xfs: allow setting and clearing of log incompat feature flags

Log incompat feature flags in the superblock exist for one purpose: to
protect the contents of a dirty log from replay on a kernel that isn't
prepared to handle those dirty contents.  This means that they can be
cleared if (a) we know the log is clean and (b) we know that there
aren't any other threads in the system that might be setting or relying
upon a log incompat flag.

Therefore, clear the log incompat flags when we've finished recovering
the log, when we're unmounting cleanly, remounting read-only, or
freezing; and provide a function so that subsequent patches can start
using this.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index ea96b5e45364..1d324c8bac6b 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -3471,6 +3471,22 @@ xlog_recover_finish(
 		 */
 		xfs_log_force(log->l_mp, XFS_LOG_SYNC);
 
+		/*
+		 * Now that we've recovered the log and all the intents, we can
+		 * clear the log incompat feature bits in the superblock
+		 * because there's no longer anything to protect.  We rely on
+		 * the AIL push to write out the updated superblock after
+		 * everything else.
+		 */
+		if (xfs_clear_incompat_log_features(log->l_mp)) {
+			error = xfs_sync_sb(log->l_mp, false);
+			if (error < 0) {
+				xfs_alert(log->l_mp,
+	"Failed to clear log incompat features on recovery");
+				return error;
+			}
+		}
+
 		xlog_recover_process_iunlinks(log);
 
 		xlog_recover_check_summary(log);