JFS: Take logsync lock before testing mp->lsn

This fixes a race where lsn could be cleared before taking the lock

Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>

1 files changed, 2 insertions, 5 deletions

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 4fb3ed184925..c161c98954e0 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -532,10 +532,10 @@ dbUpdatePMap(struct inode *ipbmap,
 
                 lastlblkno = lblkno;
 
+                LOGSYNC_LOCK(log, flags);
                 if (mp->lsn != 0) {
                         /* inherit older/smaller lsn */
                         logdiff(diffp, mp->lsn, log);
-                        LOGSYNC_LOCK(log, flags);
                         if (difft < diffp) {
                                 mp->lsn = lsn;
 
@@ -548,20 +548,17 @@ dbUpdatePMap(struct inode *ipbmap,
                         logdiff(diffp, mp->clsn, log);
                         if (difft > diffp)
                                 mp->clsn = tblk->clsn;
-                        LOGSYNC_UNLOCK(log, flags);
                 } else {
                         mp->log = log;
                         mp->lsn = lsn;
 
                         /* insert bp after tblock in logsync list */
-                        LOGSYNC_LOCK(log, flags);
-
                         log->count++;
                         list_add(&mp->synclist, &tblk->synclist);
 
                         mp->clsn = tblk->clsn;
-                        LOGSYNC_UNLOCK(log, flags);
                 }
+                LOGSYNC_UNLOCK(log, flags);
         }
 
         /* write the last buffer. */