linux-ext4 - jbd2-abort-instead-of-waiting-for-nonexistent-transactions.patch

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Message-Id: <20080922140851.bc3f9319.akpm@linux-foundation.org>
Date:	Mon, 22 Sep 2008 14:08:51 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Theodore Ts'o" <tytso@....edu>,
	"Stephen C. Tweedie" <sct@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: jbd2-abort-instead-of-waiting-for-nonexistent-transactions.patch


Guys, I have a note here that this might be needed in 2.6.27.

I also have a note that Stephen had issues with it, but I
don't recall what they were.

Can we get this sorted out please?



From: "Duane Griffin" <duaneg@...da.com>

The __jbd2_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@...da.com>
Cc: Sami Liedes <sliedes@...hut.fi>
Cc: <linux-ext4@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 fs/jbd2/checkpoint.c |   19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff -puN fs/jbd2/checkpoint.c~jbd2-abort-instead-of-waiting-for-nonexistent-transactions fs/jbd2/checkpoint.c
--- a/fs/jbd2/checkpoint.c~jbd2-abort-instead-of-waiting-for-nonexistent-transactions
+++ a/fs/jbd2/checkpoint.c
@@ -126,14 +126,29 @@ void __jbd2_log_wait_for_space(journal_t
 
 		/*
 		 * 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 (__jbd2_log_space_left(journal) < nblocks) {
+			int chkpt = journal->j_checkpoint_transactions != NULL;
+
+			spin_unlock(&journal->j_list_lock);
 			spin_unlock(&journal->j_state_lock);
-			jbd2_log_do_checkpoint(journal);
+			if (chkpt) {
+				jbd2_log_do_checkpoint(journal);
+			} else {
+				printk(KERN_ERR "%s: no transactions\n",
+				       __func__);
+				jbd2_journal_abort(journal, 0);
+			}
+
 			spin_lock(&journal->j_state_lock);
+		} else {
+			spin_unlock(&journal->j_list_lock);
 		}
 		mutex_unlock(&journal->j_checkpoint_mutex);
 	}
_

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