Re: [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock in f2fs_record_stop_reason()
From: Chao Yu
Date: Tue Oct 22 2024 - 04:29:57 EST
On 2024/10/22 16:22, Daejun Park wrote:
Hi Chao Yu,
--------- Original Message ---------
Sender : Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/6704d667.050a0220.1e4d62.0081.GAE@xxxxxxxxxx
Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
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
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