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SubjectRe: [PATCH 1/2] f2fs: Fix mount failure due to SPO after a successful online resize FS
Hi Chao,

On Fri, Feb 28, 2020 at 04:35:37PM +0800, Chao Yu wrote:
> Hi Sahitya,
>
> Good catch.
>
> On 2020/2/27 18:39, Sahitya Tummala wrote:
> > Even though online resize is successfully done, a SPO immediately
> > after resize, still causes below error in the next mount.
> >
> > [ 11.294650] F2FS-fs (sda8): Wrong user_block_count: 2233856
> > [ 11.300272] F2FS-fs (sda8): Failed to get valid F2FS checkpoint
> >
> > This is because after FS metadata is updated in update_fs_metadata()
> > if the SBI_IS_DIRTY is not dirty, then CP will not be done to reflect
> > the new user_block_count.
> >
> > Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> > ---
> > fs/f2fs/gc.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index a92fa49..a14a75f 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -1577,6 +1577,7 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
> >
> > update_fs_metadata(sbi, -secs);
> > clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
>
> Need a barrier here to keep order in between above code and set_sbi_flag(DIRTY)?

I don't think a barrier will help here. Let us say there is a another context
doing CP already, then it races with update_fs_metadata(), so it may or may not
see the resize updates and it will also clear the SBI_IS_DIRTY flag set by resize
(even with a barrier).

I think we need to synchronize this with CP context, so that these resize changes
will be reflected properly. Please see the new diff below and help with the review.

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index a14a75f..5554af8 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1467,6 +1467,7 @@ static void update_fs_metadata(struct f2fs_sb_info *sbi, int secs)
long long user_block_count =
le64_to_cpu(F2FS_CKPT(sbi)->user_block_count);

+ clear_sbi_flag(sbi, SBI_IS_DIRTY);
SM_I(sbi)->segment_count = (int)SM_I(sbi)->segment_count + segs;
MAIN_SEGS(sbi) = (int)MAIN_SEGS(sbi) + segs;
FREE_I(sbi)->free_sections = (int)FREE_I(sbi)->free_sections + secs;
@@ -1575,9 +1576,12 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
goto out;
}

+ mutex_lock(&sbi->cp_mutex);
update_fs_metadata(sbi, -secs);
clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
set_sbi_flag(sbi, SBI_IS_DIRTY);
+ mutex_unlock(&sbi->cp_mutex);
+
err = f2fs_sync_fs(sbi->sb, 1);
if (err) {
update_fs_metadata(sbi, secs);
thanks,

>
> > + set_sbi_flag(sbi, SBI_IS_DIRTY);
> > err = f2fs_sync_fs(sbi->sb, 1);
> > if (err) {
> > update_fs_metadata(sbi, secs);
>
> Do we need to add clear_sbi_flag(, SBI_IS_DIRTY) into update_fs_metadata(), so above
> path can be covered as well?
>
> Thanks,
>
> >

--
--
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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