mm, hwpoison: remove recalculating hpage

hpage is never used after try_to_split_thp_page() in memory_failure(), so
we don't have to update hpage.  So let's not recalculate/use hpage.

Suggested-by: "Aneesh Kumar K.V" <[email protected]>
Signed-off-by: Naoya Horiguchi <[email protected]>
Signed-off-by: Oscar Salvador <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Mike Kravetz <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Cc: Aristeu Rozanski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Dmitry Yakunin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Qian Cai <[email protected]>
Cc: Tony Luck <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

mm/memory-failure.c

@@ -1341,7 +1341,6 @@ int memory_failure(unsigned long pfn, int flags)
 		}
 		unlock_page(p);
 		VM_BUG_ON_PAGE(!page_count(p), p);
-		hpage = compound_head(p);
 	}
 
 	/*
@@ -1413,11 +1412,8 @@ int memory_failure(unsigned long pfn, int flags)
 	/*
 	 * Now take care of user space mappings.
 	 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
-	 *
-	 * When the raw error page is thp tail page, hpage points to the raw
-	 * page after thp split.
 	 */
-	if (!hwpoison_user_mappings(p, pfn, flags, &hpage)) {
+	if (!hwpoison_user_mappings(p, pfn, flags, &p)) {
 		action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
 		res = -EBUSY;
 		goto out;