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 | 8 ++++++++ 1 file changed, 8 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 2011-05-01 06:35:17.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2011-05-01 06:35:19.000000000 +0800 @@ -431,6 +431,14 @@ writeback_single_inode(struct inode *ino requeue_io(inode, wb); } 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->for_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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/