jbd: abort instead of waiting for nonexistent transactions

The __log_wait_for_space function sits in a loop checkpointing
transactions until there is sufficient space free in the journal.
However, if there are no transactions to be processed (e.g.  because the
free space calculation is wrong due to a corrupted filesystem) it will
never progress.

Check for space being required when no transactions are outstanding and
abort the journal instead of endlessly looping.

This patch fixes the bug reported by Sami Liedes at:
http://bugzilla.kernel.org/show_bug.cgi?id=10976

Signed-off-by: Duane Griffin <duaneg@dghda.com>
Tested-by: Sami Liedes <sliedes@cc.hut.fi>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
index fe852193324302c3d1272b6a0ebe6d7ee4fc1122..1bd8d4acc6f2124a7574001d454a25b971fd9852 100644 (file)
--- a/fs/jbd/checkpoint.c
+++ b/fs/jbd/checkpoint.c
@@ -127,14 +127,29 @@ void __log_wait_for_space(journal_t *journal)
 
                /*
                 * Test again, another process may have checkpointed while we
-                * were waiting for the checkpoint lock
+                * were waiting for the checkpoint lock. If there are no
+                * outstanding transactions there is nothing to checkpoint and
+                * we can't make progress. Abort the journal in this case.
                 */
                spin_lock(&journal->j_state_lock);
+               spin_lock(&journal->j_list_lock);
                nblocks = jbd_space_needed(journal);
                if (__log_space_left(journal) < nblocks) {
+                       int chkpt = journal->j_checkpoint_transactions != NULL;
+
+                       spin_unlock(&journal->j_list_lock);
                        spin_unlock(&journal->j_state_lock);
-                       log_do_checkpoint(journal);
+                       if (chkpt) {
+                               log_do_checkpoint(journal);
+                       } else {
+                               printk(KERN_ERR "%s: no transactions\n",
+                                      __func__);
+                               journal_abort(journal, 0);
+                       }
+
                        spin_lock(&journal->j_state_lock);
+               } else {
+                       spin_unlock(&journal->j_list_lock);
                }
                mutex_unlock(&journal->j_checkpoint_mutex);
        }