Re: [PATCH] f2fs: fix iostat parameter for discard

[Chao Yu]

On 2022/12/13 6:59, Jaegeuk Kim wrote:
> 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@xxxxxxxx>
> > > ---
> > >    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.

I guess there is some private scripts in OEM rely on this, and I don't
see any non-Android users using this.

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

What do you think of extending this function to support io_counts?

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

Thanks,

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