fs/f2fs/data.c | 29 +++++++++++++++++++++++++++++ fs/f2fs/f2fs.h | 1 + fs/f2fs/segment.c | 8 ++++++++ 3 files changed, 38 insertions(+)
From: Ruipeng Qi <ruipengqi3@gmail.com>
When the f2fs filesystem space is nearly exhausted, we encounter deadlock
issues as below:
INFO: task A:1890 blocked for more than 120 seconds.
Tainted: G O 6.12.41-g3fe07ddf05ab #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:A state:D stack:0 pid:1890 tgid:1626 ppid:1153 flags:0x00000204
Call trace:
__switch_to+0xf4/0x158
__schedule+0x27c/0x908
schedule+0x3c/0x118
io_schedule+0x44/0x68
folio_wait_bit_common+0x174/0x370
folio_wait_bit+0x20/0x38
folio_wait_writeback+0x54/0xc8
truncate_inode_partial_folio+0x70/0x1e0
truncate_inode_pages_range+0x1b0/0x450
truncate_pagecache+0x54/0x88
f2fs_file_write_iter+0x3e8/0xb80
do_iter_readv_writev+0xf0/0x1e0
vfs_writev+0x138/0x2c8
do_writev+0x88/0x130
__arm64_sys_writev+0x28/0x40
invoke_syscall+0x50/0x120
el0_svc_common.constprop.0+0xc8/0xf0
do_el0_svc+0x24/0x38
el0_svc+0x30/0xf8
el0t_64_sync_handler+0x120/0x130
el0t_64_sync+0x190/0x198
INFO: task kworker/u8:11:2680853 blocked for more than 120 seconds.
Tainted: G O 6.12.41-g3fe07ddf05ab #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:11 state:D stack:0 pid:2680853 tgid:2680853 ppid:2 flags:0x00000208
Workqueue: writeback wb_workfn (flush-254:0)
Call trace:
__switch_to+0xf4/0x158
__schedule+0x27c/0x908
schedule+0x3c/0x118
io_schedule+0x44/0x68
folio_wait_bit_common+0x174/0x370
__filemap_get_folio+0x214/0x348
pagecache_get_page+0x20/0x70
f2fs_get_read_data_page+0x150/0x3e8
f2fs_get_lock_data_page+0x2c/0x160
move_data_page+0x50/0x478
do_garbage_collect+0xd38/0x1528
f2fs_gc+0x240/0x7e0
f2fs_balance_fs+0x1a0/0x208
f2fs_write_single_data_page+0x6e4/0x730
f2fs_write_cache_pages+0x378/0x9b0
f2fs_write_data_pages+0x2e4/0x388
do_writepages+0x8c/0x2c8
__writeback_single_inode+0x4c/0x498
writeback_sb_inodes+0x234/0x4a8
__writeback_inodes_wb+0x58/0x118
wb_writeback+0x2f8/0x3c0
wb_workfn+0x2c4/0x508
process_one_work+0x180/0x408
worker_thread+0x258/0x368
kthread+0x118/0x128
ret_from_fork+0x10/0x200
INFO: task kworker/u8:8:2641297 blocked for more than 120 seconds.
Tainted: G O 6.12.41-g3fe07ddf05ab #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:8 state:D stack:0 pid:2641297 tgid:2641297 ppid:2 flags:0x00000208
Workqueue: writeback wb_workfn (flush-254:0)
Call trace:
__switch_to+0xf4/0x158
__schedule+0x27c/0x908
rt_mutex_schedule+0x30/0x60
__rt_mutex_slowlock_locked.constprop.0+0x460/0x8a8
rwbase_write_lock+0x24c/0x378
down_write+0x1c/0x30
f2fs_balance_fs+0x184/0x208
f2fs_write_inode+0xf4/0x328
__writeback_single_inode+0x370/0x498
writeback_sb_inodes+0x234/0x4a8
__writeback_inodes_wb+0x58/0x118
wb_writeback+0x2f8/0x3c0
wb_workfn+0x2c4/0x508
process_one_work+0x180/0x408
worker_thread+0x258/0x368
kthread+0x118/0x128
ret_from_fork+0x10/0x20
INFO: task B:1902 blocked for more than 120 seconds.
