linux-kernel - Re: [PATCH] f2fs: fix iostat parameter for discard

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Date:   Mon, 12 Dec 2022 14:59:09 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     Yangtao Li <frank.li@...o.com>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: fix iostat parameter for discard

On 12/11, Chao Yu wrote:
> On 2022/12/5 22:56, Yangtao Li wrote:
> > Just like other data we count uses the number of bytes as the basic unit,
> > but discard uses the number of cmds as the statistical unit. In fact the
> > discard command contains the number of blocks, so let's change to the
> > number of bytes as the base unit.
> > 
> > Fixes: b0af6d491a6b ("f2fs: add app/fs io stat")
> > 
> > Signed-off-by: Yangtao Li <frank.li@...o.com>
> > ---
> >   fs/f2fs/segment.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 9486ca49ecb1..bc262e17b279 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1181,7 +1181,7 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
> >   		atomic_inc(&dcc->issued_discard);
> > -		f2fs_update_iostat(sbi, NULL, FS_DISCARD, 1);
> > +		f2fs_update_iostat(sbi, NULL, FS_DISCARD, len * F2FS_BLKSIZE);
> 
> In order to avoid breaking its usage of application, how about keeping
> FS_DISCARD as it is, and add FS_DISCARD_IO to account discard bytes?

I picked this to match the f2fs_update_iostat() definition. Do we know
how many applications will be affected? I don't have any at a glance in
Android tho.

void f2fs_update_iostat(struct f2fs_sb_info *sbi, struct inode *inode,
                        enum iostat_type type, unsigned long long io_bytes)


> 
> Thanks,
> 
> >   		lstart += len;
> >   		start += len;