Re: [f2fs-dev] [PATCH] f2fs: avoid setting SBI_NEED_FSCK on transient resize failure with -EAGAIN

[Daeho Jeong]

On Tue, Aug 18, 2026 at 7:34 PM Chao Yu <chao@xxxxxxxxxx> wrote:
>
> On 8/19/26 01:05, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@xxxxxxxxxx>
> >
> > When f2fs_resize_fs() fails due to transient lock contention or retryable
> > GC failure in free_segment_range() returning -EAGAIN, no filesystem
> > metadata has been modified on-disk yet. The filesystem remains completely
> > consistent and clean.
>
> Any way to make sure EAGAIN is from free_segment_range(), in case we return
> EAGAIN from 1) any other places that we may miss to check now or 2) we changed
> the code to return EAGAIN in future.

Makes sense.

In fact, if free_segment_range() fails with ANY error (e.g., -EAGAIN,
-ENOMEM, -ERESTARTSYS, etc.), no on-disk superblock or filesystem metadata
has been modified yet, and free_segment_range() safely restores all in-memory
counters (MAIN_SECS, free_sections) before returning. Therefore, setting
SBI_NEED_FSCK is not needed for all errors occurring in free_segment_range().

To make this explicit and defensive against any future changes, we can
separate the error recovery path with dedicated labels as follows:

  err = free_segment_range(sbi, secs, false);
  if (err)
- goto recover_out;
+ goto recover_user_blocks;

  update_sb_metadata(sbi, -secs);

...

 recover_out:
+ set_sbi_flag(sbi, SBI_NEED_FSCK);
+ f2fs_err(sbi, "resize_fs failed, should run fsck to repair!");
+recover_user_blocks:
  clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
  if (err) {
- set_sbi_flag(sbi, SBI_NEED_FSCK);
- f2fs_err(sbi, "resize_fs failed, should run fsck to repair!");
-
  spin_lock(&sbi->stat_lock);
  sbi->user_block_count += shrunk_blocks;
  spin_unlock(&sbi->stat_lock);

Thanks,

>
> Thanks,
>
> >
> > However, the current error recovery path unconditionally sets the
> > SBI_NEED_FSCK flag on any error, forcing an unnecessary and time-consuming
> > fsck.f2fs repair on the subsequent mount/reboot.
> >
> > Fix this by guarding set_sbi_flag(sbi, SBI_NEED_FSCK) with
> > `if (err != -EAGAIN)`, avoiding false-positive filesystem corruption
> > flags on transient resize retries.
> >
> > Signed-off-by: Daeho Jeong <daehojeong@xxxxxxxxxx>
> > Signed-off-by: Sunmin Jeong <s_min.jeong@xxxxxxxxxxx>
> > ---
> >  fs/f2fs/gc.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index 192b16ac02f8..787133ee2eb2 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -2446,8 +2446,10 @@ int f2fs_resize_fs(struct file *filp, __u64 block_count)
> >  recover_out:
> >       clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
> >       if (err) {
> > -             set_sbi_flag(sbi, SBI_NEED_FSCK);
> > -             f2fs_err(sbi, "resize_fs failed, should run fsck to repair!");
> > +             if (err != -EAGAIN) {
> > +                     set_sbi_flag(sbi, SBI_NEED_FSCK);
> > +                     f2fs_err(sbi, "resize_fs failed, should run fsck to repair!");
> > +             }
> >
> >               spin_lock(&sbi->stat_lock);
> >               sbi->user_block_count += shrunk_blocks;
>