linux-kernel - Re: [PATCH 1/4] iomap: make sure iomap_adjust_read_range() are aligned with block

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Message-ID: <eyyshgzsxupyen6ms3izkh45ydh3ekxycpk5p4dbets6mpyhch@q4db2ayr4g3r>
Date: Mon, 15 Sep 2025 10:54:00 +0200
From: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
To: Jinliang Zheng <alexjlzheng@...il.com>
Cc: alexjlzheng@...cent.com, brauner@...nel.org, djwong@...nel.org, 
	hch@...radead.org, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-xfs@...r.kernel.org, yi.zhang@...wei.com
Subject: Re: [PATCH 1/4] iomap: make sure iomap_adjust_read_range() are
 aligned with block_size

On Sun, Sep 14, 2025 at 08:40:06PM +0800, Jinliang Zheng wrote:
> On Sun, 14 Sep 2025 13:45:16 +0200, kernel@...kajraghav.com wrote:
> > On Sat, Sep 14, 2025 at 11:37:15AM +0800, alexjlzheng@...il.com wrote:
> > > From: Jinliang Zheng <alexjlzheng@...cent.com>
> > > 
> > > iomap_folio_state marks the uptodate state in units of block_size, so
> > > it is better to check that pos and length are aligned with block_size.
> > > 
> > > Signed-off-by: Jinliang Zheng <alexjlzheng@...cent.com>
> > > ---
> > >  fs/iomap/buffered-io.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> > > index fd827398afd2..0c38333933c6 100644
> > > --- a/fs/iomap/buffered-io.c
> > > +++ b/fs/iomap/buffered-io.c
> > > @@ -234,6 +234,9 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
> > >  	unsigned first = poff >> block_bits;
> > >  	unsigned last = (poff + plen - 1) >> block_bits;
> > >  
> > > +	WARN_ON(*pos & (block_size - 1));
> > > +	WARN_ON(length & (block_size - 1));
> > Any reason you chose WARN_ON instead of WARN_ON_ONCE?
> 
> I just think it's a fatal error that deserves attention every time
> it's triggered.
> 

Is this a general change or does your later changes depend on these on
warning to work correctly?

> > 
> > I don't see WARN_ON being used in iomap/buffered-io.c.
> 
> I'm not sure if there are any community guidelines for using these
> two macros. If there are, please let me know and I'll be happy to
> follow them as a guide.

We typically use WARN_ON_ONCE to prevent spamming.

--
Pankaj