From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q4OG7FPw031807 for ; Thu, 24 May 2012 11:07:16 -0500 Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id fguCF89KLub9WOVz for ; Thu, 24 May 2012 09:07:13 -0700 (PDT) Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q4OG7BfU032327 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 24 May 2012 12:07:11 -0400 From: Brian Foster Subject: [PATCH] xfs: re-enable xfsaild idle mode and fix associated races Date: Thu, 24 May 2012 12:06:42 -0400 Message-Id: <1337875602-63025-1-git-send-email-bfoster@redhat.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: xfs@oss.sgi.com Cc: Brian Foster xfsaild idle mode logic currently leads to a couple hangs: 1.) If xfsaild is rescheduled in during an incremental scan (i.e., tout != 0) and the target has been updated since the previous run, we can hit the new target and go into idle mode with a still populated ail. 2.) A wake up is only issued when the target is pushed forward. The wake up can race with xfsaild if it is currently in the process of entering idle mode, causing future wake up events to be lost. Both hangs are reproducible by running xfstests 273 in a loop. Modify xfsaild to enter idle mode only when the ail is empty and the push target has not been moved forward since the last push. Signed-off-by: Brian Foster --- This is a lightly tested version against the xfs tree. I'll be more heavily testing a version based on my upstream reproducer tree over the next few days followed by similar testing on this patch if all goes well. Sending in advance for review. fs/xfs/xfs_trans_ail.c | 29 ++++++++++++++++++++++++++--- fs/xfs/xfs_trans_priv.h | 1 + 2 files changed, 27 insertions(+), 3 deletions(-) diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c index 9c51448..0819cd3 100644 --- a/fs/xfs/xfs_trans_ail.c +++ b/fs/xfs/xfs_trans_ail.c @@ -383,6 +383,12 @@ xfsaild_push( } spin_lock(&ailp->xa_lock); + + /* barrier matches the xa_target update in xfs_ail_push() */ + smp_rmb(); + target = ailp->xa_target; + ailp->xa_target_prev = target; + lip = xfs_trans_ail_cursor_first(ailp, &cur, ailp->xa_last_pushed_lsn); if (!lip) { /* @@ -397,7 +403,6 @@ xfsaild_push( XFS_STATS_INC(xs_push_ail); lsn = lip->li_lsn; - target = ailp->xa_target; while ((XFS_LSN_CMP(lip->li_lsn, target) <= 0)) { int lock_result; @@ -527,8 +532,26 @@ xfsaild( __set_current_state(TASK_KILLABLE); else __set_current_state(TASK_INTERRUPTIBLE); - schedule_timeout(tout ? - msecs_to_jiffies(tout) : MAX_SCHEDULE_TIMEOUT); + + spin_lock(&ailp->xa_lock); + + /* barrier matches the xa_target update in xfs_ail_push() */ + smp_rmb(); + if (!xfs_ail_min(ailp) && (ailp->xa_target == ailp->xa_target_prev)) { + /* the ail is empty and no change to the push target - idle */ + spin_unlock(&ailp->xa_lock); + schedule(); + tout = 0; + continue; + } + spin_unlock(&ailp->xa_lock); + + if (tout) { + /* more work to do soon */ + schedule_timeout(msecs_to_jiffies(tout)); + } + + __set_current_state(TASK_RUNNING); try_to_freeze(); diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h index fb62377..53b7c9b 100644 --- a/fs/xfs/xfs_trans_priv.h +++ b/fs/xfs/xfs_trans_priv.h @@ -67,6 +67,7 @@ struct xfs_ail { struct task_struct *xa_task; struct list_head xa_ail; xfs_lsn_t xa_target; + xfs_lsn_t xa_target_prev; struct list_head xa_cursors; spinlock_t xa_lock; xfs_lsn_t xa_last_pushed_lsn; -- 1.7.7.6 _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs