linux-kernel - Re: [PATCH 4/5] mm: Use radix_tree_iter

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Date:	Fri, 29 Jan 2016 15:45:59 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>
Cc:	Matthew Wilcox <willy@...ux.intel.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 4/5] mm: Use radix_tree_iter_retry()

On 01/27/2016 10:17 PM, Matthew Wilcox wrote:
> From: Matthew Wilcox <willy@...ux.intel.com>
> 
> Instead of a 'goto restart', we can now use radix_tree_iter_retry()
> to restart from our current position.  This will make a difference
> when there are more ways to happen across an indirect pointer.  And it
> eliminates some confusing gotos.
> 
> Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>

[...]

> diff --git a/mm/shmem.c b/mm/shmem.c
> index fa2ceb2d2655..6ec14b70d82d 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -388,8 +388,10 @@ restart:
>  		 * don't need to reset the counter, nor do we risk infinite
>  		 * restarts.
>  		 */
> -		if (radix_tree_deref_retry(page))
> -			goto restart;
> +		if (radix_tree_deref_retry(page)) {
> +			slot = radix_tree_iter_retry(&iter);
> +			continue;
> +		}
>  
>  		if (radix_tree_exceptional_entry(page))
>  			swapped++;

This should be applied on top. There are no restarts anymore.

----8<----
>From 3b0bdd370b57fb6d83b213e140cd1fb0e8962af8 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@...e.cz>
Date: Fri, 29 Jan 2016 15:41:31 +0100
Subject: [PATCH] mm: Use radix_tree_iter_retry()-fix

Remove now-obsolete-and-misleading comment.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/shmem.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 8f89abd4eaee..4d758938340c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -382,11 +382,6 @@ unsigned long shmem_partial_swap_usage(struct address_space *mapping,
 
 		page = radix_tree_deref_slot(slot);
 
-		/*
-		 * This should only be possible to happen at index 0, so we
-		 * don't need to reset the counter, nor do we risk infinite
-		 * restarts.
-		 */
 		if (radix_tree_deref_retry(page)) {
 			slot = radix_tree_iter_retry(&iter);
 			continue;
-- 
2.7.0