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mm: use swp_offset as key in shmem_replace_page()

PATCH New [email protected] 1 participant 1 message Dec 1, 2018

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PATCH 5/31 mm: use swp_offset as key in shmem_replace_page()

From: Yu Zhao <[email protected]>
Subject: mm: use swp_offset as key in shmem_replace_page()

We changed the key of swap cache tree from swp_entry_t.val to swp_offset. We need to do so in shmem_replace_page() as well.

Hugh said:

: shmem_replace_page() has been wrong since the day I wrote it: good : enough to work on swap "type" 0, which is all most people ever use : (especially those few who need shmem_replace_page() at all), but broken : once there are any non-0 swp_type bits set in the higher order bits.

Link http://lkml.kernel.org/r/[email protected] open here
Fixes f6ab1f7f6b2d ("mm, swap: use offset of swap entry as key of swap cache")
Signed-off-by Yu Zhao <[email protected]>
Reviewed-by Matthew Wilcox <[email protected]>
Acked-by Hugh Dickins <[email protected]>
Cc <[email protected]> [4.9+]
Signed-off-by Andrew Morton <[email protected]>

---

 mm/shmem.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
mm/shmem.c renamed from mm/shmem.c~mm-use-swp_offset-as-key-in-shmem_replace_page +4 -2
@@ -1509,11 +1509,13 @@ static int shmem_replace_page(struct pag
 {
 	struct page *oldpage, *newpage;
 	struct address_space *swap_mapping;
+	swp_entry_t entry;
 	pgoff_t swap_index;
 	int error;
 
 	oldpage = *pagep;
-	swap_index = page_private(oldpage);
+	entry.val = page_private(oldpage);
+	swap_index = swp_offset(entry);
 	swap_mapping = page_mapping(oldpage);
 
 	/*

@@ -1532,7 +1534,7 @@ static int shmem_replace_page(struct pag
 	__SetPageLocked(newpage);
 	__SetPageSwapBacked(newpage);
 	SetPageUptodate(newpage);
-	set_page_private(newpage, swap_index);
+	set_page_private(newpage, entry.val);
 	SetPageSwapCache(newpage);
 
 	/*

_