Re: [PATCH v2] f2fs: don't call f2fs_issue_discard_timeout() when discard_cmd_cnt is 0 in f2fs_put_super()

[Chao Yu]

On 2022/12/13 6:45, Jaegeuk Kim wrote:
> On 12/12, Chao Yu wrote:
> > On 2022/12/12 22:14, Yangtao Li wrote:
> > > Hi Chao,
> > >
> > > > The difference here is, if we use f2fs_realtime_discard_enable() in
> > > > f2fs_put_super(), we will only write checkpoint w/ CP_TRIMMED flag
> > > > when discard option is enable and device supports discard.
> > >
> > > > But actually, if discard option is disabled, we still needs to give
> > > > put_super() a chance to write checkpoint w/ CP_TRIMMED flag.
> > >
> > > Why do we still have to set the CP_TRIMMED flag when the discard opt is not set.
> > > Did I miss something?
> >
> > Hi Yangtao,
> >
> > I guess it's up to scenario. e.g.
> >
> > mount w/ nodiscard and use FITRIM to trigger in-batch discard,
> > if we set CP_TRIMMED flag during umount, next time, after mount
> > w/ discard, it doesn't to issue redundant discard.
>
> If fitrim was called with a range, we can get a wrong FI_TRIMMED flag. Isn't it

We can set CP_TRIMMED flag only if fitrim was called on full range w/ 4k granularity,
due to it will check sbi->discard_blks variable to make sure there is no range we
haven't trimmed.

> better to get a full discard range after remount even though some are redundant?

If nodiscard is set, and sbi->discard_blks becomes zero, it says a full range fitrim
was been triggered.

So, previous check condition has no problem, right?

	if ((f2fs_hw_support_discard(sbi) || f2fs_hw_should_discard(sbi)) &&
					!sbi->discard_blks && !dropped) {

Thanks,

> > Thanks,
> >
> > > Thx,
> > > Yangtao