linux-kernel - Re: [PATCH 3/5] iomap: simplify iomap_init() with PAGE

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Date:   Fri, 21 Apr 2023 15:30:17 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Matthew Wilcox <willy@...radead.org>, agk@...hat.com,
        snitzer@...nel.org, philipp.reisner@...bit.com,
        lars.ellenberg@...bit.com, christoph.boehmwalder@...bit.com,
        hch@...radead.org, djwong@...nel.org, minchan@...nel.org,
        senozhatsky@...omium.org, patches@...ts.linux.dev,
        linux-block@...r.kernel.org, linux-mm@...ck.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        dm-devel@...hat.com, drbd-dev@...ts.linbit.com,
        linux-kernel@...r.kernel.org, hare@...e.de, p.raghav@...sung.com,
        da.gomez@...sung.com, kbusch@...nel.org
Subject: Re: [PATCH 3/5] iomap: simplify iomap_init() with PAGE_SECTORS

On Fri, Apr 21, 2023 at 04:24:57PM -0600, Jens Axboe wrote:
> On 4/21/23 4:02 PM, Luis Chamberlain wrote:
> > On Fri, Apr 21, 2023 at 09:14:00PM +0100, Matthew Wilcox wrote:
> >> On Fri, Apr 21, 2023 at 12:58:05PM -0700, Luis Chamberlain wrote:
> >>> Just use the PAGE_SECTORS generic define. This produces no functional
> >>> changes. While at it use left shift to simplify this even further.
> >>
> >> How is FOO << 2 simpler than FOO * 4?
> >>
> >>> -	return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
> >>> +	return bioset_init(&iomap_ioend_bioset, PAGE_SECTORS << 2,
> > 
> > We could just do:
> > 
> > 
> > -	return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
> > +	return bioset_init(&iomap_ioend_bioset, 4 * PAGE_SECTORS,
> > 
> > The shift just seemed optimal if we're just going to change it.
> 
> It's going to generate the same code, but the multiplication is arguably
> easier to read (or harder to misread).

Then let's stick with the 4 * PAGE_SECTORS. Let me know if you need another
patch.

  Luis