2024-06-06 10:31:16

by Chao Yu

Subject: [PATCH 1/2] f2fs: fix to add missing sb_{start,end}_intwrite() for ckpt thread

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.

Fixes: 261eeb9c1585 ("f2fs: introduce checkpoint_merge mount option")
Cc: Daeho Jeong <[email protected]>
Signed-off-by: Chao Yu <[email protected]>
---
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));
--
2.40.1

2024-06-08 12:34:58

by Chao Yu

Subject: Re: [PATCH 1/2] f2fs: fix to add missing sb_{start,end}_intwrite() for ckpt thread

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 <[email protected]>
> Signed-off-by: Chao Yu <[email protected]>
> ---
> 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));

2024-06-10 15:11:16

by Daeho Jeong

Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: fix to add missing sb_{start, end}_intwrite() for ckpt thread

On Sat, Jun 8, 2024 at 5:36 AM Chao Yu <[email protected]> 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 <[email protected]>
> > Signed-off-by: Chao Yu <[email protected]>
> > ---
> > 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 <[email protected]>

Thanks.



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