Date:	Thu, 7 Nov 2013 11:17:22 -0800
From:	Olof Johansson <olof@...om.net>
To:	Dave Kleikamp <dave.kleikamp@...cle.com>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Jens Axboe <axboe@...nel.dk>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Zach Brown <zab@...bo.net>, Kent Overstreet <kmo@...erainc.com>
Subject: Re: linux-next: manual merge of the block tree with the tree

On Sat, Nov 2, 2013 at 1:50 PM, Dave Kleikamp <dave.kleikamp@...cle.com> wrote:
> On 11/01/2013 03:53 PM, Jens Axboe wrote:
>> On 11/01/2013 02:41 PM, Dave Kleikamp wrote:
>>> On 11/01/2013 03:27 PM, Jens Axboe wrote:
>>>> On 11/01/2013 02:22 PM, Stephen Rothwell wrote:
>>>>> Hi Jens,
>>>>>
>>>>> On Fri, 01 Nov 2013 09:10:43 -0600 Jens Axboe <axboe@...nel.dk> wrote:
>>>>>>
>>>>>> On 10/31/2013 09:20 PM, Stephen Rothwell wrote:
>>>>>>>
>>>>>>> Today's linux-next merge of the block tree got a conflict in
>>>>>>> drivers/block/loop.c between commit 2486740b52fd ("loop: use aio to
>>>>>>> perform io on the underlying file") from the aio-direct tree and commit
>>>>>>> ed2d2f9a8265 ("block: Abstract out bvec iterator") from the block tree.
>>>>>>>
>>>>>>> I fixed it up (I think - see below - I have also attached the final
>>>>>>> resulting file) and can carry the fix as necessary (no action is
>>>>>>> required).
>>>>>>>
>>>>>>
>>>>>> What tree is this from? It'd be a lot more convenient to fold that loop
>>>>>> patch into my tree, especially since the block tree in linux-next failed
>>>>>> after this merge.
>>>>>
>>>>> I can only agree with you.  It is from the aio-direct tree (probably
>>>>> misnamed by me) (git://github.com/kleikamp/linux-shaggy.git#for-next) run
>>>>> by Dave Kleikamp.
>>>>
>>>> Dave, input requested.
>>>>
>>>> In any case, I would suggest dropping the aio-direct tree instead of the
>>>> entire block tree for coverage purposes, if merge or build failures
>>>> happen because of it.
>>>
>>> I've had these patches in linux-next since August, and I'd really like
>>> to push them in the 3.13 merge window.
>>>
>>> Are there other problems besides this merge issue? I'll take a closer
>>> look at Stephen's merge patch and see if I find any other issues, but I
>>> really don't want to pull these patches out of linux-next now.
>>
>> I'm not saying that the patches should be dropped or not go into 3.13.
>> What I'm saying is that if the choice is between having the bio and
>> blk-mq stuff in linux-next or an addon to the loop driver, the decision
>> should be quite clear.
>>
>> So we've three immediate options:
>>
>> 1) You base it on top of the block tree
>> 2) I carry the loop updates
>> 3) You hand Stephen a merge patch for the resulting merge of the two
>
> Attached is a merge patch and the merged loop.c. I'm having problems
> with the loop driver with both the block and my tree. I'll continue to
> look at that, but everything should build cleanly with this.

Hijacking(?) this thread since it seems relevant:

I noticed the following panic on a chromebox with last night's next.
20131106 shows it as well. I didn't go back further to see. 3.12 runs
fine.

I bisected it down, and unfortunately it points at Stephen's merge commit:

commit 3caa8f38e7eeb56c7d48b0d5c323ffbf4939635d
Merge: 447b374 bb6f7be
Author: Stephen Rothwell <sfr@...b.auug.org.au>
Date:   Thu Nov 7 14:07:20 2013 +1100

    Merge remote-tracking branch 'aio-direct/for-next'

    Conflicts:
        drivers/block/loop.c
        fs/nfs/direct.c
        fs/nfs/file.c
        include/linux/blk_types.h


... but the branch alone runs fine.

Context to the failure: Userspace is already up and running. ChromeOS
will do ecryptfs and loopback mounts, etc, which is likely where this
is hitting given the process running. It definitely happens during
early userspace setup.

Seems like we might be in for a bumpy ride in 3.13 w.r.t. block if the
breakage we've found this week in -next is any indication.

This seems to be reliably reproducing for me so I can help collect
data if needed, Dave/Jens.

