linux-kernel - Re: [f2fs-dev] [PATCH 1/2] f2fs: remove folio_detach_private() in .invalidate_folio and .release

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Date:   Wed, 12 Apr 2023 09:16:28 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: remove folio_detach_private() in
 .invalidate_folio and .release_folio

On 04/11, Jaegeuk Kim wrote:
> On 04/11, Chao Yu wrote:
> > On 2023/4/11 2:33, Jaegeuk Kim wrote:
> > > On 04/10, Chao Yu wrote:
> > > > We have maintain PagePrivate and page_private and page reference
> > > > w/ {set,clear}_page_private_*, it doesn't need to call
> > > > folio_detach_private() in the end of .invalidate_folio and
> > > > .release_folio, remove it and use f2fs_bug_on instead.
> > > > 
> > > > Signed-off-by: Chao Yu <chao@...nel.org>
> > > > ---
> > > >   fs/f2fs/data.c | 7 +++++--
> > > >   1 file changed, 5 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > > > index 4946df6dd253..8b179b4bdc03 100644
> > > > --- a/fs/f2fs/data.c
> > > > +++ b/fs/f2fs/data.c
> > > > @@ -3737,7 +3737,8 @@ void f2fs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
> > > >   			inode->i_ino == F2FS_COMPRESS_INO(sbi))
> > > >   		clear_page_private_data(&folio->page);
> > > > -	folio_detach_private(folio);
> > > > +	f2fs_bug_on(sbi, PagePrivate(&folio->page));
> > > > +	f2fs_bug_on(sbi, page_private(&folio->page));
> > > 
> > > I think we can just check page_private() only.
> > 
> > Why? how about the case PagePrivate was set, but page_private was't? It must
> > be a bug as well?
> 
> Given the code, I think both are set all the time. My concern is someone is
> not doing set/get properly. Actually, I got a panic on page_private() when
> running fsstress overnight. I'm trying to reproduce it to find which bit was
> set.

It turned out that inline bit is somehow set, guessing the bit was not cleared
when the first dirty page was truncated or somewhere else.

Anyway, tooking a look at the usecase of flushing inline_data to inode page
aggressively, I feel it's kinda hack and may increase the checkpoint latency.
Hence, I'd like to remove it simply.

https://lore.kernel.org/linux-f2fs-devel/20230412160810.1534632-1-jaegeuk@kernel.org/T/#t

> 
> > 
> > Thanks,
> > 
> > > 
> > > >   }
> > > >   bool f2fs_release_folio(struct folio *folio, gfp_t wait)
> > > > @@ -3759,7 +3760,9 @@ bool f2fs_release_folio(struct folio *folio, gfp_t wait)
> > > >   	clear_page_private_reference(&folio->page);
> > > >   	clear_page_private_gcing(&folio->page);
> > > > -	folio_detach_private(folio);
> > > > +	f2fs_bug_on(sbi, PagePrivate(&folio->page));
> > > > +	f2fs_bug_on(sbi, page_private(&folio->page));
> > > > +
> > > >   	return true;
> > > >   }
> > > > -- 
> > > > 2.25.1
> 
> 
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