linux-kernel - Re: [PATCH] f2fs: compress: remove unneed check condition

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Date:   Sat, 24 Apr 2021 17:47:36 -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: compress: remove unneed check condition

On 04/22, Chao Yu wrote:
> On 2021/4/22 12:04, Jaegeuk Kim wrote:
> > On 04/21, Chao Yu wrote:
> > > In only call path of __cluster_may_compress(), __f2fs_write_data_pages()
> > > has checked SBI_POR_DOING condition, and also cluster_may_compress()
> > > has checked CP_ERROR_FLAG condition, so remove redundant check condition
> > > in __cluster_may_compress() for cleanup.
> > 
> > I think cp_error can get any time without synchronization. Is it safe to say
> > it's redundant?
> 
> Yes,
> 
> But no matter how late we check cp_error, cp_error can happen after our
> check points, it won't cause regression if we remove cp_error check there,
> because for compress write, it uses OPU, it won't overwrite any existed data
> in device.
> 
> Seems it will be more appropriate to check cp_error in
> f2fs_write_compressed_pages() like we did in f2fs_write_single_data_page()
> rather than in __cluster_may_compress().
> 
> BTW, shouldn't we rename __cluster_may_compress() to
> cluster_beyond_filesize() for better readability?

f2fs_cluster_has_data()?

> 
> Thanks,
> 
> > 
> > > 
> > > Signed-off-by: Chao Yu <yuchao0@...wei.com>
> > > ---
> > >   fs/f2fs/compress.c | 5 -----
> > >   1 file changed, 5 deletions(-)
> > > 
> > > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > > index 3c9d797dbdd6..532c311e3a89 100644
> > > --- a/fs/f2fs/compress.c
> > > +++ b/fs/f2fs/compress.c
> > > @@ -906,11 +906,6 @@ static bool __cluster_may_compress(struct compress_ctx *cc)
> > >   		f2fs_bug_on(sbi, !page);
> > > -		if (unlikely(f2fs_cp_error(sbi)))
> > > -			return false;
> > > -		if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
> > > -			return false;
> > > -
> > >   		/* beyond EOF */
> > >   		if (page->index >= nr_pages)
> > >   			return false;
> > > -- 
> > > 2.29.2
> > .
> >