[    3.373979] EXT4-fs (sda1): mounted filesystem with ordered data
mode. Opts: commit=600
[    3.385719] EXT4-fs (sda8): mounted filesystem with ordered data
mode. Opts: commit=600
[    3.475540] bio: create slab <bio-1> at 1
[    3.483577] EXT4-fs (dm-0): mounted filesystem with ordered data
mode. Opts: discard,commit=600
[    3.556890] EXT4-fs (sda1): re-mounted. Opts: commit=600,data=ordered
[    3.636658] ------------[ cut here ]------------
[    3.641345] kernel BUG at
/mnt/host/source/src/third_party/kernel-next/fs/bio.c:1725!
[    3.649266] invalid opcode: 0000 [#1] SMP
[    3.653473] Modules linked in:
[    3.656610] CPU: 0 PID: 107 Comm: loop0 Tainted: G        W
3.12.0-next-20131107 #6
[    3.664645] Hardware name: SAMSUNG Stumpy, BIOS
Google_Stumpy.2183.0.2012_05_01_1303 05/01/2012
[    3.673463] task: ffff88010001e250 ti: ffff880074c7e000 task.ti:
ffff880074c7e000
[    3.681023] RIP: 0010:[<ffffffff8111229d>]  [<ffffffff8111229d>]
bio_endio+0x13/0x59
[    3.688887] RSP: 0018:ffff880074c7fc50  EFLAGS: 00010246
[    3.694272] RAX: 0000000000000000 RBX: ffff880074cb6120 RCX: 0000000000000000
[    3.701496] RDX: 00000000fffffffb RSI: fffffffffffffffb RDI: ffff880074c4b000
[    3.708728] RBP: ffff880074c7fc58 R08: 00000000002df000 R09: 0000000000000200
[    3.715968] R10: 0000000000000000 R11: ffff880074cb6120 R12: ffffffffffffffff
[    3.723198] R13: ffffffffffffffea R14: 0000000000010000 R15: 000000000000001f
[    3.730439] FS:  0000000000000000(0000) GS:ffff880100200000(0000)
knlGS:0000000000000000
[    3.738590] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    3.744383] CR2: 00007fd88c159080 CR3: 000000000180c000 CR4: 00000000000407f0
[    3.751605] Stack:
[    3.753657]  ffffffff813369b4 ffff880074c7fc98 ffffffff8111f64f
00000000002df000
[    3.761280]  ffff880074cb6120 ffff880074c19000 ffff880074cb6120
0000000000010000
[    3.768848]  000000000000001f ffff880074c7fd08 ffffffff8111fb00
ffff880075e9a200
[    3.776419] Call Trace:
[    3.778900]  [<ffffffff813369b4>] ? lo_rw_aio_complete+0x23/0x25
[    3.785038]  [<ffffffff8111f64f>] aio_complete+0x4a/0x1f7
[    3.790535]  [<ffffffff8111fb00>] aio_run_iocb.isra.13+0x304/0x329
[    3.796781]  [<ffffffff8111f041>] ? kzalloc+0xf/0x11
[    3.801837]  [<ffffffff8111fb53>] aio_kernel_submit+0x2e/0x45
[    3.807658]  [<ffffffff81337349>] lo_rw_aio+0x1aa/0x1cf
[    3.812940]  [<ffffffff813378d7>] loop_thread+0x2cf/0x4e7
[    3.818408]  [<ffffffff8104eca6>] ? bit_waitqueue+0x7a/0x7a
[    3.824009]  [<ffffffff81337608>] ? loop_attr_do_show_autoclear+0x1a/0x1a
[    3.830901]  [<ffffffff8104e867>] kthread+0xea/0xf2
[    3.835857]  [<ffffffff8104e77d>] ? flush_kthread_worker+0xba/0xba
[    3.842085]  [<ffffffff814cb8ac>] ret_from_fork+0x7c/0xb0
[    3.847564]  [<ffffffff8104e77d>] ? flush_kthread_worker+0xba/0xba
[    3.853815] Code: 83 c3 10 41 0f b7 45 58 41 39 c4 7c b7 31 c0 5b
41 5c 41 5d 41 5e 5d c3 66 66 66 66 90 ba fb ff ff ff eb 37 8b 47 44
85 c0 7f 02 <0f> 0b 85 f6 74 07 f0 80 67 10 fe eb 09 48 8b 47 10 a8 01
0f 44
[    3.874480] RIP  [<ffffffff8111229d>] bio_endio+0x13/0x59
[    3.880004]  RSP <ffff880074c7fc50>
[    3.883602] ---[ end trace ead15c309b799920 ]---
[    3.888283] Kernel panic - not syncing: Fatal exception
[    3.893581] Kernel Offset: 0x0 from 0xffffffff81000000 (relocation
range: 0xffffffff80000000-0xffffffff9fffffff)
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