[PATCH] xfs: prohibit fstrim in norecovery mode

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

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

The xfs fstrim implementation uses the free space btrees to find free
space that can be discarded.  If we haven't recovered the log, the bnobt
will be stale and we absolutely *cannot* use stale metadata to zap the
underlying storage.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_discard.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c
index 93f07edafd81..9ee2a7d02e70 100644
--- a/fs/xfs/xfs_discard.c
+++ b/fs/xfs/xfs_discard.c
@@ -161,6 +161,14 @@ xfs_ioc_trim(
 		return -EPERM;
 	if (!blk_queue_discard(q))
 		return -EOPNOTSUPP;
+
+	/*
+	 * We haven't recovered the log, so we cannot use our bnobt-guided
+	 * storage zapping commands.
+	 */
+	if (mp->m_flags & XFS_MOUNT_NORECOVERY)
+		return -EROFS;
+
 	if (copy_from_user(&range, urange, sizeof(range)))
 		return -EFAULT;