Tainted: G O 6.12.41-g3fe07ddf05ab #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:B state:D stack:0 pid:1902 tgid:1626 ppid:1153 flags:0x0000020c
Call trace:
__switch_to+0xf4/0x158
__schedule+0x27c/0x908
rt_mutex_schedule+0x30/0x60
__rt_mutex_slowlock_locked.constprop.0+0x460/0x8a8
rwbase_write_lock+0x24c/0x378
down_write+0x1c/0x30
f2fs_balance_fs+0x184/0x208
f2fs_map_blocks+0x94c/0x1110
f2fs_file_write_iter+0x228/0xb80
do_iter_readv_writev+0xf0/0x1e0
vfs_writev+0x138/0x2c8
do_writev+0x88/0x130
__arm64_sys_writev+0x28/0x40
invoke_syscall+0x50/0x120
el0_svc_common.constprop.0+0xc8/0xf0
do_el0_svc+0x24/0x38
el0_svc+0x30/0xf8
el0t_64_sync_handler+0x120/0x130
el0t_64_sync+0x190/0x198
INFO: task sync:2769849 blocked for more than 120 seconds.
Tainted: G O 6.12.41-g3fe07ddf05ab #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:sync state:D stack:0 pid:2769849 tgid:2769849 ppid:736 flags:0x0000020c
Call trace:
__switch_to+0xf4/0x158
__schedule+0x27c/0x908
schedule+0x3c/0x118
wb_wait_for_completion+0xb0/0xe8
sync_inodes_sb+0xc8/0x2b0
sync_inodes_one_sb+0x24/0x38
iterate_supers+0xa8/0x138
ksys_sync+0x54/0xc8
__arm64_sys_sync+0x18/0x30
invoke_syscall+0x50/0x120
el0_svc_common.constprop.0+0xc8/0xf0
do_el0_svc+0x24/0x38
el0_svc+0x30/0xf8
el0t_64_sync_handler+0x120/0x130
el0t_64_sync+0x190/0x198
The root cause is a potential deadlock between the following tasks:
kworker/u8:11 Thread A
- f2fs_write_single_data_page
- f2fs_do_write_data_page
- folio_start_writeback(X)
- f2fs_outplace_write_data
- bio_add_folio(X)
- folio_unlock(X)
- truncate_inode_pages_range
- __filemap_get_folio(X, FGP_LOCK)
- truncate_inode_partial_folio(X)
- folio_wait_writeback(X)
- f2fs_balance_fs
- f2fs_gc
- do_garbage_collect
- move_data_page
- f2fs_get_lock_data_page
- __filemap_get_folio(X, FGP_LOCK)
Both threads try to access folio X. Thread A holds the lock but waits
for writeback, while kworker waits for the lock. This causes a deadlock.
Other threads also enter D state, waiting for locks such as gc_lock and
writepages.
OPU/IPU DATA folio are all affected by this issue. To avoid such
potential deadlocks, always commit these cached folios before
triggering f2fs_gc() in f2fs_balance_fs().
v2:
- Commit cached OPU/IPU folios, not just OPU folios as in v1.
v3:
- Fixed minor grammatical issues
- Add comment on lockless list_empty() to explain why it is safe
without holding bio_list_lock
Suggested-by: Chao <chao@kernel.org>
Signed-off-by: Ruipeng Qi <ruipengqi3@gmail.com>
---
fs/f2fs/data.c | 29 +++++++++++++++++++++++++++++
fs/f2fs/f2fs.h | 1 +
fs/f2fs/segment.c | 8 ++++++++
3 files changed, 38 insertions(+)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 338df7a2aea6..98e3863b9b54 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -939,6 +939,35 @@ void f2fs_submit_merged_ipu_write(struct f2fs_sb_info *sbi,
}
}
+void f2fs_submit_all_merged_ipu_writes(struct f2fs_sb_info *sbi)
+{
+ struct bio_entry *be, *tmp;
+ struct f2fs_bio_info *io;
+ enum temp_type temp;
+
+ for (temp = HOT; temp < NR_TEMP_TYPE; temp++) {
+ LIST_HEAD(list);
+
+ io = sbi->write_io[DATA] + temp;
+
+ /* A lockless list_empty() check is safe here: any bios from
+ * other kworkers that we miss will be submitted by those
+ * kworkers accordingly.
