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-rw-r--r--mm/swapfile.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 8a6cdf9e55f9..811d90e1c929 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -37,6 +37,7 @@
#include <linux/swapfile.h>
#include <linux/export.h>
#include <linux/swap_slots.h>
+#include <linux/sort.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
@@ -1198,6 +1199,13 @@ void put_swap_page(struct page *page, swp_entry_t entry)
swapcache_free_cluster(entry);
}
+static int swp_entry_cmp(const void *ent1, const void *ent2)
+{
+ const swp_entry_t *e1 = ent1, *e2 = ent2;
+
+ return (int)swp_type(*e1) - (int)swp_type(*e2);
+}
+
void swapcache_free_entries(swp_entry_t *entries, int n)
{
struct swap_info_struct *p, *prev;
@@ -1208,6 +1216,14 @@ void swapcache_free_entries(swp_entry_t *entries, int n)
prev = NULL;
p = NULL;
+
+ /*
+ * Sort swap entries by swap device, so each lock is only taken once.
+ * nr_swapfiles isn't absolutely correct, but the overhead of sort() is
+ * so low that it isn't necessary to optimize further.
+ */
+ if (nr_swapfiles > 1)
+ sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL);
for (i = 0; i < n; ++i) {
p = swap_info_get_cont(entries[i], prev);
if (p)