The patch titled Subject: mm, slab: fix sign conversion problem in memcg_uncharge_slab() has been removed from the -mm tree. Its filename was mm-slab-fix-sign-conversion-problem-in-memcg_uncharge_slab.patch

This patch was dropped because it was merged into mainline or a subsystem tree

------------------------------------------------------ From: Waiman Long longman@redhat.com Subject: mm, slab: fix sign conversion problem in memcg_uncharge_slab()

It was found that running the LTP test on a PowerPC system could produce erroneous values in /proc/meminfo, like:

MemTotal: 531915072 kB MemFree: 507962176 kB MemAvailable: 1100020596352 kB

Using bisection, the problem is tracked down to commit 9c315e4d7d8c ("mm: memcg/slab: cache page number in memcg_(un)charge_slab()").

In memcg_uncharge_slab() with a "int order" argument:

unsigned int nr_pages = 1 << order; : mod_lruvec_state(lruvec, cache_vmstat_idx(s), -nr_pages);

The mod_lruvec_state() function will eventually call the __mod_zone_page_state() which accepts a long argument. Depending on the compiler and how inlining is done, "-nr_pages" may be treated as a negative number or a very large positive number. Apparently, it was treated as a large positive number in that PowerPC system leading to incorrect stat counts. This problem hasn't been seen in x86-64 yet, perhaps the gcc compiler there has some slight difference in behavior.

It is fixed by making nr_pages a signed value. For consistency, a similar change is applied to memcg_charge_slab() as well.

Link: http://lkml.kernel.org/r/20200620184719.10994-1-longman@redhat.com Fixes: 9c315e4d7d8c ("mm: memcg/slab: cache page number in memcg_(un)charge_slab()"). Signed-off-by: Waiman Long longman@redhat.com Acked-by: Roman Gushchin guro@fb.com Cc: Christoph Lameter cl@linux.com Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Shakeel Butt shakeelb@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/slab.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/slab.h~mm-slab-fix-sign-conversion-problem-in-memcg_uncharge_slab +++ a/mm/slab.h @@ -348,7 +348,7 @@ static __always_inline int memcg_charge_ gfp_t gfp, int order, struct kmem_cache *s) { - unsigned int nr_pages = 1 << order; + int nr_pages = 1 << order; struct mem_cgroup *memcg; struct lruvec *lruvec; int ret; @@ -388,7 +388,7 @@ out: static __always_inline void memcg_uncharge_slab(struct page *page, int order, struct kmem_cache *s) { - unsigned int nr_pages = 1 << order; + int nr_pages = 1 << order; struct mem_cgroup *memcg; struct lruvec *lruvec;

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Patches currently in -mm which might be from longman@redhat.com are

mm-treewide-rename-kzfree-to-kfree_sensitive.patch sched-mm-optimize-current_gfp_context.patch