[dm-devel] [PATCH 1/3] dm: don't grab target io reference in dm_zone_map_bio
Damien Le Moal
damien.lemoal at opensource.wdc.com
Mon Apr 11 02:19:12 UTC 2022
On 4/11/22 10:04, Ming Lei wrote:
> On Mon, Apr 11, 2022 at 09:50:57AM +0900, Damien Le Moal wrote:
>> On 4/11/22 09:36, Ming Lei wrote:
>>> On Mon, Apr 11, 2022 at 09:18:56AM +0900, Damien Le Moal wrote:
>>>> On 4/9/22 02:12, Ming Lei wrote:
>>>>> dm_zone_map_bio() is only called from __map_bio in which the io's
>>>>> reference is grabbed already, and the reference won't be released
>>>>> until the bio is submitted, so no necessary to do it dm_zone_map_bio
>>>>> any more.
>>>>
>>>> I do not think that this patch is correct. Removing the extra reference on
>>>> the io can lead to problems if the io is completed in the target
>>>> ->map(ti, clone) call or before dm_zone_map_bio_end() is called for the
>>>> DM_MAPIO_SUBMITTED or DM_MAPIO_REMAPPED cases. dm_zone_map_bio_end() needs
>>>
>>> __map_bio():
>>> ...
>>> dm_io_inc_pending(io);
>>> ...
>>> dm_zone_map_bio(tio);
>>> ...
>>
>> dm-crypt (for instance) may terminate the clone bio immediately in its
>> ->map() function context, resulting in the bio_endio()clone) ->
>> clone_endio() -> dm_io_dec_pending() call chain.
>>
>> With that, the io is gone and dm_zone_map_bio_end() will not have a valid
>> reference on the orig bio.
>
> Any target can complete io during ->map. Here looks nothing is special with
> dm-crypt or dm-zone, why does only dm zone need extra reference?
>
> The reference counter is initialized as 1 in init_clone_info(), dm_io_inc_pending()
> in __map_bio() increases it to 2, so after the above call chain you mentioned is done,
> the counter becomes 1. The original bio can't be completed until dm_io_dec_pending()
> in dm_split_and_process_bio() is called.
>
> Or maybe I miss any extra requirement from dm-zone?
Something is wrong... With and without your patch, when I setup a dm-crypt
target on top of a zoned nullblk device, I get:
[ 292.596454] device-mapper: uevent: version 1.0.3
[ 292.602746] device-mapper: ioctl: 4.46.0-ioctl (2022-02-22)
initialised: dm-devel at redhat.com
[ 292.732217] general protection fault, probably for non-canonical
address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN PTI
[ 292.743724] KASAN: null-ptr-deref in range
[0x0000000000000010-0x0000000000000017]
[ 292.751409] CPU: 0 PID: 4259 Comm: systemd-udevd Not tainted
5.18.0-rc2+ #1458
[ 292.758746] Hardware name: Supermicro Super Server/X11DPL-i, BIOS 3.3
02/21/2020
[ 292.766250] RIP: 0010:dm_zone_map_bio+0x146/0x1740 [dm_mod]
[ 292.771938] Code: 00 00 4d 8b 65 10 48 8d 43 28 48 89 44 24 10 49 8d 44
24 10 48 89 c2 48 89 44 24 18 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03
<0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 78 0e 00 00 45 8b 7c 24 10 41
[ 292.790946] RSP: 0018:ffff8883cd847218 EFLAGS: 00010202
[ 292.796260] RAX: dffffc0000000000 RBX: ffff8885c5bcdce8 RCX:
1ffff11034470027
[ 292.803496] RDX: 0000000000000002 RSI: 0000000000000008 RDI:
ffff8885c5bcdc60
[ 292.810732] RBP: 1ffff11079b08e4f R08: ffff8881a23801d8 R09:
ffff8881a238013f
