memcg, THP, swap: support move mem cgroup charge for THP swapped out

PTE mapped THP (Transparent Huge Page) will be ignored when moving
memory cgroup charge.  But for THP which is in the swap cache, the
memory cgroup charge for the swap of a tail-page may be moved in current
implementation.  That isn't correct, because the swap charge for all
sub-pages of a THP should be moved together.  Following the processing
of the PTE mapped THP, the mem cgroup charge moving for the swap entry
for a tail-page of a THP is ignored too.

Link: http://lkml.kernel.org/r/20170724051840.2309-9-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c]
Cc: Shaohua Li <shli@kernel.org>
Cc: Vishal L Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3d3f7b1686acb5b0363326dca51a715bf773fb6a..2ae315e4d9f6df4028173b16afce8b668263a2a7 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4639,8 +4639,11 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
                if (!ret || !target)
                        put_page(page);
        }
-       /* There is a swap entry and a page doesn't exist or isn't charged */
-       if (ent.val && !ret &&
+       /*
+        * There is a swap entry and a page doesn't exist or isn't charged.
+        * But we cannot move a tail-page in a THP.
+        */
+       if (ent.val && !ret && (!page || !PageTransCompound(page)) &&
            mem_cgroup_id(mc.from) == lookup_swap_cgroup_id(ent)) {
                ret = MC_TARGET_SWAP;
                if (target)