[PATCH] mm: Add error check after call to rmap_walk in the function page_referenced

[Nicholas Krause <xerofoify@gmail.com>]

This adds a return check after the call to the function rmap_walk
in the function page_referenced as this function call can fail
and thus should signal callers of page_referenced if this happens
by returning the SWAP macro return value as returned by rmap_walk
here. In addition also check if have locked the page pointer as
passed to this particular and unlock it with unlock_page if this
page is locked before returning our SWAP marco return code from
rmap_walk.

Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
---
 mm/rmap.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 171b687..e4df848 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -814,7 +814,9 @@ static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
  * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
  *
  * Quick test_and_clear_referenced for all mappings to a page,
- * returns the number of ptes which referenced the page.
+ * returns the number of ptes which referenced the page.On
+ * error returns either zero or the error code returned from
+ * the failed call to rmap_walk.
  */
 int page_referenced(struct page *page,
 		    int is_locked,
@@ -855,7 +857,13 @@ int page_referenced(struct page *page,
 		rwc.invalid_vma = invalid_page_referenced_vma;
 	}
 
+
 	ret = rmap_walk(page, &rwc);
+	if (!ret) {
+		if (we_locked)
+			unlock_page(page);
+		return ret;
+	}
 	*vm_flags = pra.vm_flags;
 
 	if (we_locked)
-- 
2.1.4

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