memcgroup: tidy up mem_cgroup_charge_common

Tidy up mem_cgroup_charge_common before extending it.  Adjust some comments,
but mainly clean up its loop: I've an aversion to loops full of continues,
then a break or a goto at the bottom.  And the is_atomic test should be on the
__GFP_WAIT bit, not GFP_ATOMIC bits.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
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 160101a05b4d6c7e510c674ea21522dc57ede667..dbf571547c0333f30f6cfdba07bced94f3bf5405 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -345,23 +345,22 @@ retry:
                        goto done;
                }
        }
-
        unlock_page_cgroup(page);
 
        pc = kzalloc(sizeof(struct page_cgroup), gfp_mask);
        if (pc == NULL)
                goto err;
 
-       rcu_read_lock();
        /*
-        * We always charge the cgroup the mm_struct belongs to
-        * the mm_struct's mem_cgroup changes on task migration if the
+        * We always charge the cgroup the mm_struct belongs to.
+        * The mm_struct's mem_cgroup changes on task migration if the
         * thread group leader migrates. It's possible that mm is not
         * set, if so charge the init_mm (happens for pagecache usage).
         */
        if (!mm)
                mm = &init_mm;
 
+       rcu_read_lock();
        mem = rcu_dereference(mm->mem_cgroup);
        /*
         * For every charge from the cgroup, increment reference
@@ -375,12 +374,8 @@ retry:
         * the cgroup limit.
         */
        while (res_counter_charge(&mem->res, PAGE_SIZE)) {
-               bool is_atomic = gfp_mask & GFP_ATOMIC;
-               /*
-                * We cannot reclaim under GFP_ATOMIC, fail the charge
-                */
-               if (is_atomic)
-                       goto noreclaim;
+               if (!(gfp_mask & __GFP_WAIT))
+                       goto out;
 
                if (try_to_free_mem_cgroup_pages(mem, gfp_mask))
                        continue;
@@ -394,23 +389,12 @@ retry:
                 */
                if (res_counter_check_under_limit(&mem->res))
                        continue;
-                       /*
-                        * Since we control both RSS and cache, we end up with a
-                        * very interesting scenario where we end up reclaiming
-                        * memory (essentially RSS), since the memory is pushed
-                        * to swap cache, we eventually end up adding those
-                        * pages back to our list. Hence we give ourselves a
-                        * few chances before we fail
-                        */
-               else if (nr_retries--) {
-                       congestion_wait(WRITE, HZ/10);
-                       continue;
+
+               if (!nr_retries--) {
+                       mem_cgroup_out_of_memory(mem, gfp_mask);
+                       goto out;
                }
-noreclaim:
-               css_put(&mem->css);
-               if (!is_atomic)
-                       mem_cgroup_out_of_memory(mem, GFP_KERNEL);
-               goto free_pc;
+               congestion_wait(WRITE, HZ/10);
        }
 
        atomic_set(&pc->ref_cnt, 1);
@@ -419,10 +403,11 @@ noreclaim:
        pc->flags = 0;
        if (ctype == MEM_CGROUP_CHARGE_TYPE_CACHE)
                pc->flags |= PAGE_CGROUP_FLAG_CACHE;
+
        if (page_cgroup_assign_new_page_cgroup(page, pc)) {
                /*
-                * an another charge is added to this page already.
-                * we do take lock_page_cgroup(page) again and read
+                * Another charge has been added to this page already.
+                * We take lock_page_cgroup(page) again and read
                 * page->cgroup, increment refcnt.... just retry is OK.
                 */
                res_counter_uncharge(&mem->res, PAGE_SIZE);
@@ -437,7 +422,8 @@ noreclaim:
 
 done:
        return 0;
-free_pc:
+out:
+       css_put(&mem->css);
        kfree(pc);
 err:
        return -ENOMEM;