From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755216Ab1EFDgu (ORCPT ); Thu, 5 May 2011 23:36:50 -0400 Received: from mga09.intel.com ([134.134.136.24]:21301 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754097Ab1EFDgA (ORCPT ); Thu, 5 May 2011 23:36:00 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,324,1301900400"; d="scan'208";a="638817426" Message-Id: <20110506031612.043390260@intel.com> User-Agent: quilt/0.48-1 Date: Fri, 06 May 2011 11:08:23 +0800 From: Wu Fengguang To: Andrew Morton Cc: Wu Fengguang , LKML , Jan Kara cc: Dave Chinner cc: Christoph Hellwig cc: Subject: [PATCH 02/17] writeback: update dirtied_when for synced inode to prevent livelock References: <20110506030821.523093711@intel.com> Content-Disposition: inline; filename=writeback-fix-sync-busyloop.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With the more aggressive "keep writeback as long as we wrote something" logic in wb_writeback(), the "use LONG_MAX .nr_to_write" trick in commit b9543dac5bbc ("writeback: avoid livelocking WB_SYNC_ALL writeback") is no longer enough to stop sync livelock. The fix is to explicitly update .dirtied_when on synced inodes, so that they are no longer considered for writeback in the next round. CC: Jan Kara Signed-off-by: Wu Fengguang --- fs/fs-writeback.c | 9 +++++++++ 1 file changed, 9 insertions(+) ext3/ext4 are working fine now, however tests show that XFS may still livelock inside the XFS routines: [ 3581.181253] sync D ffff8800b6ca15d8 4560 4403 4392 0x00000000 [ 3581.181734] ffff88006f775bc8 0000000000000046 ffff8800b6ca12b8 00000001b6ca1938 [ 3581.182411] ffff88006f774000 00000000001d2e40 00000000001d2e40 ffff8800b6ca1280 [ 3581.183088] 00000000001d2e40 ffff88006f775fd8 00000340af111ef2 00000000001d2e40 [ 3581.183765] Call Trace: [ 3581.184008] [] ? lock_release_holdtime+0xa3/0xab [ 3581.184392] [] ? prepare_to_wait+0x6c/0x79 [ 3581.184756] [] ? prepare_to_wait+0x6c/0x79 [ 3581.185120] [] xfs_ioend_wait+0x87/0x9f [ 3581.185474] [] ? wake_up_bit+0x2a/0x2a [ 3581.185827] [] xfs_sync_inode_data+0x92/0x9d [ 3581.186198] [] xfs_inode_ag_walk+0x1a5/0x287 [ 3581.186569] [] ? xfs_inode_ag_walk+0x25e/0x287 [ 3581.186946] [] ? xfs_sync_worker+0x69/0x69 [ 3581.187311] [] ? xfs_perag_get+0x68/0xd0 [ 3581.187669] [] ? local_clock+0x41/0x5a [ 3581.188020] [] ? lock_release_holdtime+0xa3/0xab [ 3581.188403] [] ? xfs_check_sizes+0x160/0x160 [ 3581.188773] [] ? xfs_perag_get+0x68/0xd0 [ 3581.189130] [] ? xfs_perag_get+0x80/0xd0 [ 3581.189488] [] ? xfs_check_sizes+0x160/0x160 [ 3581.189858] [] ? xfs_inode_ag_iterator+0x6d/0x8f [ 3581.190241] [] ? xfs_sync_worker+0x69/0x69 [ 3581.190606] [] xfs_inode_ag_iterator+0x47/0x8f [ 3581.190982] [] ? __sync_filesystem+0x7a/0x7a [ 3581.191352] [] xfs_sync_data+0x24/0x43 [ 3581.191703] [] xfs_quiesce_data+0x2c/0x88 [ 3581.192065] [] xfs_fs_sync_fs+0x21/0x48 [ 3581.192419] [] __sync_filesystem+0x66/0x7a [ 3581.192783] [] sync_one_sb+0x16/0x18 [ 3581.193128] [] iterate_supers+0x72/0xce [ 3581.193482] [] sync_filesystems+0x20/0x22 [ 3581.193842] [] sys_sync+0x21/0x33 [ 3581.194177] [] system_call_fastpath+0x16/0x1b --- linux-next.orig/fs/fs-writeback.c 2011-05-05 23:30:22.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2011-05-05 23:30:23.000000000 +0800 @@ -432,6 +432,15 @@ writeback_single_inode(struct inode *ino requeue_io(inode); } else { /* + * sync livelock prevention: each inode is + * tagged and synced in one shot. If still + * dirty, move it back to s_dirty with updated + * dirty time to prevent syncing it again. + */ + if (wbc->sync_mode == WB_SYNC_ALL || + wbc->tagged_sync) + inode->dirtied_when = jiffies; + /* * Writeback blocked by something other than * congestion. Delay the inode for some time to * avoid spinning on the CPU (100% iowait)