linux-kernel - Re: [PATCH] f2fs: fix to cover allocate

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Message-ID: <YH8cwK+g2PpjBK0Y@google.com>
Date:   Tue, 20 Apr 2021 11:26:08 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH] f2fs: fix to cover allocate_segment() with lock

On 04/20, Chao Yu wrote:
> On 2021/4/20 0:57, Jaegeuk Kim wrote:
> > On 04/14, Chao Yu wrote:
> > > As we did for other cases, in fix_curseg_write_pointer(), let's
> > > change as below:
> > > - use callback function s_ops->allocate_segment() instead of
> > > raw function allocate_segment_by_default();
> > > - cover allocate_segment() with curseg_lock and sentry_lock.
> > > 
> > > Signed-off-by: Chao Yu <yuchao0@...wei.com>
> > > ---
> > >   fs/f2fs/segment.c | 7 ++++++-
> > >   1 file changed, 6 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > > index b2ee6b7791b0..daf9531ec58f 100644
> > > --- a/fs/f2fs/segment.c
> > > +++ b/fs/f2fs/segment.c
> > > @@ -4848,7 +4848,12 @@ static int fix_curseg_write_pointer(struct f2fs_sb_info *sbi, int type)
> > >   	f2fs_notice(sbi, "Assign new section to curseg[%d]: "
> > >   		    "curseg[0x%x,0x%x]", type, cs->segno, cs->next_blkoff);
> > > -	allocate_segment_by_default(sbi, type, true);
> > > +
> > > +	down_read(&SM_I(sbi)->curseg_lock);
> > > +	down_write(&SIT_I(sbi)->sentry_lock);
> > > +	SIT_I(sbi)->s_ops->allocate_segment(sbi, type, true);
> > > +	up_write(&SIT_I(sbi)->sentry_lock);
> > > +	up_read(&SM_I(sbi)->curseg_lock);
> > 
> > Seems f2fs_allocate_new_section()?
> 
> f2fs_allocate_new_section() will allocate new section only when current
> section has been initialized and has valid block/ckpt_block.
> 
> It looks fix_curseg_write_pointer() wants to force migrating current segment
> to new section whenever write pointer and curseg->next_blkoff is inconsistent.
> 
> So how about adding a parameter to force f2fs_allocate_new_section() to
> allocate new section?

I think that can be doable. Hope to avoid native calls as much as possible.

> 
> Thanks,
> 
> > 
> > >   	/* check consistency of the zone curseg pointed to */
> > >   	if (check_zone_write_pointer(sbi, zbd, &zone))
> > > -- 
> > > 2.29.2
> > .
> >