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Message-ID: <0c28ce02-c1da-4259-b2e6-221693c2144f@kernel.org>
Date: Tue, 22 Oct 2024 16:29:28 +0800
From: Chao Yu <chao@...nel.org>
To: daejun7.park@...sung.com, "jaegeuk@...nel.org" <jaegeuk@...nel.org>
Cc: Chao Yu <chao@...nel.org>,
"syzbot+be4a9983e95a5e25c8d3@...kaller.appspotmail.com"
<syzbot+be4a9983e95a5e25c8d3@...kaller.appspotmail.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-f2fs-devel@...ts.sourceforge.net"
<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock in
f2fs_record_stop_reason()
On 2024/10/22 16:22, Daejun Park wrote:
> Hi Chao Yu,
>
>
>>
>> --------- Original Message ---------
>> Sender : Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@...ts.sourceforge.net>
>> Date : 2024-10-22 15:21 (GMT+9)
>> Title : [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock in f2fs_record_stop_reason()
>>
>> syzbot reports deadlock issue of f2fs as below:
>>
>> ======================================================
>> WARNING: possible circular locking dependency detected
>> 6.12.0-rc3-syzkaller-00087-gc964ced77262 #0 Not tainted
>> ------------------------------------------------------
>> kswapd0/79 is trying to acquire lock:
>> ffff888011824088 (&sbi->sb_lock){++++}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2199 [inline]
>> ffff888011824088 (&sbi->sb_lock){++++}-{3:3}, at: f2fs_record_stop_reason+0x52/0x1d0 fs/f2fs/super.c:4068
>>
>> but task is already holding lock:
>> ffff88804bd92610 (sb_internal#2){.+.+}-{0:0}, at: f2fs_evict_inode+0x662/0x15c0 fs/f2fs/inode.c:842
>>
>> which lock already depends on the new lock.
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #2 (sb_internal#2){.+.+}-{0:0}:
>> lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
>> percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
>> __sb_start_write include/linux/fs.h:1716 [inline]
>> sb_start_intwrite+0x4d/0x1c0 include/linux/fs.h:1899
>> f2fs_evict_inode+0x662/0x15c0 fs/f2fs/inode.c:842
>> evict+0x4e8/0x9b0 fs/inode.c:725
>> f2fs_evict_inode+0x1a4/0x15c0 fs/f2fs/inode.c:807
>> evict+0x4e8/0x9b0 fs/inode.c:725
>> dispose_list fs/inode.c:774 [inline]
>> prune_icache_sb+0x239/0x2f0 fs/inode.c:963
>> super_cache_scan+0x38c/0x4b0 fs/super.c:223
>> do_shrink_slab+0x701/0x1160 mm/shrinker.c:435
>> shrink_slab+0x1093/0x14d0 mm/shrinker.c:662
>> shrink_one+0x43b/0x850 mm/vmscan.c:4818
>> shrink_many mm/vmscan.c:4879 [inline]
>> lru_gen_shrink_node mm/vmscan.c:4957 [inline]
>> shrink_node+0x3799/0x3de0 mm/vmscan.c:5937
>> kswapd_shrink_node mm/vmscan.c:6765 [inline]
>> balance_pgdat mm/vmscan.c:6957 [inline]
>> kswapd+0x1ca3/0x3700 mm/vmscan.c:7226
>> kthread+0x2f0/0x390 kernel/kthread.c:389
>> ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>>
>> -> #1 (fs_reclaim){+.+.}-{0:0}:
>> lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
>> __fs_reclaim_acquire mm/page_alloc.c:3834 [inline]
>> fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3848
>> might_alloc include/linux/sched/mm.h:318 [inline]
>> prepare_alloc_pages+0x147/0x5b0 mm/page_alloc.c:4493
>> __alloc_pages_noprof+0x16f/0x710 mm/page_alloc.c:4722
>> alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
>> alloc_pages_noprof mm/mempolicy.c:2345 [inline]
>> folio_alloc_noprof+0x128/0x180 mm/mempolicy.c:2352
>> filemap_alloc_folio_noprof+0xdf/0x500 mm/filemap.c:1010
>> do_read_cache_folio+0x2eb/0x850 mm/filemap.c:3787
>> read_mapping_folio include/linux/pagemap.h:1011 [inline]
>> f2fs_commit_super+0x3c0/0x7d0 fs/f2fs/super.c:4032
>> f2fs_record_stop_reason+0x13b/0x1d0 fs/f2fs/super.c:4079
>> f2fs_handle_critical_error+0x2ac/0x5c0 fs/f2fs/super.c:4174
>> f2fs_write_inode+0x35f/0x4d0 fs/f2fs/inode.c:785
>> write_inode fs/fs-writeback.c:1503 [inline]
>> __writeback_single_inode+0x711/0x10d0 fs/fs-writeback.c:1723
>> writeback_single_inode+0x1f3/0x660 fs/fs-writeback.c:1779
>> sync_inode_metadata+0xc4/0x120 fs/fs-writeback.c:2849
>> f2fs_release_file+0xa8/0x100 fs/f2fs/file.c:1941
>> __fput+0x23f/0x880 fs/file_table.c:431
>> task_work_run+0x24f/0x310 kernel/task_work.c:228
>> resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
>> exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
>> exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
>> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
>> syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:218
>> do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>
>> -> #0 (&sbi->sb_lock){++++}-{3:3}:
>> check_prev_add kernel/locking/lockdep.c:3161 [inline]
>> check_prevs_add kernel/locking/lockdep.c:3280 [inline]
>> validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
>> __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
>> lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
>> down_write+0x99/0x220 kernel/locking/rwsem.c:1577
>> f2fs_down_write fs/f2fs/f2fs.h:2199 [inline]
>> f2fs_record_stop_reason+0x52/0x1d0 fs/f2fs/super.c:4068
>> f2fs_handle_critical_error+0x2ac/0x5c0 fs/f2fs/super.c:4174
>> f2fs_evict_inode+0xa61/0x15c0 fs/f2fs/inode.c:883
>> evict+0x4e8/0x9b0 fs/inode.c:725
>> f2fs_evict_inode+0x1a4/0x15c0 fs/f2fs/inode.c:807
>> evict+0x4e8/0x9b0 fs/inode.c:725
>> dispose_list fs/inode.c:774 [inline]
>> prune_icache_sb+0x239/0x2f0 fs/inode.c:963
>> super_cache_scan+0x38c/0x4b0 fs/super.c:223
>> do_shrink_slab+0x701/0x1160 mm/shrinker.c:435
>> shrink_slab+0x1093/0x14d0 mm/shrinker.c:662
>> shrink_one+0x43b/0x850 mm/vmscan.c:4818
>> shrink_many mm/vmscan.c:4879 [inline]
>> lru_gen_shrink_node mm/vmscan.c:4957 [inline]
>> shrink_node+0x3799/0x3de0 mm/vmscan.c:5937
>> kswapd_shrink_node mm/vmscan.c:6765 [inline]
>> balance_pgdat mm/vmscan.c:6957 [inline]
>> kswapd+0x1ca3/0x3700 mm/vmscan.c:7226
>> kthread+0x2f0/0x390 kernel/kthread.c:389
>> ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>>
>> other info that might help us debug this:
>>
>> Chain exists of:
>> &sbi->sb_lock --> fs_reclaim --> sb_internal#2
>>
>> Possible unsafe locking scenario:
>>
>> CPU0 CPU1
>> ---- ----
>> rlock(sb_internal#2);
>> lock(fs_reclaim);
>> lock(sb_internal#2);
>> lock(&sbi->sb_lock);
>>
>> Root cause is there will be potential deadlock in between
>> below tasks:
>>
>> Thread A Kswapd
>> - f2fs_ioc_commit_atomic_write
>> - mnt_want_write_file -- down_read lock A
>> - balance_pgdat
>> - __fs_reclaim_acquire -- lock B
>> - shrink_node
>> - prune_icache_sb
>> - dispose_list
>> - f2fs_evict_inode
>> - sb_start_intwrite -- down_read lock A
>> - f2fs_do_sync_file
>> - f2fs_write_inode
>> - f2fs_handle_critical_error
>> - f2fs_record_stop_reason
>> - f2fs_commit_super
>> - read_mapping_folio
>> - filemap_alloc_folio_noprof
>> - fs_reclaim_acquire -- lock B
>>
>> Both threads try to acquire read lock of lock A, then its upcoming write
>> lock grabber will trigger deadlock.
>>
>> Let's always create an asynchronous task in f2fs_handle_critical_error()
>> rather than calling f2fs_record_stop_reason() synchronously to avoid
>> this potential deadlock issue.
>>
>> Fixes: b62e71be2110 ("f2fs: support errors=remount-rocontinuepanic mountoption")
>> Reported-by: syzbot+be4a9983e95a5e25c8d3@...kaller.appspotmail.com
>> Closes: https://lore.kernel.org/all/6704d667.050a0220.1e4d62.0081.GAE@google.com
>> Signed-off-by: Chao Yu <chao@...nel.org>
>> ---
>> fs/f2fs/super.c 10 ++++++----
>> 1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index 9325d8dc7f7d..21d6fb60171a 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -4174,10 +4174,12 @@ void f2fs_handle_critical_error(struct f2fs_sb_info *sbi, unsigned char reason,
>> if (!f2fs_hw_is_readonly(sbi)) {
>> save_stop_reason(sbi, reason);
>>
>> - if (irq_context && !shutdown)
>
> I think the irq_context parameter can be removed from f2fs_handle_critical_error().
Ah, correct, let me update it in v2, thank you!
Thanks,
>
> Thanks,
> Daejun
>
>> - schedule_work(&sbi->s_error_work);
>> - else
>> - f2fs_record_stop_reason(sbi);
>> + /*
>> + * always create an asynchronous task to record stop_reason
>> + * in order to avoid potential deadlock when running into
>> + * f2fs_record_stop_reason() synchronously.
>> + */
>> + schedule_work(&sbi->s_error_work);
>> }
>>
>> /*
>> --
>> 2.40.1
>>
>>
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@...ts.sourceforge.net
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