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Commit 50088c44 authored by Chen Yucong's avatar Chen Yucong Committed by Linus Torvalds
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mm/swapfile.c: delete the "last_in_cluster < scan_base" loop in the body of scan_swap_map() 



Via commit ebc2a1a6 ("swap: make cluster allocation per-cpu"), 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.

[hughd@google.com: fix comment, simplify code]
Signed-off-by: default avatarChen Yucong <slaoub@gmail.com>
Cc: Shaohua Li <shli@kernel.org>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 100873d7

mm/swapfile.c

+3 −26
Original line number Diff line number Diff line
@@ -523,12 +523,9 @@ static unsigned long scan_swap_map(struct swap_info_struct *si, 
		/*

		 * If seek is expensive, start searching for new cluster from

		 * start of partition, to minimize the span of allocated swap.

		 * But if seek is cheap, search from our current position, so

		 * that swap is allocated from all over the partition: if the

		 * Flash Translation Layer only remaps within limited zones,

		 * we don't want to wear out the first zone too quickly.

		 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info

		 * case, just handled by scan_swap_map_try_ssd_cluster() above.

		 */

		if (!(si->flags & SWP_SOLIDSTATE))

		scan_base = offset = si->lowest_bit;

		last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
@@ -549,26 +546,6 @@ 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;