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Message-ID: <f10de555-370b-f236-1107-e3089258ebbc@fujitsu.com>
Date:   Tue, 27 Sep 2022 14:53:14 +0800
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Subject: Re: [RFC PATCH] xfs: drop experimental warning for fsdax
To:     Dave Chinner <david@fromorbit.com>
CC:     <linux-kernel@vger.kernel.org>, <linux-xfs@vger.kernel.org>,
        <nvdimm@lists.linux.dev>, <linux-mm@kvack.org>,
        <linux-fsdevel@vger.kernel.org>, <djwong@kernel.org>,
        <dan.j.williams@intel.com>
References: <1663234002-17-1-git-send-email-ruansy.fnst@fujitsu.com>
 <20220919045003.GJ3600936@dread.disaster.area>
 <20220919211533.GK3600936@dread.disaster.area>
From:   Shiyang Ruan <ruansy.fnst@fujitsu.com>
In-Reply-To: <20220919211533.GK3600936@dread.disaster.area>
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在 2022/9/20 5:15, Dave Chinner 写道:
> On Mon, Sep 19, 2022 at 02:50:03PM +1000, Dave Chinner wrote:
>> On Thu, Sep 15, 2022 at 09:26:42AM +0000, Shiyang Ruan wrote:
>>> Since reflink&fsdax can work together now, the last obstacle has been
>>> resolved.  It's time to remove restrictions and drop this warning.
>>>
>>> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
>>
>> I haven't looked at reflink+DAX for some time, and I haven't tested
>> it for even longer. So I'm currently running a v6.0-rc6 kernel with
>> "-o dax=always" fstests run with reflink enabled and it's not
>> looking very promising.
>>
>> All of the fsx tests are failing with data corruption, several
>> reflink/clone tests are failing with -EINVAL (e.g. g/16[45]) and
>> *lots* of tests are leaving stack traces from WARN() conditions in
>> DAx operations such as dax_insert_entry(), dax_disassociate_entry(),
>> dax_writeback_mapping_range(), iomap_iter() (called from
>> dax_dedupe_file_range_compare()), and so on.
>>
>> At thsi point - the tests are still running - I'd guess that there's
>> going to be at least 50 test failures by the time it completes -
>> in comparison using "-o dax=never" results in just a single test
>> failure and a lot more tests actually being run.
> 
> The end results with dax+reflink were:
> 
> SECTION       -- xfs_dax
> =========================
> 
> Failures: generic/051 generic/068 generic/074 generic/075
> generic/083 generic/091 generic/112 generic/127 generic/164
> generic/165 generic/175 generic/231 generic/232 generic/247
> generic/269 generic/270 generic/327 generic/340 generic/388
> generic/390 generic/413 generic/447 generic/461 generic/471
> generic/476 generic/517 generic/519 generic/560 generic/561
> generic/605 generic/617 generic/619 generic/630 generic/649
> generic/650 generic/656 generic/670 generic/672 xfs/011 xfs/013
> xfs/017 xfs/068 xfs/073 xfs/104 xfs/127 xfs/137 xfs/141 xfs/158
> xfs/168 xfs/179 xfs/243 xfs/297 xfs/305 xfs/328 xfs/440 xfs/442
> xfs/517 xfs/535 xfs/538 xfs/551 xfs/552
> Failed 61 of 1071 tests
> 
> Ok, so I did a new no-reflink run as a baseline, because it is a
> while since I've tested DAX at all:
> 
> SECTION       -- xfs_dax_noreflink
> =========================
> Failures: generic/051 generic/068 generic/074 generic/075
> generic/083 generic/112 generic/231 generic/232 generic/269
> generic/270 generic/340 generic/388 generic/461 generic/471
> generic/476 generic/519 generic/560 generic/561 generic/617
> generic/650 generic/656 xfs/011 xfs/013 xfs/017 xfs/073 xfs/297
> xfs/305 xfs/517 xfs/538
> Failed 29 of 1071 tests
> 
> Yeah, there's still lots of warnings from dax_insert_entry() and
> friends like:
> 
> [43262.025815] WARNING: CPU: 9 PID: 1309428 at fs/dax.c:380 dax_insert_entry+0x2ab/0x320
> [43262.028355] Modules linked in:
> [43262.029386] CPU: 9 PID: 1309428 Comm: fsstress Tainted: G W          6.0.0-rc6-dgc+ #1543
> [43262.032168] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> [43262.034840] RIP: 0010:dax_insert_entry+0x2ab/0x320
> [43262.036358] Code: 08 48 83 c4 30 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 58 20 48 8d 53 01 e9 65 ff ff ff 48 8b 58 20 48 8d 53 01 e9 50 ff ff ff <0f> 0b e9 70 ff ff ff 31 f6 4c 89 e7 e8 84 b1 5a 00 eb a4 48 81 e6
> [43262.042255] RSP: 0018:ffffc9000a0cbb78 EFLAGS: 00010002
> [43262.043946] RAX: ffffea0018cd1fc0 RBX: 0000000000000001 RCX: 0000000000000001
> [43262.046233] RDX: ffffea0000000000 RSI: 0000000000000221 RDI: ffffea0018cd2000
> [43262.048518] RBP: 0000000000000011 R08: 0000000000000000 R09: 0000000000000000
> [43262.050762] R10: ffff888241a6d318 R11: 0000000000000001 R12: ffffc9000a0cbc58
> [43262.053020] R13: ffff888241a6d318 R14: ffffc9000a0cbe20 R15: 0000000000000000
> [43262.055309] FS:  00007f8ce25e2b80(0000) GS:ffff8885fec80000(0000) knlGS:0000000000000000
> [43262.057859] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [43262.059713] CR2: 00007f8ce25e1000 CR3: 0000000152141001 CR4: 0000000000060ee0
> [43262.061993] Call Trace:
> [43262.062836]  <TASK>
> [43262.063557]  dax_fault_iter+0x243/0x600
> [43262.064802]  dax_iomap_pte_fault+0x199/0x360
> [43262.066197]  __xfs_filemap_fault+0x1e3/0x2c0
> [43262.067602]  __do_fault+0x31/0x1d0
> [43262.068719]  __handle_mm_fault+0xd6d/0x1650
> [43262.070083]  ? do_mmap+0x348/0x540
> [43262.071200]  handle_mm_fault+0x7a/0x1d0
> [43262.072449]  ? __kvm_handle_async_pf+0x12/0xb0
> [43262.073908]  exc_page_fault+0x1d9/0x810
> [43262.075123]  asm_exc_page_fault+0x22/0x30
> [43262.076413] RIP: 0033:0x7f8ce268bc23
> 
> So it looks to me like DAX is well and truly broken in 6.0-rc6. And,
> yes, I'm running the fixes in mm-hotifxes-stable branch that allow
> xfs/550 to pass.

I have tested these two mode for many times:

xfs_dax mode did failed so many cases.  (If you tested with this "drop" 
patch, some warning around "dax_dedupe_file_range_compare()" won't occur 
any more.)  I think warning around "dax_disassociate_entry()" is a 
problem with concurrency.  Still looking into it.

But xfs_dax_noreflink didn't have so many failure, just 3 in my 
environment: Failures: generic/471 generic/519 xfs/148.  I am thinking 
that did you forget to reformat the TEST_DEV to be non-reflink before 
run the test?  If so it will make sense.


--
Thanks,
Ruan.

> 
> Who is actually testing this DAX code, and what are they actually
> testing on? These are not random failures - I haven't run DAX
> testing since ~5.18, and none of these failures were present on the
> same DAX test VM running the same configuration back then....
> 
> -Dave.