linux-kernel - Re: XFS lock warning, 2.6.29-rc8

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Date:	Mon, 16 Mar 2009 09:19:21 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Denys Fedoryschenko <denys@...p.net.lb>
Cc:	xfs@....sgi.com, linux-kernel@...r.kernel.org
Subject: Re: XFS lock warning, 2.6.29-rc8

[ changed cc to xfs@....sgi.com. linux-xfs@...r.kernel.org does not
exist. ]

On Sun, Mar 15, 2009 at 02:59:01PM +0200, Denys Fedoryschenko wrote:
> hi
> 
> Here is what i got suddently. But seems everything is working.
> If any other information required, please let me know.

Known issue.

> [39993.560234] the existing dependency chain (in reverse order) is:
> [39993.560236]
> [39993.560236] -> #1 (&mm->mmap_sem){----}:
> [39993.560240]        [<ffffffff8105b9fc>] __lock_acquire+0x12b0/0x161a
> [39993.560244]        [<ffffffff8105bdbb>] lock_acquire+0x55/0x71
> [39993.560247]        [<ffffffff813fc2a5>] down_read+0x34/0x41
> [39993.560252]        [<ffffffff813ffbfe>] do_page_fault+0x3fa/0x848
> [39993.560256]        [<ffffffff813fda2f>] page_fault+0x1f/0x30
> [39993.560258]        [<ffffffff8107e13d>] generic_file_aio_read+0x35f/0x5da
> [39993.560268]        [<ffffffff811650d8>] xfs_read+0x17d/0x1f5
> [39993.560272]        [<ffffffff81161646>] xfs_file_aio_read+0x5f/0x61
> [39993.560275]        [<ffffffff810a88ff>] do_sync_read+0xe7/0x12d
> [39993.560284]        [<ffffffff810a928c>] vfs_read+0xab/0x134
> [39993.560287]        [<ffffffff810a93d9>] sys_read+0x47/0x6f
> [39993.560289]        [<ffffffff8100c0db>] system_call_fastpath+0x16/0x1b
> [39993.560293]        [<ffffffffffffffff>] 0xffffffffffffffff
> [39993.560302]
> [39993.560302] -> #0 (&(&ip->i_iolock)->mr_lock){----}:
> [39993.560306]        [<ffffffff8105b6cb>] __lock_acquire+0xf7f/0x161a
> [39993.560309]        [<ffffffff8105bdbb>] lock_acquire+0x55/0x71
> [39993.560312]        [<ffffffff8104ebde>] down_write_nested+0x37/0x46
> [39993.560316]        [<ffffffff811426aa>] xfs_ilock+0x27/0x79
> [39993.560318]        [<ffffffff8115b40e>] xfs_inactive+0x14d/0x411
> [39993.560322]        [<ffffffff8116552f>] xfs_fs_clear_inode+0x83/0x85
> [39993.560325]        [<ffffffff810ba8f7>] clear_inode+0x8a/0xe3
> [39993.560329]        [<ffffffff810bb044>] generic_delete_inode+0xf8/0x173
> [39993.560332]        [<ffffffff810bb0d6>] generic_drop_inode+0x17/0x1d5
> [39993.560335]        [<ffffffff810ba1c7>] iput+0x61/0x65
> [39993.560338]        [<ffffffff810b7554>] dentry_iput+0xa9/0xc1
> [39993.560341]        [<ffffffff810b7651>] d_kill+0x40/0x60
> [39993.560344]        [<ffffffff810b942d>] dput+0x141/0x14e
> [39993.560347]        [<ffffffff810a9a85>] __fput+0x173/0x198
> [39993.560350]        [<ffffffff810a9ac2>] fput+0x18/0x1a
> [39993.560353]        [<ffffffff8109411e>] remove_vma+0x3e/0x63
> [39993.560355]        [<ffffffff8109503c>] do_munmap+0x2e9/0x30b
> [39993.560358]        [<ffffffff8109509e>] sys_munmap+0x40/0x59
> [39993.560361]        [<ffffffff8100c0db>] system_call_fastpath+0x16/0x1b
> [39993.560363]        [<ffffffffffffffff>] 0xffffffffffffffff

This is a VM problem where it calls fput() with the mmap_sem() held
in remove_vma(). It makes the incorrect assumption that filesystems
will never use the same lock in the IO path and the inode release path.

This can deadlock if you are really unlucky.

Cheers,

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