mm/swapfile.c: delete the "last_in_cluster < scan_base" loop in the body of scan_swap_map()
Via commit ebc2a1a69111 ("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: Chen Yucong <slaoub@gmail.com>
Cc: Shaohua Li <shli@kernel.org>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index beeeef8..4c524f7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -523,13 +523,10 @@
/*
* 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;
+ scan_base = offset = si->lowest_bit;
last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
/* Locate the first empty (unaligned) cluster */
@@ -549,26 +546,6 @@
}
}
- 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;