linux-kernel - Re: [PATCH 11/11] afs: Fix dirty-region encoding on ppc32 with 64K pages

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Message-ID: <548209.1603904708@warthog.procyon.org.uk>
Date:   Wed, 28 Oct 2020 17:05:08 +0000
From:   David Howells <dhowells@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     dhowells@...hat.com, linux-afs@...ts.infradead.org,
        kernel test robot <lkp@...el.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/11] afs: Fix dirty-region encoding on ppc32 with 64K pages

Matthew Wilcox <willy@...radead.org> wrote:

> > +{
> > +	if (PAGE_SIZE - 1 <= __AFS_PAGE_PRIV_MASK)
> > +		return 1;
> > +	else
> > +		return PAGE_SIZE / (__AFS_PAGE_PRIV_MASK + 1);
> 
> Could this be DIV_ROUND_UP(PAGE_SIZE, __AFS_PAGE_PRIV_MASK + 1); avoiding
> a conditional?  I appreciate it's calculated at compile time today, but
> it'll be dynamic with THP.

Hmmm - actually, I want a shift size, not a number of bytes as I divide by it
twice in afs_page_dirty().

David