[ 292.817970] R10: ffff88821c594040 R11: 0000000000000001 R12:
0000000000000000
[ 292.825206] R13: ffff8885c5bcdc50 R14: ffff8881a2380000 R15:
ffff8885c5bcdd08
[ 292.832442] FS: 00007fe169b06b40(0000) GS:ffff88880fc00000(0000)
knlGS:0000000000000000
[ 292.840646] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 292.846481] CR2: 00007ffd80a57a38 CR3: 00000004b91b0006 CR4:
00000000007706f0
[ 292.853722] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[ 292.860957] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[ 292.868194] PKRU: 55555554
[ 292.870949] Call Trace:
[ 292.873446] <TASK>
[ 292.875593] ? lock_is_held_type+0xd7/0x130
[ 292.879860] ? dm_set_zones_restrictions+0x8f0/0x8f0 [dm_mod]
[ 292.885718] ? __module_address.part.0+0x25/0x300
[ 292.890509] ? is_module_address+0x43/0x70
[ 292.894674] ? static_obj+0x8a/0xc0
[ 292.898233] __map_bio+0x352/0x740 [dm_mod]
[ 292.902512] dm_submit_bio+0x72f/0x17a0 [dm_mod]
[ 292.907222] ? find_held_lock+0x2c/0x110
[ 292.911217] ? __send_empty_flush+0x2b0/0x2b0 [dm_mod]
[ 292.916459] ? lock_release+0x3b2/0x6f0
[ 292.920368] ? lock_downgrade+0x6d0/0x6d0
[ 292.924458] ? lock_is_held_type+0xd7/0x130
[ 292.928714] __submit_bio+0x12a/0x1f0
[ 292.932450] submit_bio_noacct_nocheck+0x324/0x840
[ 292.937324] ? should_fail_request+0x70/0x70
[ 292.941670] ? rcu_read_lock_sched_held+0x3f/0x70
[ 292.946458] ? submit_bio_noacct+0xfa4/0x1530
[ 292.950888] ? lock_is_held_type+0xd7/0x130
[ 292.957813] mpage_readahead+0x32e/0x4b0
[ 292.964470] ? do_mpage_readpage+0x17c0/0x17c0
[ 292.971661] ? blkdev_write_begin+0x20/0x20
[ 292.978567] ? lock_release+0x3b2/0x6f0
[ 292.985073] ? folio_add_lru+0x217/0x3f0
[ 292.991620] ? lock_downgrade+0x6d0/0x6d0
[ 292.998237] read_pages+0x18c/0x990
[ 293.004308] ? memcg_list_lru_alloc+0x810/0x810
[ 293.011404] ? folio_add_lru+0x238/0x3f0
[ 293.017805] ? file_ra_state_init+0xd0/0xd0
[ 293.024395] ? policy_node+0xbb/0x140
[ 293.030416] page_cache_ra_unbounded+0x258/0x410
[ 293.037376] force_page_cache_ra+0x281/0x400
[ 293.043944] filemap_get_pages+0x25e/0x1290
[ 293.050342] ? __lock_acquire+0x1603/0x6180
[ 293.056654] ? filemap_add_folio+0x140/0x140
[ 293.063002] ? lock_is_held_type+0xd7/0x130
[ 293.069236] filemap_read+0x29e/0x910
[ 293.074927] ? filemap_get_pages+0x1290/0x1290
[ 293.081378] ? __lock_acquire+0x1603/0x6180
[ 293.087558] blkdev_read_iter+0x20c/0x640
[ 293.093529] ? cp_new_stat+0x47a/0x590
[ 293.099190] ? cp_old_stat+0x470/0x470
[ 293.104795] new_sync_read+0x2e4/0x520
[ 293.110362] ? __x64_sys_lseek+0x1d0/0x1d0
[ 293.116269] ? lock_acquire+0x1b2/0x4d0
[ 293.121928] ? find_held_lock+0x2c/0x110
[ 293.127648] vfs_read+0x312/0x430
[ 293.132755] ksys_read+0xf3/0x1d0
[ 293.137863] ? __x64_sys_pwrite64+0x1f0/0x1f0
[ 293.144032] do_syscall_64+0x35/0x80
[ 293.149391] entry_SYSCALL_64_after_hwframe+0x44/0xae
The crash is at: drivers/md/dm-zone.c:499, which is
dm_need_zone_wp_tracking() called from dm_zone_map_bio(). The orig_bio
pointer is invalid. Weird. Investigating.
Also checking why our weekly test runs did not catch this.
--
Damien Le Moal
Western Digital Research
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