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Date: Fri, 10 Nov 2023 13:23:09 +0000
From: Matthew Wilcox <willy@infradead.org>
To: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Hannes Reinecke <hare@suse.de>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Pankaj Raghav <p.raghav@samsung.com>, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v2 3/7] buffer: Fix grow_buffers() for block size >
 PAGE_SIZE
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On Fri, Nov 10, 2023 at 08:29:41PM +0900, Ryusuke Konishi wrote:
> On Fri, Nov 10, 2023 at 3:37 PM Ryusuke Konishi wrote:
> > > +       return grow_dev_folio(bdev, block, pos / PAGE_SIZE, size, gfp);
> >
> > "pos" has a loff_t type (= long long type).
> > Was it okay to do C division directly on 32-bit architectures?
> 
> Similar to the comment for patch 5/7, can we safely use the generally
> less expensive shift operation "pos >> PAGE_SHIFT" here ?

If your compiler sees x / 4096 and doesn't optimise it to x >> 12,
you need a better compiler.