] mkfs.xfs: fix ASSERT on too-small device with stripe geometry

[Pavel Reichl <preichl@redhat.com>]

When a too-small device is created with stripe geometry, we hit an
assert in align_ag_geometry():

mkfs.xfs: xfs_mkfs.c:2834: align_ag_geometry: Assertion `cfg->agcount != 0' failed.

This is because align_ag_geometry() finds that the size of the last
(only) AG is too small, and attempts to trim it off.  Obviously 0
AGs is invalid, and we hit the ASSERT.

Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Suggested-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Pavel Reichl <preichl@redhat.com>
---
 include/xfs_multidisk.h | 14 +++++++-------
 mkfs/xfs_mkfs.c         |  6 +++---
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/xfs_multidisk.h b/include/xfs_multidisk.h
index 1b9936ec..abfb50ce 100644
--- a/include/xfs_multidisk.h
+++ b/include/xfs_multidisk.h
@@ -14,7 +14,6 @@
 #define	XFS_DFL_BLOCKSIZE_LOG	12		/* 4096 byte blocks */
 #define	XFS_DINODE_DFL_LOG	8		/* 256 byte inodes */
 #define	XFS_DINODE_DFL_CRC_LOG	9		/* 512 byte inodes for CRCs */
-#define	XFS_MIN_DATA_BLOCKS	100
 #define	XFS_MIN_INODE_PERBLOCK	2		/* min inodes per block */
 #define	XFS_DFL_IMAXIMUM_PCT	25		/* max % of space for inodes */
 #define	XFS_MIN_REC_DIRSIZE	12		/* 4096 byte dirblocks (V2) */
@@ -25,13 +24,14 @@
 						 * accept w/o warnings
 						 */
 
-#define XFS_AG_BYTES(bblog)	((long long)BBSIZE << (bblog))
-#define	XFS_AG_MIN_BYTES	((XFS_AG_BYTES(15)))	/* 16 MB */
-#define	XFS_AG_MAX_BYTES	((XFS_AG_BYTES(31)))	/* 1 TB */
-#define XFS_AG_MIN_BLOCKS(blog)	(XFS_AG_MIN_BYTES >> (blog))
-#define XFS_AG_MAX_BLOCKS(blog)	((XFS_AG_MAX_BYTES - 1) >> (blog))
+#define XFS_AG_BYTES(bblog)		((long long)BBSIZE << (bblog))
+#define	XFS_MIN_DATA_BLOCKS(cfg)	(XFS_AG_MIN_BLOCKS((cfg)->blocklog))
+#define	XFS_AG_MIN_BYTES		((XFS_AG_BYTES(15)))	/* 16 MB */
+#define	XFS_AG_MAX_BYTES		((XFS_AG_BYTES(31)))	/* 1 TB */
+#define XFS_AG_MIN_BLOCKS(blog)		(XFS_AG_MIN_BYTES >> (blog))
+#define XFS_AG_MAX_BLOCKS(blog)		((XFS_AG_MAX_BYTES - 1) >> (blog))
 
-#define XFS_MAX_AGNUMBER	((xfs_agnumber_t)(NULLAGNUMBER - 1))
+#define XFS_MAX_AGNUMBER		((xfs_agnumber_t)(NULLAGNUMBER - 1))
 
 /*
  * These values define what we consider a "multi-disk" filesystem. That is, a
diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index a687f385..204dfff1 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -2530,10 +2530,10 @@ _("size %s specified for data subvolume is too large, maximum is %lld blocks\n")
 		cfg->dblocks = DTOBT(xi->dsize, cfg->blocklog);
 	}
 
-	if (cfg->dblocks < XFS_MIN_DATA_BLOCKS) {
+	if (cfg->dblocks < XFS_MIN_DATA_BLOCKS(cfg)) {
 		fprintf(stderr,
-_("size %lld of data subvolume is too small, minimum %d blocks\n"),
-			(long long)cfg->dblocks, XFS_MIN_DATA_BLOCKS);
+_("size %lld of data subvolume is too small, minimum %lld blocks\n"),
+			(long long)cfg->dblocks, XFS_MIN_DATA_BLOCKS(cfg));
 		usage();
 	}
 
-- 
2.26.2