[PATCH 4/6] mkfs: validate start and end of aligned logs

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

Validate that the start and end of the log stay within a single AG if
we adjust either end to align to stripe units.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 mkfs/xfs_mkfs.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)


diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index ddb25ecc..468b8fde 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -3033,15 +3033,28 @@ align_internal_log(
 	struct xfs_mount	*mp,
 	int			sunit)
 {
+	uint64_t		logend;
+
 	/* round up log start if necessary */
 	if ((cfg->logstart % sunit) != 0)
 		cfg->logstart = ((cfg->logstart + (sunit - 1)) / sunit) * sunit;
 
+	/* If our log start overlaps the next AG's metadata, fail. */
+	if (!xfs_verify_fsbno(mp, cfg->logstart)) {
+			fprintf(stderr,
+_("Due to stripe alignment, the internal log start (%lld) cannot be aligned\n"
+  "within an allocation group.\n"),
+			(long long) cfg->logstart);
+		usage();
+	}
+
 	/* round up/down the log size now */
 	align_log_size(cfg, sunit);
 
 	/* check the aligned log still fits in an AG. */
-	if (cfg->logblocks > cfg->agsize - XFS_FSB_TO_AGBNO(mp, cfg->logstart)) {
+	logend = cfg->logstart + cfg->logblocks - 1;
+	if (XFS_FSB_TO_AGNO(mp, cfg->logstart) != XFS_FSB_TO_AGNO(mp, logend) ||
+	    !xfs_verify_fsbno(mp, logend)) {
 		fprintf(stderr,
 _("Due to stripe alignment, the internal log size (%lld) is too large.\n"
   "Must fit within an allocation group.\n"),