Hi Chao Yu,
>
>--------- Original Message ---------
>Sender : Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.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+be4a9983e95a5e25c...@syzkaller.appspotmail.com
>Closes:
>https://lore.kernel.org/all/6704d667.050a0220.1e4d62.0081....@google.com
>Signed-off-by: Chao Yu <c...@kernel.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().
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
>
>
>
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