linux-kernel - Re: Hang in XFS reclaim on 3.7.0-rc3

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Date:	Tue, 30 Oct 2012 09:26:13 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Torsten Kaiser <just.for.lkml@...glemail.com>
Cc:	xfs@....sgi.com, Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Hang in XFS reclaim on 3.7.0-rc3

On Mon, Oct 29, 2012 at 09:03:15PM +0100, Torsten Kaiser wrote:
> After experiencing a hang of all IO yesterday (
> http://marc.info/?l=linux-kernel&m=135142236520624&w=2 ), I turned on
> LOCKDEP after upgrading to -rc3.
> 
> I then tried to replicate the load that hung yesterday and got the
> following lockdep report, implicating XFS instead of by stacking swap
> onto dm-crypt and md.
> 
> [ 2844.971913]
> [ 2844.971920] =================================
> [ 2844.971921] [ INFO: inconsistent lock state ]
> [ 2844.971924] 3.7.0-rc3 #1 Not tainted
> [ 2844.971925] ---------------------------------
> [ 2844.971927] inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
> [ 2844.971929] kswapd0/725 [HC0[0]:SC0[0]:HE1:SE1] takes:
> [ 2844.971931] (&(&ip->i_lock)->mr_lock){++++?.}, at: [<ffffffff811e7ef4>] xfs_ilock+0x84/0xb0
> [ 2844.971941] {RECLAIM_FS-ON-W} state was registered at:
> [ 2844.971942]   [<ffffffff8108137e>] mark_held_locks+0x7e/0x130
> [ 2844.971947]   [<ffffffff81081a63>] lockdep_trace_alloc+0x63/0xc0
> [ 2844.971949]   [<ffffffff810e9dd5>] kmem_cache_alloc+0x35/0xe0
> [ 2844.971952]   [<ffffffff810dba31>] vm_map_ram+0x271/0x770
> [ 2844.971955]   [<ffffffff811e10a6>] _xfs_buf_map_pages+0x46/0xe0
> [ 2844.971959]   [<ffffffff811e1fba>] xfs_buf_get_map+0x8a/0x130
> [ 2844.971961]   [<ffffffff81233849>] xfs_trans_get_buf_map+0xa9/0xd0
> [ 2844.971964]   [<ffffffff8121e339>] xfs_ifree_cluster+0x129/0x670
> [ 2844.971967]   [<ffffffff8121f959>] xfs_ifree+0xe9/0xf0
> [ 2844.971969]   [<ffffffff811f4abf>] xfs_inactive+0x2af/0x480
> [ 2844.971972]   [<ffffffff811efb90>] xfs_fs_evict_inode+0x70/0x80
> [ 2844.971974]   [<ffffffff8110cb8f>] evict+0xaf/0x1b0
> [ 2844.971977]   [<ffffffff8110cd95>] iput+0x105/0x210
> [ 2844.971979]   [<ffffffff811070d0>] dentry_iput+0xa0/0xe0
> [ 2844.971981]   [<ffffffff81108310>] dput+0x150/0x280
> [ 2844.971983]   [<ffffffff811020fb>] sys_renameat+0x21b/0x290
> [ 2844.971986]   [<ffffffff81102186>] sys_rename+0x16/0x20
> [ 2844.971988]   [<ffffffff816b2292>] system_call_fastpath+0x16/0x1b

We shouldn't be mapping pages there. See if the patch below fixes
it.

Fundamentally, though, the lockdep warning has come about because
vm_map_ram is doing a GFP_KERNEL allocation when we need it to be
doing GFP_NOFS - we are within a transaction here, so memory reclaim
is not allowed to recurse back into the filesystem.

mm-folk: can we please get this vmalloc/gfp_flags passing API
fixed once and for all? This is the fourth time in the last month or
so that I've seen XFS bug reports with silent hangs and associated
lockdep output that implicate GFP_KERNEL allocations from vm_map_ram
in GFP_NOFS conditions as the potential cause....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com

xfs: don't vmap inode cluster buffers during free

From: Dave Chinner <dchinner@...hat.com>

Signed-off-by: Dave Chinner <dchinner@...hat.com>
---
 fs/xfs/xfs_inode.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index c4add46..82f6e5d 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1781,7 +1781,8 @@ xfs_ifree_cluster(
 		 * to mark all the active inodes on the buffer stale.
 		 */
 		bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, blkno,
-					mp->m_bsize * blks_per_cluster, 0);
+					mp->m_bsize * blks_per_cluster,
+					XBF_UNMAPPED);
 
 		if (!bp)
 			return ENOMEM;
--
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