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From: Nhat Pham <nphamcs@gmail.com>
Date: Fri, 22 Mar 2024 10:09:56 -0700
Message-ID: <CAKEwX=Pnr1HZipHTqnvMruh21uO7UXDP67nAZ5s_WrwgWkNpzg@mail.gmail.com>
Subject: Re: [PATCH] mm: zswap: fix writeback shinker GFP_NOIO/GFP_NOFS recursion
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, Kent Overstreet <kent.overstreet@linux.dev>, 
	Chengming Zhou <zhouchengming@bytedance.com>, Yosry Ahmed <yosryahmed@google.com>, linux-mm@kvack.org, 
	linux-kernel@vger.kernel.org, stable@vger.kernel.org
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On Thu, Mar 21, 2024 at 11:25=E2=80=AFAM Johannes Weiner <hannes@cmpxchg.or=
g> wrote:
>
> Kent forwards this bug report of zswap re-entering the block layer
> from an IO request allocation and locking up:
>
> [10264.128242] sysrq: Show Blocked State
> [10264.128268] task:kworker/20:0H   state:D stack:0     pid:143   tgid:14=
3   ppid:2      flags:0x00004000
> [10264.128271] Workqueue: bcachefs_io btree_write_submit [bcachefs]
> [10264.128295] Call Trace:
> [10264.128295]  <TASK>
> [10264.128297]  __schedule+0x3e6/0x1520
> [10264.128303]  schedule+0x32/0xd0
> [10264.128304]  schedule_timeout+0x98/0x160
> [10264.128308]  io_schedule_timeout+0x50/0x80
> [10264.128309]  wait_for_completion_io_timeout+0x7f/0x180
> [10264.128310]  submit_bio_wait+0x78/0xb0
> [10264.128313]  swap_writepage_bdev_sync+0xf6/0x150
> [10264.128317]  zswap_writeback_entry+0xf2/0x180
> [10264.128319]  shrink_memcg_cb+0xe7/0x2f0
> [10264.128322]  __list_lru_walk_one+0xb9/0x1d0
> [10264.128325]  list_lru_walk_one+0x5d/0x90
> [10264.128326]  zswap_shrinker_scan+0xc4/0x130
> [10264.128327]  do_shrink_slab+0x13f/0x360
> [10264.128328]  shrink_slab+0x28e/0x3c0
> [10264.128329]  shrink_one+0x123/0x1b0
> [10264.128331]  shrink_node+0x97e/0xbc0
> [10264.128332]  do_try_to_free_pages+0xe7/0x5b0
> [10264.128333]  try_to_free_pages+0xe1/0x200
> [10264.128334]  __alloc_pages_slowpath.constprop.0+0x343/0xde0
> [10264.128337]  __alloc_pages+0x32d/0x350
> [10264.128338]  allocate_slab+0x400/0x460
> [10264.128339]  ___slab_alloc+0x40d/0xa40
> [10264.128345]  kmem_cache_alloc+0x2e7/0x330
> [10264.128348]  mempool_alloc+0x86/0x1b0
> [10264.128349]  bio_alloc_bioset+0x200/0x4f0
> [10264.128352]  bio_alloc_clone+0x23/0x60
> [10264.128354]  alloc_io+0x26/0xf0 [dm_mod 7e9e6b44df4927f93fb3e4b5c78276=
7396f58382]
> [10264.128361]  dm_submit_bio+0xb8/0x580 [dm_mod 7e9e6b44df4927f93fb3e4b5=
c782767396f58382]
> [10264.128366]  __submit_bio+0xb0/0x170
> [10264.128367]  submit_bio_noacct_nocheck+0x159/0x370
> [10264.128368]  bch2_submit_wbio_replicas+0x21c/0x3a0 [bcachefs 85f1b9a7a=
824f272eff794653a06dde1a94439f2]
> [10264.128391]  btree_write_submit+0x1cf/0x220 [bcachefs 85f1b9a7a824f272=
eff794653a06dde1a94439f2]
> [10264.128406]  process_one_work+0x178/0x350
> [10264.128408]  worker_thread+0x30f/0x450
> [10264.128409]  kthread+0xe5/0x120
>
> The zswap shrinker resumes the swap_writepage()s that were intercepted
> by the zswap store. This will enter the block layer, and may even
> enter the filesystem depending on the swap backing file.
>
> Make it respect GFP_NOIO and GFP_NOFS.
>
> Link: https://lore.kernel.org/linux-mm/rc4pk2r42oyvjo4dc62z6sovquyllq56i5=
cdgcaqbd7wy3hfzr@n4nbxido3fme/
> Reported-by: Kent Overstreet <kent.overstreet@linux.dev>
> Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure")
> Cc: stable@vger.kernel.org      [v6.8]
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Nhat Pham <nphamcs@gmail.com>