linux-ext4 - Re: [PATCH 1/5] mbcache: correctly handle 'e

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Date:   Sat, 3 Dec 2016 15:28:38 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Eric Biggers <ebiggers@...gle.com>
Cc:     linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>,
        Andreas Gruenbacher <agruenba@...hat.com>
Subject: Re: [PATCH 1/5] mbcache: correctly handle 'e_referenced' bit

On Sat, Nov 26, 2016 at 10:17:57PM -0800, Eric Biggers wrote:
> mbcache entries have an 'e_referenced' bit which users can set with
> mb_cache_entry_touch() to indicate that an entry should be given another
> pass through the LRU list before the shrinker can delete it.  However,
> mb_cache_shrink() actually would, when seeing an e_referenced entry at
> the front of the list (the least-recently used end), place it right at
> the front of the list again.  The next iteration would then remove the
> entry from the list and delete it.  Consequently, e_referenced had
> essentially no effect, so ext2/ext4 xattr blocks would sometimes not be
> reused as often as expected.
> 
> Fix this by making the shrinker move e_referenced entries to the back of
> the list rather than the front.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Thanks, applied.

					- Ted
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