linux-kernel - Re: [PATCH 2/2] vmscan: use atomic-long for shrinker batching

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Date:	Mon, 22 Aug 2011 14:39:54 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH 2/2] vmscan: use atomic-long for shrinker batching

On Mon, 22 Aug 2011 14:17:27 +0300
Konstantin Khlebnikov <khlebnikov@...nvz.org> wrote:

> Use atomic-long operations instead of looping around cmpxchg().
> 

Seems nice.

> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index 790651b..ac6b8ee 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -34,7 +34,7 @@ struct shrinker {
>  
>  	/* These are for internal use */
>  	struct list_head list;
> -	long nr;	/* objs pending delete */
> +	atomic_long_t nr_in_batch; /* objs pending delete */
>  };

This makes shrinker.h have a dependency on atomic.h.  shrinker.h is a
strange thing that doesn't include its own dependent header files - the
shrinker.h includer is responsible for that.  And they both need
fixups, for safety's sake:

 include/linux/fs.h |    2 +-
 include/linux/mm.h |    1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

--- a/include/linux/mm.h~vmscan-use-atomic-long-for-shrinker-batching-fix
+++ a/include/linux/mm.h
@@ -10,6 +10,7 @@
 #include <linux/mmzone.h>
 #include <linux/rbtree.h>
 #include <linux/prio_tree.h>
+#include <linux/atomic.h>
 #include <linux/debug_locks.h>
 #include <linux/mm_types.h>
 #include <linux/range.h>
--- a/include/linux/fs.h~vmscan-use-atomic-long-for-shrinker-batching-fix
+++ a/include/linux/fs.h
@@ -394,8 +394,8 @@ struct inodes_stat_t {
 #include <linux/semaphore.h>
 #include <linux/fiemap.h>
 #include <linux/rculist_bl.h>
-#include <linux/shrinker.h>
 #include <linux/atomic.h>
+#include <linux/shrinker.h>
 
 #include <asm/byteorder.h>
 
_

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