On Sat, Jun 8, 2024 at 5:36 AM Chao Yu <c...@kernel.org> wrote:
>
> On 2024/6/6 17:52, Chao Yu wrote:
> > After commit 261eeb9c1585 ("f2fs: introduce checkpoint_merge mount
> > option"), checkpoint can be triggered in background thread, it missed
> > to cover f2fs inner checkpoint operation w/ sb_{start,end}_intwrite(),
> > fix it.
>
> It needs to use sb_start_intwrite_trylock(), otherwise, it will cause
> deadlock as below:
>
> - freeze_super
> - sb_wait_write(SB_FREEZE_WRITE)
> - sb_wait_write(SB_FREEZE_PAGEFAULT)
> - sb_wait_write(SB_FREEZE_FS)
> - sync
> - iterate_supers
> - super_lock_shared
> - down_read(&sb->s_umount)
> - sync_fs_one_sb
> - f2fs_sync_fs
> - f2fs_issue_checkpoint
> - wait_for_completion
> -
> issue_checkpoint_thread
> -
> sb_start_intwrite(sbi->sb);
>
> - thaw_super
> - super_lock_excl
> - down_write(&sb->s_umount)
>
> Thanks,
>
> >
> > Fixes: 261eeb9c1585 ("f2fs: introduce checkpoint_merge mount option")
> > Cc: Daeho Jeong <daehoje...@google.com>
> > Signed-off-by: Chao Yu <c...@kernel.org>
> > ---
> > fs/f2fs/checkpoint.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index 55d444bec5c0..66eaad591b60 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -1828,8 +1828,11 @@ static int issue_checkpoint_thread(void *data)
> > if (kthread_should_stop())
> > return 0;
> >
> > - if (!llist_empty(&cprc->issue_list))
> > + if (!llist_empty(&cprc->issue_list)) {
> > + sb_start_intwrite(sbi->sb);
> > __checkpoint_and_complete_reqs(sbi);
> > + sb_end_intwrite(sbi->sb);
> > + }
> >
> > wait_event_interruptible(*q,
> > kthread_should_stop() || !llist_empty(&cprc->issue_list));
>
>
Reviewed-by: Daeho Jeong <daehoje...@google.com>
Thanks.
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