Merge tag 'v3.10.62' into update

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / mm / swap_state.c

diff --git a/mm/swap_state.c b/mm/swap_state.c
index b3d40dcf36247975ac05b1f7a7119521e7cb65bb..c27a26abb78c6d912b1561c284b10470d0a00abf 100644 (file)
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -168,7 +168,11 @@ int add_to_swap(struct page *page, struct list_head *list)
        VM_BUG_ON(!PageLocked(page));
        VM_BUG_ON(!PageUptodate(page));
 
+#ifndef CONFIG_MEMCG
        entry = get_swap_page();
+#else
+       entry = get_swap_page_by_memcg(page);
+#endif
        if (!entry.val)
                return 0;
 
@@ -336,8 +340,24 @@ 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.
                 */
                err = swapcache_prepare(entry);
-               if (err == -EEXIST) {   /* seems racy */
+               if (err == -EEXIST) {
                        radix_tree_preload_end();
+                       /*
+                        * We might race against get_swap_page() and stumble
+                        * across a SWAP_HAS_CACHE swap_map entry whose page
+                        * has not been brought into the swapcache yet, while
+                        * the other end is scheduled away waiting on discard
+                        * I/O completion at scan_swap_map().
+                        *
+                        * In order to avoid turning this transitory state
+                        * into a permanent loop around this -EEXIST case
+                        * if !CONFIG_PREEMPT and the I/O completion happens
+                        * to be waiting on the CPU waitqueue where we are now
+                        * busy looping, we just conditionally invoke the
+                        * scheduler here, if there are some more important
+                        * tasks to run.
+                        */
+                       cond_resched();
                        continue;
                }
                if (err) {              /* swp entry is obsolete ? */