[PATCH 6/4] mkfs: round log size down if rounding log start up causes overflow

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

If rounding the log start up to the next stripe unit would cause the log
to overrun the end of the AG, round the log size down by a stripe unit.
We already ensured that logblocks was small enough to fit inside the AG,
so the minor adjustment should suffice.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 mkfs/xfs_mkfs.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index b932acaa..cfa38f17 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -3219,9 +3219,19 @@ align_internal_log(
 	int			max_logblocks)
 {
 	/* round up log start if necessary */
-	if ((cfg->logstart % sunit) != 0)
+	if ((cfg->logstart % sunit) != 0) {
 		cfg->logstart = ((cfg->logstart + (sunit - 1)) / sunit) * sunit;
 
+		/*
+		 * If rounding up logstart to a stripe boundary moves the end
+		 * of the log past the end of the AG, reduce logblocks to get
+		 * it back under EOAG.
+		 */
+		if (!libxfs_verify_fsbext(mp, cfg->logstart, cfg->logblocks) &&
+		    cfg->logblocks > sunit)
+			cfg->logblocks -= sunit;
+	}
+
 	/* If our log start overlaps the next AG's metadata, fail. */
 	if (!libxfs_verify_fsbno(mp, cfg->logstart)) {
 		fprintf(stderr,