[Devel] [PATCH RHEL8 COMMIT] ve/memcg: Fix /proc/meminfo virtualization (eliminate double recursion)

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-240.1.1.vz8.5.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-240.1.1.vz8.5.60
------>
commit bdd06e3a5340b777d3b9bfabea676698e2e75b35
Author: Konstantin Khorenko <khorenko at virtuozzo.com>
Date:   Thu Jul 22 13:16:05 2021 +0300

    ve/memcg: Fix /proc/meminfo virtualization (eliminate double recursion)
    
    This patch partially reverts commit 47f1b6c1d8e5 ("ve/memcg: Make
    virtualization of /proc/meminfo view inside CT recursive")
    
    In vz8 we have both memcg->vmstats (recursive) and
    memcg->vmstats_local (non-recursive), and mem_page_state_recursive()
    brought by the reverted commit does double recursion,
    so revert that logic, but leave the other stuff.
    
    Fixes: 47f1b6c1d8e5 ("ve/memcg: Make virtualization of /proc/meminfo
    view inside CT recursive")
    
    To_merge: 38a2f168a441 ("ve/proc: virtualize /proc/meminfo in a Container")
    
    https://jira.sw.ru/browse/PSBM-131992
    
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 mm/memcontrol.c | 26 +++++++-------------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 85d521906bec..8d82bfd3f79a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3865,18 +3865,6 @@ void mem_cgroup_get_nr_pages(struct mem_cgroup *memcg, int nid,
 	}
 }
 
-static unsigned long mem_page_state_recursive(struct mem_cgroup *memcg,
-					      int idx)
-{
-	struct mem_cgroup *iter;
-	unsigned long val = 0;
-
-	for_each_mem_cgroup_tree(iter, memcg)
-		val += memcg_page_state(iter, idx);
-
-	return val;
-}
-
 void mem_cgroup_fill_meminfo(struct mem_cgroup *memcg, struct meminfo *mi)
 {
 	int nid;
@@ -3885,12 +3873,12 @@ void mem_cgroup_fill_meminfo(struct mem_cgroup *memcg, struct meminfo *mi)
 	for_each_online_node(nid)
 		mem_cgroup_get_nr_pages(memcg, nid, mi->pages);
 
-	mi->slab_reclaimable = mem_page_state_recursive(memcg, NR_SLAB_RECLAIMABLE);
-	mi->slab_unreclaimable = mem_page_state_recursive(memcg, NR_SLAB_UNRECLAIMABLE);
-	mi->cached = mem_page_state_recursive(memcg, MEMCG_CACHE);
-	mi->shmem = mem_page_state_recursive(memcg, NR_SHMEM);
-	mi->dirty_pages = mem_page_state_recursive(memcg, NR_FILE_DIRTY);
-	mi->writeback_pages = mem_page_state_recursive(memcg, NR_WRITEBACK);
+	mi->slab_reclaimable	= memcg_page_state(memcg, NR_SLAB_RECLAIMABLE);
+	mi->slab_unreclaimable	= memcg_page_state(memcg, NR_SLAB_UNRECLAIMABLE);
+	mi->cached		= memcg_page_state(memcg, MEMCG_CACHE);
+	mi->shmem		= memcg_page_state(memcg, NR_SHMEM);
+	mi->dirty_pages		= memcg_page_state(memcg, NR_FILE_DIRTY);
+	mi->writeback_pages	= memcg_page_state(memcg, NR_WRITEBACK);
 
 	/* locked pages are accounted per zone */
 	/* mi->locked = 0; */
@@ -3901,7 +3889,7 @@ void mem_cgroup_fill_meminfo(struct mem_cgroup *memcg, struct meminfo *mi)
 	 * are not taken into account. These values reflect reservation of
 	 * physycal memory and they are not relevant for CT.
 	 */
-	mi->available = mi->si->freeram;
+	mi->available  = mi->si->freeram;
 	mi->available += mi->pages[LRU_ACTIVE_FILE] +
 			 mi->pages[LRU_INACTIVE_FILE];
 	mi->available += mi->slab_reclaimable;