jbd2: 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 jbd2_journal_commit_transaction() and jbd2_journal_flush() can
really race with other log tail updates (e.g. someone doing
jbd2_journal_flush() with someone running jbd2_cleanup_journal_tail()). So
protect all log tail updates with j_checkpoint_mutex.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 18 insertions, 3 deletions

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 19371a8a9015..6705717d9b7f 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -340,7 +340,9 @@ void jbd2_journal_commit_transaction(journal_t *journal)
         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
         if (journal->j_flags & JBD2_FLUSHED) {
                 jbd_debug(3, "super block updated\n");
+                mutex_lock(&journal->j_checkpoint_mutex);
                 jbd2_journal_update_sb_log_tail(journal);
+                mutex_unlock(&journal->j_checkpoint_mutex);
         } else {
                 jbd_debug(3, "superblock not updated\n");
         }
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 6e75fbd75bad..fc5f2acc9f18 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1123,8 +1123,11 @@ static int journal_reset(journal_t *journal)
                         journal->j_errno);
                 journal->j_flags |= JBD2_FLUSHED;
         } else {
+                /* Lock here to make assertions happy... */
+                mutex_lock(&journal->j_checkpoint_mutex);
                 /* Add the dynamic fields and write it to disk. */
                 jbd2_journal_update_sb_log_tail(journal);
+                mutex_unlock(&journal->j_checkpoint_mutex);
         }
         return jbd2_journal_start_thread(journal);
 }
@@ -1173,6 +1176,7 @@ void jbd2_journal_update_sb_log_tail(journal_t *journal)
 {
         journal_superblock_t *sb = journal->j_superblock;
 
+        BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
         read_lock(&journal->j_state_lock);
         jbd_debug(1, "JBD2: updating superblock (start %ld, seq %d)\n",
                   journal->j_tail, journal->j_tail_sequence);
@@ -1201,6 +1205,7 @@ static void jbd2_mark_journal_empty(journal_t *journal)
 {
         journal_superblock_t *sb = journal->j_superblock;
 
+        BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
         read_lock(&journal->j_state_lock);
         jbd_debug(1, "JBD2: Marking journal as empty (seq %d)\n",
                   journal->j_tail_sequence);
@@ -1434,9 +1439,11 @@ int jbd2_journal_destroy(journal_t *journal)
         spin_unlock(&journal->j_list_lock);
 
         if (journal->j_sb_buffer) {
-                if (!is_journal_aborted(journal))
+                if (!is_journal_aborted(journal)) {
+                        mutex_lock(&journal->j_checkpoint_mutex);
                         jbd2_mark_journal_empty(journal);
-                else
+                        mutex_unlock(&journal->j_checkpoint_mutex);
+                } else
                         err = -EIO;
                 brelse(journal->j_sb_buffer);
         }
@@ -1630,6 +1637,7 @@ int jbd2_journal_flush(journal_t *journal)
         if (is_journal_aborted(journal))
                 return -EIO;
 
+        mutex_lock(&journal->j_checkpoint_mutex);
         jbd2_cleanup_journal_tail(journal);
 
         /* Finally, mark the journal as really needing no recovery.
@@ -1638,6 +1646,7 @@ int jbd2_journal_flush(journal_t *journal)
          * commits of data to the journal will restore the current
          * s_start value. */
         jbd2_mark_journal_empty(journal);
+        mutex_unlock(&journal->j_checkpoint_mutex);
         write_lock(&journal->j_state_lock);
         J_ASSERT(!journal->j_running_transaction);
         J_ASSERT(!journal->j_committing_transaction);
@@ -1678,8 +1687,12 @@ int jbd2_journal_wipe(journal_t *journal, int write)
                 write ? "Clearing" : "Ignoring");
 
         err = jbd2_journal_skip_recovery(journal);
-        if (write)
+        if (write) {
+                /* Lock to make assertions happy... */
+                mutex_lock(&journal->j_checkpoint_mutex);
                 jbd2_mark_journal_empty(journal);
+                mutex_unlock(&journal->j_checkpoint_mutex);
+        }
 
  no_recovery:
         return err;