Re: [PATCH] swap: Delete the "last_in_cluster < scan_base" loop in the body of scan_swap_map()

From: Hugh Dickins
Date: Mon Jun 02 2014 - 19:27:50 EST


On Mon, 2 Jun 2014, Chen Yucong wrote:

> 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@xxxxxxxxx>

That is very nice, thank you.

Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>

But it does beg for just a little more: perhaps Andrew can kindly fold in:
---

mm/swapfile.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)

--- chen/mm/swapfile.c 2014-06-02 15:55:44.812368186 -0700
+++ hugh/mm/swapfile.c 2014-06-02 16:15:20.344396124 -0700
@@ -505,13 +505,10 @@ static unsigned long scan_swap_map(struc
/*
* 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 */
--
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