linux-kernel - Re: [PATCH 2/4] filemap: kill page_cache_read usage in filemap

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Message-ID: <20181205215209.GA13938@cmpxchg.org>
Date:   Wed, 5 Dec 2018 13:52:09 -0800
From:   Johannes Weiner <hannes@...xchg.org>
To:     Josef Bacik <josef@...icpanda.com>
Cc:     kernel-team@...com, linux-kernel@...r.kernel.org, tj@...nel.org,
        david@...morbit.com, akpm@...ux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, riel@...hat.com,
        jack@...e.cz
Subject: Re: [PATCH 2/4] filemap: kill page_cache_read usage in filemap_fault

On Fri, Nov 30, 2018 at 02:58:10PM -0500, Josef Bacik wrote:
> If we do not have a page at filemap_fault time we'll do this weird
> forced page_cache_read thing to populate the page, and then drop it
> again and loop around and find it.  This makes for 2 ways we can read a
> page in filemap_fault, and it's not really needed.  Instead add a
> FGP_FOR_MMAP flag so that pagecache_get_page() will return a unlocked
> page that's in pagecache.  Then use the normal page locking and readpage
> logic already in filemap_fault.  This simplifies the no page in page
> cache case significantly.
> 
> Signed-off-by: Josef Bacik <josef@...icpanda.com>

That's a great simplification. Looks correct to me.

Acked-by: Johannes Weiner <hannes@...xchg.org>