Patch "memcg: fix thresholds for 32b architectures.

This is a note to let you know that I've just added the patch titled

memcg: fix thresholds for 32b architectures.
memcg: fix thresholds for 32b architectures.
memcg: fix thresholds for 32b architectures.

to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
memcg-fix-thresholds-for-32b-architectures.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Michal Hocko <[email protected]>
Date: Thu, 5 Nov 2015 18:50:29 -0800
Subject: memcg: fix thresholds for 32b architectures.

From: Michal Hocko <[email protected]>

commit c12176d3368b9b36ae484d323d41e94be26f9b65 upstream.

Commit 424cdc141380 ("memcg: convert threshold to bytes") has fixed a regression introduced by 3e32cb2e0a12 ("mm: memcontrol: lockless page counters") where thresholds were silently converted to use page units rather than bytes when interpreting the user input.

The fix is not complete, though, as properly pointed out by Ben Hutchings during stable backport review. The page count is converted to bytes but unsigned long is used to hold the value which would be obviously not sufficient for 32b systems with more than 4G thresholds. The same applies to usage as taken from mem_cgroup_usage which might overflow.

Let's remove this bytes vs. pages internal tracking differences and handle thresholds in page units internally. Chage mem_cgroup_usage() to return the value in page units and revert 424cdc141380 because this should be sufficient for the consistent handling. mem_cgroup_read_u64 as the only users of mem_cgroup_usage outside of the threshold handling code is converted to give the proper in bytes result. It is doing that already for page_counter output so this is more consistent as well.

The value presented to the userspace is still in bytes units.

From: Michal Hocko <[email protected]>
Subject: memcg: fix thresholds for 32b architectures.

Cc: Ben Hutchings <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Johannes Weiner <[email protected]>
From: Andrew Morton <[email protected]>
Subject: memcg: fix thresholds for 32b architectures.

don't attempt to inline mem_cgroup_usage()

The compiler ignores the inline anwyay. And __always_inlining it adds 600 bytes of goop to the .o file.

---
 mm/memcontrol.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

@@ -2836,9 +2836,9 @@ static unsigned long tree_stat(struct me
 	return val;
 }
 
-static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
+static inline unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
 {
-	u64 val;
+	unsigned long val;
 
 	if (mem_cgroup_is_root(memcg)) {
 		val = tree_stat(memcg, MEM_CGROUP_STAT_CACHE);

@@ -2851,7 +2851,7 @@ static inline u64 mem_cgroup_usage(struc
 		else
 			val = page_counter_read(&memcg->memsw);
 	}
-	return val << PAGE_SHIFT;
+	return val;
 }
 
 enum {

@@ -2885,9 +2885,9 @@ static u64 mem_cgroup_read_u64(struct cg
 	switch (MEMFILE_ATTR(cft->private)) {
 	case RES_USAGE:
 		if (counter == &memcg->memory)
-			return mem_cgroup_usage(memcg, false);
+			return (u64)mem_cgroup_usage(memcg, false) * PAGE_SIZE;
 		if (counter == &memcg->memsw)
-			return mem_cgroup_usage(memcg, true);
+			return (u64)mem_cgroup_usage(memcg, true) * PAGE_SIZE;
 		return (u64)page_counter_read(counter) * PAGE_SIZE;
 	case RES_LIMIT:
 		return (u64)counter->limit * PAGE_SIZE;

@@ -3387,7 +3387,6 @@ static int __mem_cgroup_usage_register_e
 	ret = page_counter_memparse(args, "-1", &threshold);
 	if (ret)
 		return ret;
-	threshold <<= PAGE_SHIFT;
 
 	mutex_lock(&memcg->thresholds_lock);
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.3/mm-oom_kill.c-reverse-the-order-of-setting-tif_memdie-and-sending-sigkill.patch queue-4.3/mm-vmstat-allow-wq-concurrency-to-discover-memory-reclaim-doesn-t-make-any-progress.patch queue-4.3/memcg-fix-thresholds-for-32b-architectures.patch