mm: Use owner_priv bit for PageSwapCache, valid when PageSwapBacked

A page is not added to the swap cache without being swap backed,
so PageSwapBacked mappings can use PG_owner_priv_1 for PageSwapCache.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 74e4dda912384e3ec15df7c3c15449795cda634e..a57c909a15e419943ee1fc565c6104017fe6fb11 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -87,7 +87,6 @@ enum pageflags {
        PG_private_2,           /* If pagecache, has fs aux data */
        PG_writeback,           /* Page is under writeback */
        PG_head,                /* A head page */
-       PG_swapcache,           /* Swap page: swp_entry_t in private */
        PG_mappedtodisk,        /* Has blocks allocated on-disk */
        PG_reclaim,             /* To be reclaimed asap */
        PG_swapbacked,          /* Page is backed by RAM/swap */
@@ -110,6 +109,9 @@ enum pageflags {
        /* Filesystems */
        PG_checked = PG_owner_priv_1,
 
+       /* SwapBacked */
+       PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */
+
        /* Two page bits are conscripted by FS-Cache to maintain local caching
         * state.  These bits are set on pages belonging to the netfs's inodes
         * when those inodes are being locally cached.
@@ -314,7 +316,13 @@ PAGEFLAG_FALSE(HighMem)
 #endif
 
 #ifdef CONFIG_SWAP
-PAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
+static __always_inline int PageSwapCache(struct page *page)
+{
+       return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);
+
+}
+SETPAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
+CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
 #else
 PAGEFLAG_FALSE(SwapCache)
 #endif
@@ -701,12 +709,12 @@ static inline void ClearPageSlabPfmemalloc(struct page *page)
  * Flags checked when a page is freed.  Pages being freed should not have
  * these flags set.  It they are, there is a problem.
  */
-#define PAGE_FLAGS_CHECK_AT_FREE \
-       (1UL << PG_lru   | 1UL << PG_locked    | \
-        1UL << PG_private | 1UL << PG_private_2 | \
-        1UL << PG_writeback | 1UL << PG_reserved | \
-        1UL << PG_slab  | 1UL << PG_swapcache | 1UL << PG_active | \
-        1UL << PG_unevictable | __PG_MLOCKED)
+#define PAGE_FLAGS_CHECK_AT_FREE                               \
+       (1UL << PG_lru          | 1UL << PG_locked      |       \
+        1UL << PG_private      | 1UL << PG_private_2   |       \
+        1UL << PG_writeback    | 1UL << PG_reserved    |       \
+        1UL << PG_slab         | 1UL << PG_active      |       \
+        1UL << PG_unevictable  | __PG_MLOCKED)
 
 /*
  * Flags checked when a page is prepped for return by the page allocator.

diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index 5a81ab48a2fb2921328e098c388e77d58a765147..30c2adbdebe85b9bcb32a4499fb19ef701f848f6 100644 (file)
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -95,7 +95,6 @@
        {1UL << PG_private_2,           "private_2"     },              \
        {1UL << PG_writeback,           "writeback"     },              \
        {1UL << PG_head,                "head"          },              \
-       {1UL << PG_swapcache,           "swapcache"     },              \
        {1UL << PG_mappedtodisk,        "mappedtodisk"  },              \
        {1UL << PG_reclaim,             "reclaim"       },              \
        {1UL << PG_swapbacked,          "swapbacked"    },              \

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 19e796d36a629147dd36217ecab34934300dc660..f283c7e0a2a302c617c03a3aebf60e262b94a895 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -764,12 +764,11 @@ static int me_huge_page(struct page *p, unsigned long pfn)
  */
 
 #define dirty          (1UL << PG_dirty)
-#define sc             (1UL << PG_swapcache)
+#define sc             ((1UL << PG_swapcache) | (1UL << PG_swapbacked))
 #define unevict                (1UL << PG_unevictable)
 #define mlock          (1UL << PG_mlocked)
 #define writeback      (1UL << PG_writeback)
 #define lru            (1UL << PG_lru)
-#define swapbacked     (1UL << PG_swapbacked)
 #define head           (1UL << PG_head)
 #define slab           (1UL << PG_slab)
 #define reserved       (1UL << PG_reserved)
@@ -819,7 +818,6 @@ static struct page_state {
 #undef mlock
 #undef writeback
 #undef lru
-#undef swapbacked
 #undef head
 #undef slab
 #undef reserved

diff --git a/mm/migrate.c b/mm/migrate.c
index 0ed24b1fa77b89cd49738390cda724c5e74008f8..87f4d0f818194ea68cd323b1bcf84dd430b826a3 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -466,13 +466,15 @@ int migrate_page_move_mapping(struct address_space *mapping,
         */
        newpage->index = page->index;
        newpage->mapping = page->mapping;
-       if (PageSwapBacked(page))
-               __SetPageSwapBacked(newpage);
-
        get_page(newpage);      /* add cache reference */
-       if (PageSwapCache(page)) {
-               SetPageSwapCache(newpage);
-               set_page_private(newpage, page_private(page));
+       if (PageSwapBacked(page)) {
+               __SetPageSwapBacked(newpage);
+               if (PageSwapCache(page)) {
+                       SetPageSwapCache(newpage);
+                       set_page_private(newpage, page_private(page));
+               }
+       } else {
+               VM_BUG_ON_PAGE(PageSwapCache(page), page);
        }
 
        /* Move dirty while page refs frozen and newpage not yet exposed */