[Devel] [PATCH RHEL8 COMMIT] ve/memcg: Account some swapped memory as used in CT in /proc/meminfo

[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.vz8.5.43
------>
commit 07bc4e8af16f5f1ce5da1b0a45fcab561ff4d797
Author: Andrey Ryabinin <aryabinin at virtuozzo.com>
Date:   Tue Mar 31 18:45:02 2020 +0300

    ve/memcg: Account some swapped memory as used in CT in /proc/meminfo
    
    If swapped memory of container exceed CT's swap size (can happen
    on external memory pressure) it's unaccounted in /proc/meminfo.
    
    Fix this by adding swapped above swap size to used counter.
    Ideally we should also add this to inactive anon and/or shmem, but
    we don't really know what was swapped, so leave it as is.
    
    https://jira.sw.ru/browse/PSBM-102266
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
    
    (The logic is taken from vz7 commit 9667cb8cbee3 ("memcg, bc/vm_pages.c:
    account some swapped memory as used in CT in /proc/meminfo"))
    
    Rebased in the scope of https://jira.sw.ru/browse/PSBM-127850.
    
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 fs/proc/meminfo.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 91797e63ad32..04ad51a4a698 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -90,24 +90,29 @@ void si_meminfo_ve(struct sysinfo *si, struct ve_struct *ve)
 	css = ve_get_init_css(ve, memory_cgrp_id);
 	memcg = mem_cgroup_from_css(css);
 
+	si->sharedram = memcg_page_state(memcg, NR_SHMEM);
+
 	memtotal = READ_ONCE(memcg->memory.max);
 	memused = page_counter_read(&memcg->memory);
 	si->totalram = memtotal;
-	si->freeram = (memtotal > memused ? memtotal - memused : 0);
-
-	si->sharedram = memcg_page_state(memcg, NR_SHMEM);
 
 	swaptotal = READ_ONCE(memcg->memsw.max) - memtotal;
 	swapused = page_counter_read(&memcg->memsw) - memused;
 	si->totalswap = swaptotal;
+
 	/* Due to global reclaim, memory.memsw.usage can be greater than
 	 * (memory.memsw.max - memory.max). */
-	si->freeswap = (swaptotal > swapused ? swaptotal - swapused : 0);
+	if (swaptotal >= swapused) {
+		si->freeswap = swaptotal - swapused;
+	} else {
+		si->freeswap = 0;
+		memused += swapused - swaptotal;
+	}
 
+	si->freeram = (memtotal > memused ? memtotal - memused : 0);
 	si->mem_unit = PAGE_SIZE;
 
 	css_put(css);
-
 	/* bufferram, totalhigh and freehigh left 0 */
 }