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From:   Daeho Jeong <daeho43@gmail.com>
Date:   Mon, 11 Oct 2021 09:02:47 -0700
Message-ID: <CACOAw_zfDZMB4pLEuHWU5YcKnAtfBBTSuXwXy+L2rNJxXC3ysg@mail.gmail.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: include non-compressed blocks in compr_written_block
To:     Chao Yu <chao@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com,
        Daeho Jeong <daehojeong@google.com>
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> > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > index c1bf9ad4c220..9b663eaf4805 100644
> > --- a/fs/f2fs/compress.c
> > +++ b/fs/f2fs/compress.c
> > @@ -1530,6 +1530,7 @@ int f2fs_write_multi_pages(struct compress_ctx *cc,
> >       if (cluster_may_compress(cc)) {
> >               err = f2fs_compress_pages(cc);
> >               if (err == -EAGAIN) {
> > +                     add_compr_block_stat(cc->inode, cc->cluster_size);
>
> Shouldn't we relocate this after 'write' label?
>
> One more concern, it looks we've changed what compr_block stat indicated,
> literally, the block we account should be compressed..., how about accounting
> it by introducing .presist_blocks, used_blocks or occupied_blocks.... thoughts?
>

What I wanted to add here is just one case in which compression was
tried, but couldn't save any block, so gave up.
If we put this below the "write" label, we will count blocks, even if
the file is turned off for compression in "user-controlled
compression" mode.
Like the commit comment says, I want to estimate the overall compression rate.
But, if we include every other compression disabled condition, it
won't work like that.

Thanks,