[PATCH] xfs: validate sb_logsunit is a multiple of the fs blocksize

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

Make sure the log stripe unit is sane before proceeding with mounting.
AFAICT this means that logsunit has to be 0, 1, or a multiple of the fs
block size.  Found this by setting the LSB of logsunit in xfs/350 and
watching the system crash as soon as we try to write to the log.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_log.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index d729e00..da4dcab 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -659,6 +659,12 @@ xfs_log_mount(
 			 XFS_FSB_TO_B(mp, mp->m_sb.sb_logblocks),
 			 XFS_MAX_LOG_BYTES);
 		error = -EINVAL;
+	} else if (mp->m_sb.sb_logsunit > 1 &&
+		   mp->m_sb.sb_logsunit % mp->m_sb.sb_blocksize) {
+		xfs_warn(mp,
+		"log stripe unit %u bytes must be a multiple of block size",
+			 mp->m_sb.sb_logsunit);
+		error = -EINVAL;
 	}
 	if (error) {
 		if (xfs_sb_version_hascrc(&mp->m_sb)) {