As Ju Hyung Park reported:
"When 'fstrim' is called for manual trim, a BUG() can be triggered
randomly with this patch.
I'm seeing this issue on both x86 Desktop and arm64 Android phone.
On x86 Desktop, this was caused during Ubuntu boot-up. I have a
cronjob installed which calls 'fstrim -v /' during boot. On arm64
Android, this was caused during GC looping with 1ms gc_min_sleep_time
& gc_max_sleep_time."
Root cause of this issue is that f2fs_wait_discard_bios can only be
used by f2fs_put_super, because during put_super there must be no
other referrers, so it can ignore discard entry's reference count
when removing the entry, otherwise in other caller we will hit bug_on
in __remove_discard_cmd as there may be other issuer added reference
count in discard entry.
Thread A Thread B
- issue_discard_thread
- f2fs_ioc_fitrim
- f2fs_trim_fs
- f2fs_wait_discard_bios
- __issue_discard_cmd
- __submit_discard_cmd
- __wait_discard_cmd
- dc->ref++
- __wait_one_discard_bio
- __wait_discard_cmd
- __remove_discard_cmd
- f2fs_bug_on(sbi, dc->ref)
Fixes: 969d1b180d
Reported-by: Ju Hyung Park <qkrwngud825@gmail.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
638164a271