thp: allow a hwpoisoned head page to be put back to LRU

Andrea Arcangeli pointed out to me that a check in __memory_failure()
which was intended to prevent THP tail pages from being checked for the
absence of the PG_lru flag (something that is always the case), was also
preventing THP head pages from being checked.

A THP head page could actually benefit from the call to shake_page() by
ending up being put back to a LRU, provided it had been waiting in a
pagevec array.

Andrea suggested that the "!PageTransCompound(p)" in the if-statement
should be replaced by a "!PageTransTail(p)", thus allowing THP head pages
to be checked and possibly shaken.

Signed-off-by: Dean Nelson <dnelson@redhat.com>
Cc: Jin Dongming <jin.dongming@np.css.fujitsu.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index e90a673..6b25758 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -414,11 +414,26 @@ static inline int PageTransHuge(struct page *page)
        return PageHead(page);
 }
 
+/*
+ * PageTransCompound returns true for both transparent huge pages
+ * and hugetlbfs pages, so it should only be called when it's known
+ * that hugetlbfs pages aren't involved.
+ */
 static inline int PageTransCompound(struct page *page)
 {
        return PageCompound(page);
 }
 
+/*
+ * PageTransTail returns true for both transparent huge pages
+ * and hugetlbfs pages, so it should only be called when it's known
+ * that hugetlbfs pages aren't involved.
+ */
+static inline int PageTransTail(struct page *page)
+{
+       return PageTail(page);
+}
+
 #else
 
 static inline int PageTransHuge(struct page *page)
@@ -430,6 +445,11 @@ static inline int PageTransCompound(struct page *page)
 {
        return 0;
 }
+
+static inline int PageTransTail(struct page *page)
+{
+       return 0;
+}
 #endif
 
 #ifdef CONFIG_MMU

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 56080ea..c22076f 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1063,7 +1063,7 @@ int __memory_failure(unsigned long pfn, int trapno, int flags)
         * The check (unnecessarily) ignores LRU pages being isolated and
         * walked by the page reclaim code, however that's not a big loss.
         */
-       if (!PageHuge(p) && !PageTransCompound(p)) {
+       if (!PageHuge(p) && !PageTransTail(p)) {
                if (!PageLRU(p))
                        shake_page(p, 0);
                if (!PageLRU(p)) {