jbd: protect all log tail updates with j_checkpoint_mutex

There are some log tail updates that are not protected by j_checkpoint_mutex.
Some of these are harmless because they happen during startup or shutdown but
updates in journal_commit_transaction() and journal_flush() can really race
with other log tail updates (e.g. someone doing journal_flush() with someone
running cleanup_journal_tail()). So protect all log tail updates with
j_checkpoint_mutex.

Signed-off-by: Jan Kara <jack@suse.cz>

2 files changed, 17 insertions, 1 deletions

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index dba9cfd75f1a..1b27f46e6108 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -308,7 +308,9 @@ void journal_commit_transaction(journal_t *journal)
         /* Do we need to erase the effects of a prior journal_flush? */
         if (journal->j_flags & JFS_FLUSHED) {
                 jbd_debug(3, "super block updated\n");
+                mutex_lock(&journal->j_checkpoint_mutex);
                 journal_update_sb_log_tail(journal);
+                mutex_unlock(&journal->j_checkpoint_mutex);
         } else {
                 jbd_debug(3, "superblock not updated\n");
         }
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index 44c104abfb36..b29c7678525d 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -936,8 +936,11 @@ static int journal_reset(journal_t *journal)
                         journal->j_errno);
                 journal->j_flags |= JFS_FLUSHED;
         } else {
+                /* Lock here to make assertions happy... */
+                mutex_lock(&journal->j_checkpoint_mutex);
                 /* Add the dynamic fields and write it to disk. */
                 journal_update_sb_log_tail(journal);
+                mutex_unlock(&journal->j_checkpoint_mutex);
         }
         return journal_start_thread(journal);
 }
@@ -1061,6 +1064,7 @@ void journal_update_sb_log_tail(journal_t *journal)
 {
         journal_superblock_t *sb = journal->j_superblock;
 
+        BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
         spin_lock(&journal->j_state_lock);
         jbd_debug(1,"JBD: updating superblock (start %u, seq %d, errno %d)\n",
                   journal->j_tail, journal->j_tail_sequence, journal->j_errno);
@@ -1089,6 +1093,7 @@ static void mark_journal_empty(journal_t *journal)
 {
         journal_superblock_t *sb = journal->j_superblock;
 
+        BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
         spin_lock(&journal->j_state_lock);
         jbd_debug(1, "JBD: Marking journal as empty (seq %d)\n",
                   journal->j_tail_sequence);
@@ -1293,6 +1298,8 @@ int journal_destroy(journal_t *journal)
 
         /* Force any old transactions to disk */
 
+        /* We cannot race with anybody but must keep assertions happy */
+        mutex_lock(&journal->j_checkpoint_mutex);
         /* Totally anal locking here... */
         spin_lock(&journal->j_list_lock);
         while (journal->j_checkpoint_transactions != NULL) {
@@ -1315,6 +1322,7 @@ int journal_destroy(journal_t *journal)
                         err = -EIO;
                 brelse(journal->j_sb_buffer);
         }
+        mutex_unlock(&journal->j_checkpoint_mutex);
 
         if (journal->j_inode)
                 iput(journal->j_inode);
@@ -1528,6 +1536,7 @@ int journal_flush(journal_t *journal)
         if (is_journal_aborted(journal))
                 return -EIO;
 
+        mutex_lock(&journal->j_checkpoint_mutex);
         cleanup_journal_tail(journal);
 
         /* Finally, mark the journal as really needing no recovery.
@@ -1536,6 +1545,7 @@ int journal_flush(journal_t *journal)
          * commits of data to the journal will restore the current
          * s_start value. */
         mark_journal_empty(journal);
+        mutex_unlock(&journal->j_checkpoint_mutex);
         spin_lock(&journal->j_state_lock);
         J_ASSERT(!journal->j_running_transaction);
         J_ASSERT(!journal->j_committing_transaction);
@@ -1576,8 +1586,12 @@ int journal_wipe(journal_t *journal, int write)
                 write ? "Clearing" : "Ignoring");
 
         err = journal_skip_recovery(journal);
-        if (write)
+        if (write) {
+                /* Lock to make assertions happy... */
+                mutex_lock(&journal->j_checkpoint_mutex);
                 mark_journal_empty(journal);
+                mutex_unlock(&journal->j_checkpoint_mutex);
+        }
 
  no_recovery:
         return err;