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

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

[Chao Yu]

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 <daehojeong@google.com>
Signed-off-by: Chao Yu <chao@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));
-- 
2.40.1



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[f2fs-dev] [PATCH 2/2] f2fs: fix to use sb_{start, end}_intwrite{_trylock, }() in gc_thread_func()

[Chao Yu]

Since background GC is f2fs inner operation, so, let's use
sb_{start,end}_intwrite{_trylock,}() instead of
sb_{start,end}_write{_trylock,}() in gc_thread_func().

Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/gc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index ef667fec9a12..004587ac5530 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -76,7 +76,7 @@ static int gc_thread_func(void *data)
 			f2fs_stop_checkpoint(sbi, false,
 					STOP_CP_REASON_FAULT_INJECT);
 
-		if (!sb_start_write_trylock(sbi->sb)) {
+		if (!sb_start_intwrite_trylock(sbi->sb)) {
 			stat_other_skip_bggc_count(sbi);
 			continue;
 		}
@@ -163,7 +163,7 @@ static int gc_thread_func(void *data)
 			}
 			spin_unlock(&sbi->gc_remaining_trials_lock);
 		}
-		sb_end_write(sbi->sb);
+		sb_end_intwrite(sbi->sb);
 
 	} while (!kthread_should_stop());
 	return 0;
-- 
2.40.1



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

[Chao Yu]

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 <daehojeong@google.com>
> Signed-off-by: Chao Yu <chao@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));


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

[Daeho Jeong]

On Sat, Jun 8, 2024 at 5:36 AM Chao Yu <chao@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 <daehojeong@google.com>
> > Signed-off-by: Chao Yu <chao@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 <daehojeong@google.com>

Thanks.



> _______________________________________________
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> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel


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Re: [f2fs-dev] [PATCH 2/2] f2fs: fix to use sb_{start, end}_intwrite{_trylock, }() in gc_thread_func()

[Chao Yu]

On 2024/6/6 17:52, Chao Yu wrote:
> Since background GC is f2fs inner operation, so, let's use
> sb_{start,end}_intwrite{_trylock,}() instead of
> sb_{start,end}_write{_trylock,}() in gc_thread_func().

It may cause racing in between gc_thread and freeze_super(), result in
writeback of dirty page after ->freeze, so please ignore this patch.

- sb_wait_write(sb, SB_FREEZE_WRITE)
- sync_filesystem(sb)
				- sb_start_intwrite_trylock
				 - f2fs_gc
				  : dirty pages
- sb_wait_write(sb, SB_FREEZE_FS)

Thanks,

> 
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
>   fs/f2fs/gc.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index ef667fec9a12..004587ac5530 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -76,7 +76,7 @@ static int gc_thread_func(void *data)
>   			f2fs_stop_checkpoint(sbi, false,
>   					STOP_CP_REASON_FAULT_INJECT);
>   
> -		if (!sb_start_write_trylock(sbi->sb)) {
> +		if (!sb_start_intwrite_trylock(sbi->sb)) {
>   			stat_other_skip_bggc_count(sbi);
>   			continue;
>   		}
> @@ -163,7 +163,7 @@ static int gc_thread_func(void *data)
>   			}
>   			spin_unlock(&sbi->gc_remaining_trials_lock);
>   		}
> -		sb_end_write(sbi->sb);
> +		sb_end_intwrite(sbi->sb);
>   
>   	} while (!kthread_should_stop());
>   	return 0;


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

[Chao Yu]

Hi all,

Please ignore this patch, because during freeze_super(), it will call
sync_fs() to clear all dirty data, there should be no race case after
that.

Thanks,

On 2024/6/10 23:10, Daeho Jeong wrote:
> On Sat, Jun 8, 2024 at 5:36 AM Chao Yu <chao@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 <daehojeong@google.com>
>>> Signed-off-by: Chao Yu <chao@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 <daehojeong@google.com>
> 
> Thanks.
> 
> 
> 
>> _______________________________________________
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>> Linux-f2fs-devel@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel


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