The patch titled
Subject: slub: consider pfmemalloc_match() in get_partial_node()
has been added to the -mm tree. Its filename is
slub-consider-pfmemalloc_match-in-get_partial_node.patch
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From: Joonsoo Kim <js1304@xxxxxxxxx>
Subject: slub: consider pfmemalloc_match() in get_partial_node()
get_partial() is currently not checking pfmemalloc_match() meaning that it
is possible for pfmemalloc pages to leak to non-pfmemalloc users. This is
a problem in the following situation. Assume that there is a request from
normal allocation and there are no objects in the per-cpu cache and no
node-partial slab.
In this case, slab_alloc enters the slow path and new_slab_objects() is
called which may return a PFMEMALLOC page. As the current user is not
allowed to access PFMEMALLOC page, deactivate_slab() is called ([5091b74a:
mm: slub: optimise the SLUB fast path to avoid pfmemalloc checks]) and
returns an object from PFMEMALLOC page.
Next time, when we get another request from normal allocation,
slab_alloc() enters the slow-path and calls new_slab_objects(). In
new_slab_objects(), we call get_partial() and get a partial slab which was
just deactivated but is a pfmemalloc page. We extract one object from it
and re-deactivate.
"deactivate -> re-get in get_partial -> re-deactivate" occures repeatedly.
As a result, access to PFMEMALLOC page is not properly restricted and it
can cause a performance degradation due to frequent deactivation.
deactivation frequently.
This patch changes get_partial_node() to take pfmemalloc_match() into
account and prevents the "deactivate -> re-get in get_partial() scenario.
Instead, new_slab() is called.
Signed-off-by: Joonsoo Kim <js1304@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff -puN mm/slub.c~slub-consider-pfmemalloc_match-in-get_partial_node mm/slub.c
--- a/mm/slub.c~slub-consider-pfmemalloc_match-in-get_partial_node
+++ a/mm/slub.c
@@ -1524,12 +1524,13 @@ static inline void *acquire_slab(struct
}
static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);
+static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags);
/*
* Try to allocate a partial slab from a specific node.
*/
-static void *get_partial_node(struct kmem_cache *s,
- struct kmem_cache_node *n, struct kmem_cache_cpu *c)
+static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
+ struct kmem_cache_cpu *c, gfp_t flags)
{
struct page *page, *page2;
void *object = NULL;
@@ -1545,9 +1546,13 @@ static void *get_partial_node(struct kme
spin_lock(&n->list_lock);
list_for_each_entry_safe(page, page2, &n->partial, lru) {
- void *t = acquire_slab(s, n, page, object == NULL);
+ void *t;
int available;
+ if (!pfmemalloc_match(page, flags))
+ continue;
+
+ t = acquire_slab(s, n, page, object == NULL);
if (!t)
break;
@@ -1614,7 +1619,7 @@ static void *get_any_partial(struct kmem
if (n && cpuset_zone_allowed_hardwall(zone, flags) &&
n->nr_partial > s->min_partial) {
- object = get_partial_node(s, n, c);
+ object = get_partial_node(s, n, c, flags);
if (object) {
/*
* Return the object even if
@@ -1643,7 +1648,7 @@ static void *get_partial(struct kmem_cac
void *object;
int searchnode = (node == NUMA_NO_NODE) ? numa_node_id() : node;
- object = get_partial_node(s, get_node(s, searchnode), c);
+ object = get_partial_node(s, get_node(s, searchnode), c, flags);
if (object || node != NUMA_NO_NODE)
return object;
_
Patches currently in -mm which might be from js1304@xxxxxxxxx are
slab-do-clearslabpfmemalloc-for-all-pages-of-slab.patch
slab-fix-starting-index-for-finding-another-object.patch
slub-consider-pfmemalloc_match-in-get_partial_node.patch
include-net-sockh-squelch-compiler-warning-in-sk_rmem_schedule.patch
linux-next.patch
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