+ */
+ if (list_empty(&io->bio_list))
+ continue;
+
+ f2fs_down_write(&io->bio_list_lock);
+ list_splice_init(&io->bio_list, &list);
+ f2fs_up_write(&io->bio_list_lock);
+
+ list_for_each_entry_safe(be, tmp, &list, list) {
+ f2fs_submit_write_bio(sbi, be->bio, DATA);
+ del_bio_entry(be);
+ }
+ }
+}
+
int f2fs_merge_page_bio(struct f2fs_io_info *fio)
{
struct bio *bio = *fio->bio;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index bb34e864d0ef..e9038ab1b2bd 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4148,6 +4148,7 @@ void f2fs_submit_merged_write_folio(struct f2fs_sb_info *sbi,
struct folio *folio, enum page_type type);
void f2fs_submit_merged_ipu_write(struct f2fs_sb_info *sbi,
struct bio **bio, struct folio *folio);
+void f2fs_submit_all_merged_ipu_writes(struct f2fs_sb_info *sbi);
void f2fs_flush_merged_writes(struct f2fs_sb_info *sbi);
int f2fs_submit_page_bio(struct f2fs_io_info *fio);
int f2fs_merge_page_bio(struct f2fs_io_info *fio);
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 6a97fe76712b..b57d36f66681 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -462,6 +462,14 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
.should_migrate_blocks = false,
.err_gc_skipped = false,
.nr_free_secs = 1 };
+
+ /*
+ * Submit all cached OPU/IPU DATA bios before triggering
+ * foreground GC to avoid potential deadlocks.
+ */
+ f2fs_submit_merged_write(sbi, DATA);
+ f2fs_submit_all_merged_ipu_writes(sbi);
+
f2fs_down_write_trace(&sbi->gc_lock, &gc_control.lc);
stat_inc_gc_call_count(sbi, FOREGROUND);
f2fs_gc(sbi, &gc_control);
--
2.25.1On 5/2/26 20:41, ruipengqi wrote: > From: Ruipeng Qi <ruipengqi3@gmail.com> > > When the f2fs filesystem space is nearly exhausted, we encounter deadlock > issues as below: > > INFO: task A:1890 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:A state:D stack:0 pid:1890 tgid:1626 ppid:1153 flags:0x00000204 > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > schedule+0x3c/0x118 > io_schedule+0x44/0x68 > folio_wait_bit_common+0x174/0x370 > folio_wait_bit+0x20/0x38 > folio_wait_writeback+0x54/0xc8 > truncate_inode_partial_folio+0x70/0x1e0 > truncate_inode_pages_range+0x1b0/0x450 > truncate_pagecache+0x54/0x88 > f2fs_file_write_iter+0x3e8/0xb80 > do_iter_readv_writev+0xf0/0x1e0 > vfs_writev+0x138/0x2c8 > do_writev+0x88/0x130 > __arm64_sys_writev+0x28/0x40 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0xc8/0xf0 > do_el0_svc+0x24/0x38 > el0_svc+0x30/0xf8 > el0t_64_sync_handler+0x120/0x130 > el0t_64_sync+0x190/0x198 > > INFO: task kworker/u8:11:2680853 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:kworker/u8:11 state:D stack:0 pid:2680853 tgid:2680853 ppid:2 flags:0x00000208 > Workqueue: writeback wb_workfn (flush-254:0) > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > schedule+0x3c/0x118 > io_schedule+0x44/0x68 > folio_wait_bit_common+0x174/0x370 > __filemap_get_folio+0x214/0x348 > pagecache_get_page+0x20/0x70 > f2fs_get_read_data_page+0x150/0x3e8 > f2fs_get_lock_data_page+0x2c/0x160 > move_data_page+0x50/0x478 > do_garbage_collect+0xd38/0x1528 > f2fs_gc+0x240/0x7e0 > f2fs_balance_fs+0x1a0/0x208 > f2fs_write_single_data_page+0x6e4/0x730 > f2fs_write_cache_pages+0x378/0x9b0 > f2fs_write_data_pages+0x2e4/0x388 > do_writepages+0x8c/0x2c8 > __writeback_single_inode+0x4c/0x498 > writeback_sb_inodes+0x234/0x4a8 > __writeback_inodes_wb+0x58/0x118 > wb_writeback+0x2f8/0x3c0 > wb_workfn+0x2c4/0x508 > process_one_work+0x180/0x408 > worker_thread+0x258/0x368 > kthread+0x118/0x128 > ret_from_fork+0x10/0x200 > > INFO: task kworker/u8:8:2641297 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:kworker/u8:8 state:D stack:0 pid:2641297 tgid:2641297 ppid:2 flags:0x00000208 > Workqueue: writeback wb_workfn (flush-254:0) > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > rt_mutex_schedule+0x30/0x60 > __rt_mutex_slowlock_locked.constprop.0+0x460/0x8a8 > rwbase_write_lock+0x24c/0x378 > down_write+0x1c/0x30 > f2fs_balance_fs+0x184/0x208 > f2fs_write_inode+0xf4/0x328 > __writeback_single_inode+0x370/0x498 > writeback_sb_inodes+0x234/0x4a8 > __writeback_inodes_wb+0x58/0x118 > wb_writeback+0x2f8/0x3c0 > wb_workfn+0x2c4/0x508 > process_one_work+0x180/0x408 > worker_thread+0x258/0x368 > kthread+0x118/0x128 > ret_from_fork+0x10/0x20 > > INFO: task B:1902 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:B state:D stack:0 pid:1902 tgid:1626 ppid:1153 flags:0x0000020c > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > rt_mutex_schedule+0x30/0x60 > __rt_mutex_slowlock_locked.constprop.0+0x460/0x8a8 > rwbase_write_lock+0x24c/0x378 > down_write+0x1c/0x30 > f2fs_balance_fs+0x184/0x208 > f2fs_map_blocks+0x94c/0x1110 > f2fs_file_write_iter+0x228/0xb80 > do_iter_readv_writev+0xf0/0x1e0 > vfs_writev+0x138/0x2c8 > do_writev+0x88/0x130 > __arm64_sys_writev+0x28/0x40 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0xc8/0xf0 > do_el0_svc+0x24/0x38 > el0_svc+0x30/0xf8 > el0t_64_sync_handler+0x120/0x130 > el0t_64_sync+0x190/0x198 > > INFO: task sync:2769849 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:sync state:D stack:0 pid:2769849 tgid:2769849 ppid:736 flags:0x0000020c > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > schedule+0x3c/0x118 > wb_wait_for_completion+0xb0/0xe8 > sync_inodes_sb+0xc8/0x2b0 > sync_inodes_one_sb+0x24/0x38 > iterate_supers+0xa8/0x138 > ksys_sync+0x54/0xc8 > __arm64_sys_sync+0x18/0x30 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0xc8/0xf0 > do_el0_svc+0x24/0x38 > el0_svc+0x30/0xf8 > el0t_64_sync_handler+0x120/0x130 > el0t_64_sync+0x190/0x198 > > The root cause is a potential deadlock between the following tasks: > > kworker/u8:11 Thread A > - f2fs_write_single_data_page > - f2fs_do_write_data_page > - folio_start_writeback(X) > - f2fs_outplace_write_data > - bio_add_folio(X) > - folio_unlock(X) > - truncate_inode_pages_range > - __filemap_get_folio(X, FGP_LOCK) > - truncate_inode_partial_folio(X) > - folio_wait_writeback(X) > - f2fs_balance_fs > - f2fs_gc > - do_garbage_collect > - move_data_page > - f2fs_get_lock_data_page > - __filemap_get_folio(X, FGP_LOCK) > > Both threads try to access folio X. Thread A holds the lock but waits > for writeback, while kworker waits for the lock. This causes a deadlock. > > Other threads also enter D state, waiting for locks such as gc_lock and > writepages. > > OPU/IPU DATA folio are all affected by this issue. To avoid such > potential deadlocks, always commit these cached folios before > triggering f2fs_gc() in f2fs_balance_fs(). > > v2: > - Commit cached OPU/IPU folios, not just OPU folios as in v1. > > v3: > - Fixed minor grammatical issues > - Add comment on lockless list_empty() to explain why it is safe > without holding bio_list_lock > > Suggested-by: Chao <chao@kernel.org> Chao Yu <chao@kernel.org>, :) > Signed-off-by: Ruipeng Qi <ruipengqi3@gmail.com> Reviewed-by: Chao Yu <chao@kernel.org> Thanks,
