fs/f2fs/segment.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
f2fs_ioc_shutdown(F2FS_GOING_DOWN_NOSYNC) issue_discard_thread
- mnt_want_write_file()
- sb_start_write(SB_FREEZE_WRITE)
- sb_start_intwrite(SB_FREEZE_FS);
- f2fs_stop_checkpoint(sbi, false, : waiting
STOP_CP_REASON_SHUTDOWN);
- f2fs_stop_discard_thread(sbi);
- kthread_stop()
: waiting
- mnt_drop_write_file(filp);
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
fs/f2fs/segment.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 4fd76e867e0a..088b8c48cffa 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1923,7 +1923,9 @@ static int issue_discard_thread(void *data)
continue;
}
- sb_start_intwrite(sbi->sb);
+ /* Avoid the deadlock from F2FS_GOING_DOWN_NOSYNC. */
+ if (!sb_start_intwrite_trylock(sbi->sb))
+ continue;
issued = __issue_discard_cmd(sbi, &dpolicy);
if (issued > 0) {
--
2.44.0.291.gc1ea87d7ee-googOn Tue, 19 Mar 2024 17:14:42 -0700 Jaegeuk Kim <jaegeuk@kernel.org> > f2fs_ioc_shutdown(F2FS_GOING_DOWN_NOSYNC) issue_discard_thread > - mnt_want_write_file() > - sb_start_write(SB_FREEZE_WRITE) __sb_start_write() percpu_down_read() > - sb_start_intwrite(SB_FREEZE_FS); __sb_start_write() percpu_down_read() Given lock acquirers for read on both sides, wtf deadlock are you fixing? > - f2fs_stop_checkpoint(sbi, false, : waiting > STOP_CP_REASON_SHUTDOWN); > - f2fs_stop_discard_thread(sbi); > - kthread_stop() > : waiting > > - mnt_drop_write_file(filp); More important, feel free to add in spin. Reported-by: "Light Hsieh (謝明燈)" <Light.Hsieh@mediatek.com>
On 03/22, Hillf Danton wrote: > On Tue, 19 Mar 2024 17:14:42 -0700 Jaegeuk Kim <jaegeuk@kernel.org> > > f2fs_ioc_shutdown(F2FS_GOING_DOWN_NOSYNC) issue_discard_thread > > - mnt_want_write_file() > > - sb_start_write(SB_FREEZE_WRITE) > __sb_start_write() > percpu_down_read() > > - sb_start_intwrite(SB_FREEZE_FS); > __sb_start_write() > percpu_down_read() > > Given lock acquirers for read on both sides, wtf deadlock are you fixing? Damn. I couldn't think _write uses _read sem. > > > - f2fs_stop_checkpoint(sbi, false, : waiting > > STOP_CP_REASON_SHUTDOWN); > > - f2fs_stop_discard_thread(sbi); > > - kthread_stop() > > : waiting > > > > - mnt_drop_write_file(filp); > > More important, feel free to add in spin. I posted this patch before Light reported. And, in the report, I didn't get this: f2fs_ioc_shutdown() --> freeze_bdev() --> freeze_super() --> sb_wait_write(sb, SB_FREEZE_FS) --> ... ->percpu_down_write(). because f2fs_ioc_shutdown() calls f2fs_stop_discard_thread() after thaw_bdev() like this order. -> freeze_bdev() -> thaw_bdev() -> f2fs_stop_discard_thread() Am I missing something? > > Reported-by: "Light Hsieh (謝明燈)" <Light.Hsieh@mediatek.com>
On Thu, 21 Mar 2024 17:29:03 -0700 Jaegeuk Kim <jaegeuk@kernel.org> > > I posted this patch before Light reported. Yeah, his report's timestamp is 2024-03-20 6:59, nearly 7 hours later, which shows that you constructed the deadlock with nothing to do with his report. > > And, in the report, I didn't get this: > > f2fs_ioc_shutdown() --> freeze_bdev() --> freeze_super() --> sb_wait_write(sb, SB_FREEZE_FS) --> ... ->percpu_down_write(). > > because f2fs_ioc_shutdown() calls f2fs_stop_discard_thread() after thaw_bdev() > like this order. > > -> freeze_bdev() > -> thaw_bdev() > -> f2fs_stop_discard_thread() > > Am I missing something? Light, could you specify to help Jaegeuk understand the deadlock you reported?
On 2024/3/20 8:14, Jaegeuk Kim wrote: > f2fs_ioc_shutdown(F2FS_GOING_DOWN_NOSYNC) issue_discard_thread > - mnt_want_write_file() > - sb_start_write(SB_FREEZE_WRITE) > - sb_start_intwrite(SB_FREEZE_FS); > - f2fs_stop_checkpoint(sbi, false, : waiting > STOP_CP_REASON_SHUTDOWN); > - f2fs_stop_discard_thread(sbi); > - kthread_stop() > : waiting > > - mnt_drop_write_file(filp); > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> Reviewed-by: Chao Yu <chao@kernel.org> Thanks,
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