1 files changed, 16 insertions, 3 deletions

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 7f4f9370d0e7..4dad756962d0 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -2387,14 +2387,27 @@ xlog_state_do_callback(
 
 
                                 /*
-                                 * update the last_sync_lsn before we drop the
+                                 * Completion of a iclog IO does not imply that
+                                 * a transaction has completed, as transactions
+                                 * can be large enough to span many iclogs. We
+                                 * cannot change the tail of the log half way
+                                 * through a transaction as this may be the only
+                                 * transaction in the log and moving th etail to
+                                 * point to the middle of it will prevent
+                                 * recovery from finding the start of the
+                                 * transaction. Hence we should only update the
+                                 * last_sync_lsn if this iclog contains
+                                 * transaction completion callbacks on it.
+                                 *
+                                 * We have to do this before we drop the
                                  * icloglock to ensure we are the only one that
                                  * can update it.
                                  */
                                 ASSERT(XFS_LSN_CMP(atomic64_read(&log->l_last_sync_lsn),
                                         be64_to_cpu(iclog->ic_header.h_lsn)) <= 0);
-                                atomic64_set(&log->l_last_sync_lsn,
-                                        be64_to_cpu(iclog->ic_header.h_lsn));
+                                if (iclog->ic_callback)
+                                        atomic64_set(&log->l_last_sync_lsn,
+                                                be64_to_cpu(iclog->ic_header.h_lsn));
 
                         } else
                                 ioerrors++;