mm, swap_cgroup: reschedule when neeed in swap_cgroup_swapoff()

We got need_resched() warnings in swap_cgroup_swapoff() because
swap_cgroup_ctrl[type].length is particularly large.

Reschedule when needed.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1704061315270.80559@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/swap_cgroup.c b/mm/swap_cgroup.c
index 310ac0b8f974..ac6318a064d3 100644
--- a/mm/swap_cgroup.c
+++ b/mm/swap_cgroup.c
@@ -201,6 +201,8 @@ void swap_cgroup_swapoff(int type)
                         struct page *page = map[i];
                         if (page)
                                 __free_page(page);
+                        if (!(i % SWAP_CLUSTER_MAX))
+                                cond_resched();
                 }
                 vfree(map);
         }