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scsi: sd: use mempool for discard special page

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commit 61cce6f6ee upstream.

When boxes are run near (or to) OOM, we have a problem with the discard
page allocation in sd. If we fail allocating the special page, we return
busy, and it'll get retried. But since ordering is honored for dispatch
requests, we can keep retrying this same IO and failing. Behind that IO
could be requests that want to free memory, but they never get the
chance. This means you get repeated spews of traces like this:

[1201401.625972] Call Trace:
[1201401.631748]  dump_stack+0x4d/0x65
[1201401.639445]  warn_alloc+0xec/0x190
[1201401.647335]  __alloc_pages_slowpath+0xe84/0xf30
[1201401.657722]  ? get_page_from_freelist+0x11b/0xb10
[1201401.668475]  ? __alloc_pages_slowpath+0x2e/0xf30
[1201401.679054]  __alloc_pages_nodemask+0x1f9/0x210
[1201401.689424]  alloc_pages_current+0x8c/0x110
[1201401.699025]  sd_setup_write_same16_cmnd+0x51/0x150
[1201401.709987]  sd_init_command+0x49c/0xb70
[1201401.719029]  scsi_setup_cmnd+0x9c/0x160
[1201401.727877]  scsi_queue_rq+0x4d9/0x610
[1201401.736535]  blk_mq_dispatch_rq_list+0x19a/0x360
[1201401.747113]  blk_mq_sched_dispatch_requests+0xff/0x190
[1201401.758844]  __blk_mq_run_hw_queue+0x95/0xa0
[1201401.768653]  blk_mq_run_work_fn+0x2c/0x30
[1201401.777886]  process_one_work+0x14b/0x400
[1201401.787119]  worker_thread+0x4b/0x470
[1201401.795586]  kthread+0x110/0x150
[1201401.803089]  ? rescuer_thread+0x320/0x320
[1201401.812322]  ? kthread_park+0x90/0x90
[1201401.820787]  ? do_syscall_64+0x53/0x150
[1201401.829635]  ret_from_fork+0x29/0x40

Ensure that the discard page allocation has a mempool backing, so we
know we can make progress.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
[bwh: Backported to 3.16: Only sd_setup_discard_cmnd() does page-allocation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Jens Axboe 2018-12-12 06:46:55 -07:00 • committed by Ben Hutchings
commit eee77673af
1 changed files with 15 additions and 2 deletions
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