From: Josef Bacik Subject: Re: [PATCH] Fix DIO EIO error caused by race between jbd_commit_transaction() and journal_try_to_drop_buffers() Date: Fri, 16 May 2008 11:01:46 -0400 Message-ID: <20080516150146.GA21018@unused.rdu.redhat.com> References: <20080505170636.GK25722@duck.suse.cz> <1210372072.3639.52.camel@localhost.localdomain> <20080512155419.GD15856@duck.suse.cz> <1210639184.3661.43.camel@localhost.localdomain> <20080513145449.GC20806@duck.suse.cz> <1210717389.3638.24.camel@localhost.localdomain> <20080514170856.GH24363@duck.suse.cz> <1210786872.3657.48.camel@localhost.localdomain> <20080514181444.GI24363@duck.suse.cz> <1210947250.3608.18.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , Badari Pulavarty , akpm@linux-foundation.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: Mingming Cao Return-path: Received: from mx1.redhat.com ([66.187.233.31]:49488 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758901AbYEPPTx (ORCPT ); Fri, 16 May 2008 11:19:53 -0400 Content-Disposition: inline In-Reply-To: <1210947250.3608.18.camel@localhost.localdomain> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, May 16, 2008 at 07:14:10AM -0700, Mingming Cao wrote: > This patch fixed a few races between direct IO and kjournld commit transaction. > An unexpected EIO error gets returned to direct IO caller when it failed to > free those data buffers. This could be reproduced easily with parallel > direct write and buffered write to the same file > > More specific, those races could cause journal_try_to_free_buffers() > fail to free the data buffers, when jbd is committing the transaction that has > those data buffers on its t_syncdata_list or t_locked_list. > journal_commit_transaction() still holds the reference to those buffers > before data reach to disk and buffers are removed from the > t_syncdata_list of t_locked_list. This prevent the concurrent > journal_try_to_free_buffers() to free those buffers at the same time, and cause > EIO error returns back to direct IO. > > With this patch, in case of direct IO and when try_to_free_buffers() failed, > let's waiting for journal_commit_transaction() to finish > flushing the current committing transaction's data buffers to disk, > then try to free those buffers again. > > Signed-off-by: Mingming Cao > Reviewed-by: Badari Pulavarty > --- > fs/jbd/commit.c | 1 + > fs/jbd/journal.c | 1 + > fs/jbd/transaction.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/jbd.h | 3 +++ > 4 files changed, 51 insertions(+) > > Index: linux-2.6.26-rc1/include/linux/jbd.h > =================================================================== > --- linux-2.6.26-rc1.orig/include/linux/jbd.h 2008-05-14 16:36:41.000000000 -0700 > +++ linux-2.6.26-rc1/include/linux/jbd.h 2008-05-15 14:12:10.000000000 -0700 > @@ -667,6 +667,9 @@ struct journal_s > */ > wait_queue_head_t j_wait_transaction_locked; > > + /* Wait queu for waiting for data buffers to flushed to disk*/ > + wait_queue_head_t j_wait_data_flushed; > + > /* Wait queue for waiting for checkpointing to complete */ > wait_queue_head_t j_wait_logspace; > > Index: linux-2.6.26-rc1/fs/jbd/commit.c > =================================================================== > --- linux-2.6.26-rc1.orig/fs/jbd/commit.c 2008-05-03 11:59:44.000000000 -0700 > +++ linux-2.6.26-rc1/fs/jbd/commit.c 2008-05-15 14:12:46.000000000 -0700 > @@ -462,6 +462,7 @@ void journal_commit_transaction(journal_ > * clean by now, so check that it is in fact empty. > */ > J_ASSERT (commit_transaction->t_sync_datalist == NULL); > + wake_up(&journal->j_wait_data_flushed) > > jbd_debug (3, "JBD: commit phase 3\n"); > > Index: linux-2.6.26-rc1/fs/jbd/journal.c > =================================================================== > --- linux-2.6.26-rc1.orig/fs/jbd/journal.c 2008-05-14 16:36:41.000000000 -0700 > +++ linux-2.6.26-rc1/fs/jbd/journal.c 2008-05-15 14:13:02.000000000 -0700 > @@ -660,6 +660,7 @@ static journal_t * journal_init_common ( > goto fail; > > init_waitqueue_head(&journal->j_wait_transaction_locked); > + init_waitqueue_head(&journal->j_wait_data_flushed); > init_waitqueue_head(&journal->j_wait_logspace); > init_waitqueue_head(&journal->j_wait_done_commit); > init_waitqueue_head(&journal->j_wait_checkpoint); > Index: linux-2.6.26-rc1/fs/jbd/transaction.c > =================================================================== > --- linux-2.6.26-rc1.orig/fs/jbd/transaction.c 2008-05-03 11:59:44.000000000 -0700 > +++ linux-2.6.26-rc1/fs/jbd/transaction.c 2008-05-16 06:42:30.000000000 -0700 > @@ -1648,12 +1648,47 @@ out: > return; > } > > +/* > + * Journal_try_to_free_buffers() will call this function to w > + * waiting for the current transaction finishing syncing data buffers, before > + * try to free that buffer. > + * > + * journal_try_to_free_buffers() could race with journal_commit_transaction() > + * The later might still hold the reference count to the buffers when inspecting > + * them on t_syncdata_list or t_locked_list. > + */ > +static void journal_wait_for_transaction_sync_data(journal_t *journal) > +{ > + transaction_t *transaction = NULL; > + > + transaction = journal->j_committing_transaction; > + > + if (!transaction) > + return; > + > + /* > + * If the current transaction is flushing and waiting for data buffers > + * (t_state is T_FLUSH), wait for the j_wait_data_flushed event > + */ > + if (transaction->t_state == T_FLUSH) { > + DEFINE_WAIT(wait); > + > + prepare_to_wait(&journal->j_wait_data_flushed, > + &wait, TASK_UNINTERRUPTIBLE); > + spin_unlock(&journal->j_state_lock); > + schedule(); > + finish_wait(&journal->j_wait_data_flushed, &wait); > + spin_lock(&journal->j_state_lock); > + } > + return; > +} > Got a couple of whitespace problems above it looks like. Thanks, Josef