tmpfs: shuffle add_to_swap_caches

add_to_swap_cache doesn't amount to much: merge it into its sole caller
read_swap_cache_async.  But we'll be needing to call __add_to_swap_cache from
shmem.c, so promote it to the new add_to_swap_cache.  Both were static, so
there's no interface confusion to worry about.

And lose that inappropriate "Anon pages are already on the LRU" comment in the
merging: they're not already on the LRU, as Nick Piggin noticed.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
No-problems-with: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 34 deletions

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 18fce3613e5a..c75eda2c9cc5 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -64,10 +64,10 @@ void show_swap_cache_info(void)
 }
 
 /*
- * __add_to_swap_cache resembles add_to_page_cache on swapper_space,
+ * add_to_swap_cache resembles add_to_page_cache on swapper_space,
  * but sets SwapCache flag and private instead of mapping and index.
  */
-static int __add_to_swap_cache(struct page *page, swp_entry_t entry,
+static int add_to_swap_cache(struct page *page, swp_entry_t entry,
                                gfp_t gfp_mask)
 {
         int error;
@@ -94,28 +94,6 @@ static int __add_to_swap_cache(struct page *page, swp_entry_t entry,
         return error;
 }
 
-static int add_to_swap_cache(struct page *page, swp_entry_t entry,
-                                gfp_t gfp_mask)
-{
-        int error;
-
-        BUG_ON(PageLocked(page));
-        if (!swap_duplicate(entry))
-                return -ENOENT;
-
-        SetPageLocked(page);
-        error = __add_to_swap_cache(page, entry, gfp_mask & GFP_KERNEL);
-        /*
-         * Anon pages are already on the LRU, we don't run lru_cache_add here.
-         */
-        if (error) {
-                ClearPageLocked(page);
-                swap_free(entry);
-                return error;
-        }
-        return 0;
-}
-
 /*
  * This must be called only on pages that have
  * been verified to be in the swap cache.
@@ -165,7 +143,7 @@ int add_to_swap(struct page * page, gfp_t gfp_mask)
                 /*
                  * Add it to the swap cache and mark it dirty
                  */
-                err = __add_to_swap_cache(page, entry,
+                err = add_to_swap_cache(page, entry,
                                 gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN);
 
                 switch (err) {
@@ -210,7 +188,7 @@ void delete_from_swap_cache(struct page *page)
  */
 int move_to_swap_cache(struct page *page, swp_entry_t entry)
 {
-        int err = __add_to_swap_cache(page, entry, GFP_ATOMIC);
+        int err = add_to_swap_cache(page, entry, GFP_ATOMIC);
         if (!err) {
                 remove_from_page_cache(page);
                 page_cache_release(page);       /* pagecache ref */
@@ -335,16 +313,21 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
                 }
 
                 /*
+                 * Swap entry may have been freed since our caller observed it.
+                 */
+                if (!swap_duplicate(entry))
+                        break;
+
+                /*
                  * Associate the page with swap entry in the swap cache.
-                 * May fail (-ENOENT) if swap entry has been freed since
-                 * our caller observed it.  May fail (-EEXIST) if there
-                 * is already a page associated with this entry in the
-                 * swap cache: added by a racing read_swap_cache_async,
-                 * or by try_to_swap_out (or shmem_writepage) re-using
-                 * the just freed swap entry for an existing page.
+                 * May fail (-EEXIST) if there is already a page associated
+                 * with this entry in the swap cache: added by a racing
+                 * read_swap_cache_async, or add_to_swap or shmem_writepage
+                 * re-using the just freed swap entry for an existing page.
                  * May fail (-ENOMEM) if radix-tree node allocation failed.
                  */
-                err = add_to_swap_cache(new_page, entry, gfp_mask);
+                SetPageLocked(new_page);
+                err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
                 if (!err) {
                         /*
                          * Initiate read into locked page and return.
@@ -353,7 +336,9 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
                         swap_readpage(NULL, new_page);
                         return new_page;
                 }
-        } while (err != -ENOENT && err != -ENOMEM);
+                ClearPageLocked(new_page);
+                swap_free(entry);
+        } while (err != -ENOMEM);
 
         if (new_page)
                 page_cache_release(new_page);