mm, THP, swap: move anonymous THP split logic to vmscan

The add_to_swap aims to allocate swap_space(ie, swap slot and swapcache)
so if it fails due to lack of space in case of THP or something(hdd swap
but tries THP swapout) *caller* rather than add_to_swap itself should
split the THP page and retry it with base page which is more natural.

Link: http://lkml.kernel.org/r/20170515112522.32457-4-ying.huang@intel.com
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 17 deletions

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 0ad214d7a7ad..9c71b6b2562f 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -184,7 +184,7 @@ void __delete_from_swap_cache(struct page *page)
  * Allocate swap space for the page and add the page to the
  * swap cache.  Caller needs to hold the page lock. 
  */
-int add_to_swap(struct page *page, struct list_head *list)
+int add_to_swap(struct page *page)
 {
         swp_entry_t entry;
         int err;
@@ -192,12 +192,12 @@ int add_to_swap(struct page *page, struct list_head *list)
         VM_BUG_ON_PAGE(!PageLocked(page), page);
         VM_BUG_ON_PAGE(!PageUptodate(page), page);
 
-retry:
         entry = get_swap_page(page);
         if (!entry.val)
-                goto fail;
+                return 0;
+
         if (mem_cgroup_try_charge_swap(page, entry))
-                goto fail_free;
+                goto fail;
 
         /*
          * Radix-tree node allocations from PF_MEMALLOC contexts could
@@ -218,23 +218,12 @@ retry:
                  * add_to_swap_cache() doesn't return -EEXIST, so we can safely
                  * clear SWAP_HAS_CACHE flag.
                  */
-                goto fail_free;
-
-        if (PageTransHuge(page)) {
-                err = split_huge_page_to_list(page, list);
-                if (err) {
-                        delete_from_swap_cache(page);
-                        return 0;
-                }
-        }
+                goto fail;
 
         return 1;
 
-fail_free:
-        put_swap_page(page, entry);
 fail:
-        if (PageTransHuge(page) && !split_huge_page_to_list(page, list))
-                goto retry;
+        put_swap_page(page, entry);
         return 0;
 }