On 5/3/2026 5:47 PM, Chao Yu wrote: > On 5/2/26 20:41, ruipengqi wrote: >> From: Ruipeng Qi <ruipengqi3@gmail.com> >> >> When the f2fs filesystem space is nearly exhausted, we encounter >> deadlock >> issues as below: >> >> INFO: task A:1890 blocked for more than 120 seconds. >> Tainted: G O 6.12.41-g3fe07ddf05ab #1 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this >> message. >> task:A state:D stack:0 pid:1890 tgid:1626 ppid:1153 >> flags:0x00000204 >> Call trace: >> __switch_to+0xf4/0x158 >> __schedule+0x27c/0x908 >> schedule+0x3c/0x118 >> io_schedule+0x44/0x68 >> folio_wait_bit_common+0x174/0x370 >> folio_wait_bit+0x20/0x38 >> folio_wait_writeback+0x54/0xc8 >> truncate_inode_partial_folio+0x70/0x1e0 >> truncate_inode_pages_range+0x1b0/0x450 >> truncate_pagecache+0x54/0x88 >> f2fs_file_write_iter+0x3e8/0xb80 >> do_iter_readv_writev+0xf0/0x1e0 >> vfs_writev+0x138/0x2c8 >> do_writev+0x88/0x130 >> __arm64_sys_writev+0x28/0x40 >> invoke_syscall+0x50/0x120 >> el0_svc_common.constprop.0+0xc8/0xf0 >> do_el0_svc+0x24/0x38 >> el0_svc+0x30/0xf8 >> el0t_64_sync_handler+0x120/0x130 >> el0t_64_sync+0x190/0x198 >> >> INFO: task kworker/u8:11:2680853 blocked for more than 120 seconds. >> Tainted: G O 6.12.41-g3fe07ddf05ab #1 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this >> message. >> task:kworker/u8:11 state:D stack:0 pid:2680853 tgid:2680853 >> ppid:2 flags:0x00000208 >> Workqueue: writeback wb_workfn (flush-254:0) >> Call trace: >> __switch_to+0xf4/0x158 >> __schedule+0x27c/0x908 >> schedule+0x3c/0x118 >> io_schedule+0x44/0x68 >> folio_wait_bit_common+0x174/0x370 >> __filemap_get_folio+0x214/0x348 >> pagecache_get_page+0x20/0x70 >> f2fs_get_read_data_page+0x150/0x3e8 >> f2fs_get_lock_data_page+0x2c/0x160 >> move_data_page+0x50/0x478 >> do_garbage_collect+0xd38/0x1528 >> f2fs_gc+0x240/0x7e0 >> f2fs_balance_fs+0x1a0/0x208 >> f2fs_write_single_data_page+0x6e4/0x730 >> f2fs_write_cache_pages+0x378/0x9b0 >> f2fs_write_data_pages+0x2e4/0x388 >> do_writepages+0x8c/0x2c8 >> __writeback_single_inode+0x4c/0x498 >> writeback_sb_inodes+0x234/0x4a8 >> __writeback_inodes_wb+0x58/0x118 >> wb_writeback+0x2f8/0x3c0 >> wb_workfn+0x2c4/0x508 >> process_one_work+0x180/0x408 >> worker_thread+0x258/0x368 >> kthread+0x118/0x128 >> ret_from_fork+0x10/0x200 >> >> INFO: task kworker/u8:8:2641297 blocked for more than 120 seconds. >> Tainted: G O 6.12.41-g3fe07ddf05ab #1 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this >> message. >> task:kworker/u8:8 state:D stack:0 pid:2641297 tgid:2641297 >> ppid:2 flags:0x00000208 >> Workqueue: writeback wb_workfn (flush-254:0) >> Call trace: >> __switch_to+0xf4/0x158 >> __schedule+0x27c/0x908 >> rt_mutex_schedule+0x30/0x60 >> __rt_mutex_slowlock_locked.constprop.0+0x460/0x8a8 >> rwbase_write_lock+0x24c/0x378 >> down_write+0x1c/0x30 >> f2fs_balance_fs+0x184/0x208 >> f2fs_write_inode+0xf4/0x328 >> __writeback_single_inode+0x370/0x498 >> writeback_sb_inodes+0x234/0x4a8 >> __writeback_inodes_wb+0x58/0x118 >> wb_writeback+0x2f8/0x3c0 >> wb_workfn+0x2c4/0x508 >> process_one_work+0x180/0x408 >> worker_thread+0x258/0x368 >> kthread+0x118/0x128 >> ret_from_fork+0x10/0x20 >> >> INFO: task B:1902 blocked for more than 120 seconds. >> Tainted: G O 6.12.41-g3fe07ddf05ab #1 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this >> message. >> task:B state:D stack:0 pid:1902 tgid:1626 ppid:1153 >> flags:0x0000020c >> Call trace: >> __switch_to+0xf4/0x158 >> __schedule+0x27c/0x908 >> rt_mutex_schedule+0x30/0x60 >> __rt_mutex_slowlock_locked.constprop.0+0x460/0x8a8 >> rwbase_write_lock+0x24c/0x378 >> down_write+0x1c/0x30 >> f2fs_balance_fs+0x184/0x208 >> f2fs_map_blocks+0x94c/0x1110 >> f2fs_file_write_iter+0x228/0xb80 >> do_iter_readv_writev+0xf0/0x1e0 >> vfs_writev+0x138/0x2c8 >> do_writev+0x88/0x130 >> __arm64_sys_writev+0x28/0x40 >> invoke_syscall+0x50/0x120 >> el0_svc_common.constprop.0+0xc8/0xf0 >> do_el0_svc+0x24/0x38 >> el0_svc+0x30/0xf8 >> el0t_64_sync_handler+0x120/0x130 >> el0t_64_sync+0x190/0x198 >> >> INFO: task sync:2769849 blocked for more than 120 seconds. >> Tainted: G O 6.12.41-g3fe07ddf05ab #1 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this >> message. >> task:sync state:D stack:0 pid:2769849 tgid:2769849 >> ppid:736 flags:0x0000020c >> Call trace: >> __switch_to+0xf4/0x158 >> __schedule+0x27c/0x908 >> schedule+0x3c/0x118 >> wb_wait_for_completion+0xb0/0xe8 >> sync_inodes_sb+0xc8/0x2b0 >> sync_inodes_one_sb+0x24/0x38 >> iterate_supers+0xa8/0x138 >> ksys_sync+0x54/0xc8 >> __arm64_sys_sync+0x18/0x30 >> invoke_syscall+0x50/0x120 >> el0_svc_common.constprop.0+0xc8/0xf0 >> do_el0_svc+0x24/0x38 >> el0_svc+0x30/0xf8 >> el0t_64_sync_handler+0x120/0x130 >> el0t_64_sync+0x190/0x198 >> >> The root cause is a potential deadlock between the following tasks: >> >> kworker/u8:11 Thread A >> - f2fs_write_single_data_page >> - f2fs_do_write_data_page >> - folio_start_writeback(X) >> - f2fs_outplace_write_data >> - bio_add_folio(X) >> - folio_unlock(X) >> - truncate_inode_pages_range >> - __filemap_get_folio(X, FGP_LOCK) >> - truncate_inode_partial_folio(X) >> - folio_wait_writeback(X) >> - f2fs_balance_fs >> - f2fs_gc >> - do_garbage_collect >> - move_data_page >> - f2fs_get_lock_data_page >> - __filemap_get_folio(X, FGP_LOCK) >> >> Both threads try to access folio X. Thread A holds the lock but waits >> for writeback, while kworker waits for the lock. This causes a deadlock. >> >> Other threads also enter D state, waiting for locks such as gc_lock and >> writepages. >> >> OPU/IPU DATA folio are all affected by this issue. To avoid such >> potential deadlocks, always commit these cached folios before >> triggering f2fs_gc() in f2fs_balance_fs(). >> >> v2: >> - Commit cached OPU/IPU folios, not just OPU folios as in v1. >> >> v3: >> - Fixed minor grammatical issues >> - Add comment on lockless list_empty() to explain why it is safe >> without holding bio_list_lock >> >> Suggested-by: Chao <chao@kernel.org> > > Chao Yu <chao@kernel.org>, :) > >> Signed-off-by: Ruipeng Qi <ruipengqi3@gmail.com> > > Reviewed-by: Chao Yu <chao@kernel.org> > > Thanks, Hi Jaegeuk, Chao, Gentle ping. This patch has been discussed for about a month and already got Reviewed-by from Chao. Could you please pick up this patch when you have time? Thanks, Ruipeng
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