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Date: Tue, 29 Jul 2014 17:23:33 -0400
From: Matthew Wilcox <willy@...ux.intel.com>
To: Jan Kara <jack@...e.cz>
Cc: Matthew Wilcox <matthew.r.wilcox@...el.com>,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 07/22] Replace the XIP page fault handler with the DAX
page fault handler
On Tue, Jul 29, 2014 at 11:04:57PM +0200, Jan Kara wrote:
> > Path 1:
> >
> > ext4_fallocate ->
> > ext4_punch_hole ->
> > ext4_inode_attach_jinode() -> ... ->
> > lock_map_acquire(&handle->h_lockdep_map);
> > truncate_pagecache_range() ->
> > unmap_mapping_range() ->
> > mutex_lock(&mapping->i_mmap_mutex);
> This is strange. I don't see how ext4_inode_attach_jinode() can ever lead
> to lock_map_acquire(&handle->h_lockdep_map). Can you post a full trace for
> this?
Unfortunately, lockdep finds the inversion in the other order, so I
have the backtraces of this path hitting the i_mmap_mutex while already
holding jbd_mutex:
======================================================
[ INFO: possible circular locking dependency detected ]
3.16.0-rc6+ #91 Tainted: G W
-------------------------------------------------------
fstest/31836 is trying to acquire lock:
(jbd2_handle){+.+.+.}, at: [<ffffffffa00f5333>] start_this_handle+0x193/0x630 [jbd2]
but task is already holding lock:
(&mapping->i_mmap_mutex){+.+...}, at: [<ffffffff8124c0a0>] do_dax_fault+0x4e0/0x640
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&mapping->i_mmap_mutex){+.+...}:
[<ffffffff810cfa22>] lock_acquire+0xb2/0x1f0
[<ffffffff815cad15>] mutex_lock_nested+0x75/0x420
[<ffffffff811acf4b>] unmap_mapping_range+0x6b/0x180
[<ffffffff811901ba>] truncate_pagecache_range+0x4a/0x60
[<ffffffffa020af41>] ext4_punch_hole+0x4d1/0x530 [ext4]
[<ffffffffa0235356>] ext4_fallocate+0x156/0xb70 [ext4]
[<ffffffff811f3c19>] do_fallocate+0x119/0x1b0
[<ffffffff811f3cf3>] SyS_fallocate+0x43/0x70
[<ffffffff815cf8a9>] system_call_fastpath+0x16/0x1b
-> #0 (jbd2_handle){+.+.+.}:
[<ffffffff810ce9e1>] __lock_acquire+0x1d01/0x1eb0
[<ffffffff810cfa22>] lock_acquire+0xb2/0x1f0
[<ffffffffa00f538e>] start_this_handle+0x1ee/0x630 [jbd2]
[<ffffffffa00f5c04>] jbd2__journal_start+0xd4/0x260 [jbd2]
[<ffffffffa0235f6d>] __ext4_journal_start_sb+0x6d/0x190 [ext4]
[<ffffffffa0206fca>] _ext4_get_block+0x16a/0x1c0 [ext4]
[<ffffffffa0207036>] ext4_get_block+0x16/0x20 [ext4]
[<ffffffff8124c199>] do_dax_fault+0x5d9/0x640
[<ffffffff8124c23f>] dax_fault+0x3f/0x90
[<ffffffffa01ff975>] ext4_dax_fault+0x15/0x20 [ext4]
[<ffffffff811ab6d1>] __do_fault+0x41/0xd0
[<ffffffff811ae7f5>] do_shared_fault.isra.56+0x35/0x220
[<ffffffff811af983>] handle_mm_fault+0x303/0xf70
[<ffffffff81062d2c>] __do_page_fault+0x1ec/0x5b0
[<ffffffff81063112>] do_page_fault+0x22/0x30
[<ffffffff815d18b8>] page_fault+0x28/0x30
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mapping->i_mmap_mutex);
lock(jbd2_handle);
lock(&mapping->i_mmap_mutex);
lock(jbd2_handle);
*** DEADLOCK ***
3 locks held by fstest/31836:
#0: (&mm->mmap_sem){++++++}, at: [<ffffffff81062cc2>] __do_page_fault+0x182/0x5b0
#1: (sb_pagefaults){++++..}, at: [<ffffffff8124c27a>] dax_fault+0x7a/0x90
#2: (&mapping->i_mmap_mutex){+.+...}, at: [<ffffffff8124c0a0>] do_dax_fault+0x4e0/0x640
stack backtrace:
CPU: 6 PID: 31836 Comm: fstest Tainted: G W 3.16.0-rc6+ #91
Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./Q87M-D2H, BIOS F6 08/03/2013
ffffffff825e63e0 ffff8800a0fc78c0 ffffffff815c6bc3 ffffffff825e63e0
ffff8800a0fc7900 ffffffff815c4e59 ffff8800a0fc7970 ffff8800a88f4a50
ffff8800a88f4af8 ffff8800a88f5280 0000000000000003 ffff8800a88f5248
Call Trace:
[<ffffffff815c6bc3>] dump_stack+0x4d/0x66
[<ffffffff815c4e59>] print_circular_bug+0x201/0x20f
[<ffffffff810ce9e1>] __lock_acquire+0x1d01/0x1eb0
[<ffffffff81023b00>] ? cyc2ns_read_end+0x20/0x20
[<ffffffff810cfa22>] lock_acquire+0xb2/0x1f0
[<ffffffffa00f5333>] ? start_this_handle+0x193/0x630 [jbd2]
[<ffffffffa00f538e>] start_this_handle+0x1ee/0x630 [jbd2]
[<ffffffffa00f5333>] ? start_this_handle+0x193/0x630 [jbd2]
[<ffffffffa00f5020>] ? new_handle+0x20/0x60 [jbd2]
[<ffffffffa00f5c04>] jbd2__journal_start+0xd4/0x260 [jbd2]
[<ffffffffa0206fca>] ? _ext4_get_block+0x16a/0x1c0 [ext4]
[<ffffffffa0235f6d>] __ext4_journal_start_sb+0x6d/0x190 [ext4]
[<ffffffffa0206fca>] _ext4_get_block+0x16a/0x1c0 [ext4]
[<ffffffffa0207036>] ext4_get_block+0x16/0x20 [ext4]
[<ffffffff8124c199>] do_dax_fault+0x5d9/0x640
[<ffffffffa0207020>] ? _ext4_get_block+0x1c0/0x1c0 [ext4]
[<ffffffffa0207020>] ? _ext4_get_block+0x1c0/0x1c0 [ext4]
[<ffffffff8124c23f>] dax_fault+0x3f/0x90
[<ffffffffa01ff975>] ext4_dax_fault+0x15/0x20 [ext4]
[<ffffffff811ab6d1>] __do_fault+0x41/0xd0
[<ffffffff811ae7f5>] do_shared_fault.isra.56+0x35/0x220
[<ffffffff811af983>] handle_mm_fault+0x303/0xf70
[<ffffffff810ca676>] ? __lock_is_held+0x56/0x80
[<ffffffff81062d2c>] __do_page_fault+0x1ec/0x5b0
[<ffffffff8119dc3c>] ? vm_mmap_pgoff+0x9c/0xc0
[<ffffffff810c80cf>] ? up_write+0x1f/0x40
[<ffffffff8119dc3c>] ? vm_mmap_pgoff+0x9c/0xc0
[<ffffffff8133e1ea>] ? trace_hardirqs_off_thunk+0x3a/0x3c
[<ffffffff81063112>] do_page_fault+0x22/0x30
[<ffffffff815d18b8>] page_fault+0x28/0x30
--
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