linux-kernel - [PATCH] swap: Delete the "last_in_cluster < scan_base" loop in the body of scan_swap

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Date:	Mon,  2 Jun 2014 19:54:13 +0800
From:	Chen Yucong <slaoub@...il.com>
To:	shli@...nel.org
Cc:	hughd@...gle.com, akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Chen Yucong <slaoub@...il.com>
Subject: [PATCH] swap: Delete  the "last_in_cluster < scan_base" loop in the body of scan_swap_map()

>From commit ebc2a1a69111, we can find that all SWP_SOLIDSTATE "seek is cheap"(SSD case) 
has already gone to si->cluster_info scan_swap_map_try_ssd_cluster() route. So that the
"last_in_cluster < scan_base" loop in the body of scan_swap_map() has already become a 
dead code snippet, and it should have been deleted.

This patch is to delete the redundant loop as Hugh and Shaohua suggested.

Signed-off-by: Chen Yucong <slaoub@...il.com>
---
 mm/swapfile.c |   20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index beeeef8..1b44bd9 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -549,26 +549,6 @@ static unsigned long scan_swap_map(struct swap_info_struct *si,
 			}
 		}
 
-		offset = si->lowest_bit;
-		last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
-
-		/* Locate the first empty (unaligned) cluster */
-		for (; last_in_cluster < scan_base; offset++) {
-			if (si->swap_map[offset])
-				last_in_cluster = offset + SWAPFILE_CLUSTER;
-			else if (offset == last_in_cluster) {
-				spin_lock(&si->lock);
-				offset -= SWAPFILE_CLUSTER - 1;
-				si->cluster_next = offset;
-				si->cluster_nr = SWAPFILE_CLUSTER - 1;
-				goto checks;
-			}
-			if (unlikely(--latency_ration < 0)) {
-				cond_resched();
-				latency_ration = LATENCY_LIMIT;
-			}
-		}
-
 		offset = scan_base;
 		spin_lock(&si->lock);
 		si->cluster_nr = SWAPFILE_CLUSTER - 1;
-- 
1.7.10.4

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