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Date: Mon, 25 Nov 2013 17:21:52 +0900
From: Minchan Kim <minchan@kernel.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Dave Chinner <david@fromorbit.com>, Rik van Riel <riel@redhat.com>,
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Subject: Re: [patch 3/9] mm: shmem: save one radix tree lookup when
 truncating swapped pages
Message-ID: <20131125082152.GC4731@bbox>
References: <1385336308-27121-1-git-send-email-hannes@cmpxchg.org>
 <1385336308-27121-4-git-send-email-hannes@cmpxchg.org>
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On Sun, Nov 24, 2013 at 06:38:22PM -0500, Johannes Weiner wrote:
> Page cache radix tree slots are usually stabilized by the page lock,
> but shmem's swap cookies have no such thing.  Because the overall
> truncation loop is lockless, the swap entry is currently confirmed by
> a tree lookup and then deleted by another tree lookup under the same
> tree lock region.
> 
> Use radix_tree_delete_item() instead, which does the verification and
> deletion with only one lookup.  This also allows removing the
> delete-only special case from shmem_radix_tree_replace().
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Minchan Kim <minchan@kernel.org>

Nice cleanup!

-- 
Kind regards,
Minchan Kim