When force_empty() called by ->pre_destroy(), no memory reclaim happens
and it doesn't take very long time which requires signal_pending() check.
And if we return -EINTR from pre_destroy(), cgroup.c show warning.

This patch removes signal check in force_empty(). By this, ->pre_destroy()
returns success always.

Note: check for 'cgroup is empty' remains for force_empty interface.

Signed-off-by: KAMEZAWA Hiroyuki <redacted>
---
 mm/hugetlb.c    |   10 +---------
 mm/memcontrol.c |   14 +++++---------
 2 files changed, 6 insertions(+), 18 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4dd6b39..770f1642 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c

@@ -1922,20 +1922,12 @@ int hugetlb_force_memcg_empty(struct cgroup *cgroup)

       int ret = 0, idx = 0;

       do {
+               /* see memcontrol.c::mem_cgroup_force_empty() */
               if (cgroup_task_count(cgroup)
                       || !list_empty(&cgroup->children)) {
                       ret = -EBUSY;
                       goto out;
               }
-               /*
-                * If the task doing the cgroup_rmdir got a signal
-                * we don't really need to loop till the hugetlb resource
-                * usage become zero.
-                */
-               if (signal_pending(current)) {
-                       ret = -EINTR;
-                       goto out;
-               }
               for_each_hstate(h) {
                       spin_lock(&hugetlb_lock);
                       list_for_each_entry(page, &h->hugepage_activelist, lru) {

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2715223..ee350c5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -3852,8 +3852,6 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,

               pc = lookup_page_cgroup(page);

               ret = mem_cgroup_move_parent(page, pc, memcg, GFP_KERNEL);
-               if (ret == -ENOMEM || ret == -EINTR)
-                       break;

               if (ret == -EBUSY || ret == -EINVAL) {
                       /* found lock contention or "pc" is obsolete. */

@@ -3863,7 +3861,7 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,

                       busy = NULL;
       }

-       if (!ret && !list_empty(list))
+       if (!loop)
               return -EBUSY;
       return ret;
 }

@@ -3893,11 +3891,12 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg, bool free_all)

 move_account:
       do {
               ret = -EBUSY;
+               /*
+                * This never happens when this is called by ->pre_destroy().
+                * But we need to take care of force_empty interface.
+                */
               if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
                       goto out;