linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: skip adding a discard command if exists

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Date:   Fri, 17 Nov 2023 09:41:37 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: skip adding a discard command if exists

On 11/15, Chao Yu wrote:
> On 2023/11/15 10:45, Jaegeuk Kim wrote:
> > On 11/15, Chao Yu wrote:
> > > On 2023/11/15 5:24, Jaegeuk Kim wrote:
> > > > When recovering zoned UFS, sometimes we add the same zone to discard multiple
> > > > times. Simple workaround is to bypass adding it.
> > > 
> > > What about skipping f2fs_bug_on() just for zoned UFS case? so that the check
> > > condition can still be used for non-zoned UFS case.
> > 
> > Hmm, I've never seen this bug_on before, but even this really happens, it does
> 
> I've never seen it was been triggered as well.
> 
> > not make sense to move forward to create duplicate commands resulting in a loop.
> 
> Agreed.
> 
> It looks those codes were copied from extent_cache code base, do we need to fix
> all cases to avoid loop?

Not sure other cases yet.. let's do one by one, since I hit this in real.

> 
> > 
> > So, the question is, do we really need to check this? Have we hit this before?
> Not sure, just be worry about that flaw of newly developed feature can make
> code run into that branch.
> 
> Thanks,
> 
> > 
> > > 
> > > Thanks,
> > > 
> > > > 
> > > > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > > > ---
> > > >    fs/f2fs/segment.c | 3 ++-
> > > >    1 file changed, 2 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > > > index 727d016318f9..f4ffd64b44b2 100644
> > > > --- a/fs/f2fs/segment.c
> > > > +++ b/fs/f2fs/segment.c
> > > > @@ -1380,7 +1380,8 @@ static void __insert_discard_cmd(struct f2fs_sb_info *sbi,
> > > >    			p = &(*p)->rb_right;
> > > >    			leftmost = false;
> > > >    		} else {
> > > > -			f2fs_bug_on(sbi, 1);
> > > > +			/* Let's skip to add, if exists */
> > > > +			return;
> > > >    		}
> > > >    	}