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-rw-r--r--mm/swapfile.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index e74112e..6c0585b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -22,6 +22,7 @@
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/module.h>
+#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/security.h>
#include <linux/backing-dev.h>
@@ -650,6 +651,8 @@ int reuse_swap_page(struct page *page)
int count;
VM_BUG_ON(!PageLocked(page));
+ if (unlikely(PageKsm(page)))
+ return 0;
count = page_mapcount(page);
if (count <= 1 && PageSwapCache(page)) {
count += page_swapcount(page);
@@ -658,7 +661,7 @@ int reuse_swap_page(struct page *page)
SetPageDirty(page);
}
}
- return count == 1;
+ return count <= 1;
}
/*
@@ -1185,6 +1188,12 @@ static int try_to_unuse(unsigned int type)
* read from disk into another page. Splitting into two
* pages would be incorrect if swap supported "shared
* private" pages, but they are handled by tmpfs files.
+ *
+ * Given how unuse_vma() targets one particular offset
+ * in an anon_vma, once the anon_vma has been determined,
+ * this splitting happens to be just what is needed to
+ * handle where KSM pages have been swapped out: re-reading
+ * is unnecessarily slow, but we can fix that later on.
*/
if (swap_count(*swap_map) &&
PageDirty(page) && PageSwapCache(page)) {