linux-ext4 - [PATCH] jbd: clear b_modified before moving the jh to a different transaction

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Date:	Tue, 10 Jan 2012 13:12:55 -0500
From:	Josef Bacik <josef@...hat.com>
To:	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	jack@...e.cz
Subject: [PATCH] jbd: clear b_modified before moving the jh to a different transaction

If we are journalling data (ie journal=data or big symlinks) we can discard
buffers and move them to different transactions to make sure they get cleaned up
properly.  The problem is b_modified could still be set from the last
transaction that touched it, so putting it on the currently running transaction
or setting it up to be put on the next transaction will run into problems if the
buffer gets reused in that transaction as the space accounting logic won't be
done, which will result in panics at commit time because t_nr_buffers will end
up being more than t_outstanding_credits.  Thanks to Jan Kara for pointing out
the other part of this problem a few months ago.  Thanks,

Signed-off-by: Josef Bacik <josef@...hat.com>
---
 fs/jbd/transaction.c  |    5 ++++-
 fs/jbd2/transaction.c |    5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
index 7e59c6e..c968788 100644
--- a/fs/jbd/transaction.c
+++ b/fs/jbd/transaction.c
@@ -1784,6 +1784,7 @@ static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
 		 */
 		clear_buffer_dirty(bh);
 		__journal_file_buffer(jh, transaction, BJ_Forget);
+		jh->b_modified = 0;
 		may_free = 0;
 	} else {
 		JBUFFER_TRACE(jh, "on running transaction");
@@ -1952,8 +1953,10 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
 		 * clear dirty bits when it is done with the buffer.
 		 */
 		set_buffer_freed(bh);
-		if (journal->j_running_transaction && buffer_jbddirty(bh))
+		if (journal->j_running_transaction && buffer_jbddirty(bh)) {
+			jh->b_modified = 0;
 			jh->b_next_transaction = journal->j_running_transaction;
+		}
 		journal_put_journal_head(jh);
 		spin_unlock(&journal->j_list_lock);
 		jbd_unlock_bh_state(bh);
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index a0e41a4..094dcd8 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1756,6 +1756,7 @@ static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
 		 * __journal_file_buffer
 		 */
 		clear_buffer_dirty(bh);
+		jh->b_modified = 0;
 		__jbd2_journal_file_buffer(jh, transaction, BJ_Forget);
 		may_free = 0;
 	} else {
@@ -1917,8 +1918,10 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
 		 * clear dirty bits when it is done with the buffer.
 		 */
 		set_buffer_freed(bh);
-		if (journal->j_running_transaction && buffer_jbddirty(bh))
+		if (journal->j_running_transaction && buffer_jbddirty(bh)) {
+			jh->b_modified = 0;
 			jh->b_next_transaction = journal->j_running_transaction;
+		}
 		jbd2_journal_put_journal_head(jh);
 		spin_unlock(&journal->j_list_lock);
 		jbd_unlock_bh_state(bh);
-- 
1.7.5.2

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