linux-kernel - Re: [PATCH v4 13/16] mm: Pass pvec directly to find_get

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Message-ID: <20201114152252.GM17076@casper.infradead.org>
Date:   Sat, 14 Nov 2020 15:22:52 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, hughd@...gle.com, hannes@...xchg.org,
        yang.shi@...ux.alibaba.com, dchinner@...hat.com,
        linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>,
        William Kucharski <william.kucharski@...cle.com>
Subject: Re: [PATCH v4 13/16] mm: Pass pvec directly to find_get_entries

On Sat, Nov 14, 2020 at 11:21:33AM +0100, Christoph Hellwig wrote:
> On Thu, Nov 12, 2020 at 09:26:38PM +0000, Matthew Wilcox (Oracle) wrote:
> > +	pvec->nr = ret;
> >  	return ret;
> 
> Do we need to return the number of found entries in addition to storing
> it in the pagevec?

We really only need a bool -- is pvec->nr zero or not.  But we have the
number calculated so we may as well return it.  All the current find_*()
behave this way and I haven't seen enough reason to change it yet.
Making it return void just makes the callers uglier.  I have a batch of
patches to do something similar for find_get_pages / find_get_pages_range
/ pagevec_lookup / pagevec_lookup_range, but I don't need them for the
THP patchset, so I haven't sent them yet.