linux-kernel - Re: [PATCH 2/8] mm: Use find_get_swap

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Date:   Thu, 27 Aug 2020 10:22:29 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        William Kucharski <william.kucharski@...cle.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Matthew Auld <matthew.auld@...el.com>,
        Huang Ying <ying.huang@...el.com>,
        intel-gfx@...ts.freedesktop.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/8] mm: Use find_get_swap_page in memcontrol

On Thu, Aug 27, 2020 at 01:59:41PM +0100, Matthew Wilcox wrote:
> On Wed, Aug 26, 2020 at 10:20:02AM -0400, Johannes Weiner wrote:
> > The refactor makes sense to me, but the name is confusing. We're not
> > looking for a swap page, we're primarily looking for a file page in
> > the page cache mapping that's handed in. Only in the special case
> > where it's a shmem mapping and there is a swap entry do we consult the
> > auxiliary swap cache.
> > 
> > How about find_get_page_or_swapcache()? find_get_page_shmemswap()?
> > Maybe you have a better idea. It's a fairly specialized operation that
> > isn't widely used, so a longer name isn't a bad thing IMO.
> 
> Got it.  find_get_incore_page().  I was going to go with inmem, but that
> it matches mincore sold me on it.
>
> /**
>  * find_get_incore_page - Find and get a page from the page or swap caches.
>  * @mapping: The address_space to search.
>  * @index: The page cache index.
>  *
>  * This differs from find_get_page() in that it will also look for the
>  * page in the swap cache.
>  *
>  * Return: The found page or %NULL.
>  */

Nice work, that's perfect.

> I was focusing too much on what the function did, not why it was doing it.

Me too.