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, 4 deletions

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index 87dd86c34c22..b62a048b6881 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -2844,11 +2844,11 @@ diUpdatePMap(struct inode *ipimap,
          */
         lsn = tblk->lsn;
         log = JFS_SBI(tblk->sb)->log;
+        LOGSYNC_LOCK(log, flags);
         if (mp->lsn != 0) {
                 /* inherit older/smaller lsn */
                 logdiff(difft, lsn, log);
                 logdiff(diffp, mp->lsn, log);
-                LOGSYNC_LOCK(log, flags);
                 if (difft < diffp) {
                         mp->lsn = lsn;
                         /* move mp after tblock in logsync list */
@@ -2860,17 +2860,15 @@ diUpdatePMap(struct inode *ipimap,
                 logdiff(diffp, mp->clsn, log);
                 if (difft > diffp)
                         mp->clsn = tblk->clsn;
-                LOGSYNC_UNLOCK(log, flags);
         } else {
                 mp->log = log;
                 mp->lsn = lsn;
                 /* insert mp 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_metapage(mp);
         return (0);
 }