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Subject[PATCH v2] mm: kmemleak: Use mempool allocations for kmemleak objects
Date
Add mempool allocations for struct kmemleak_object and
kmemleak_scan_area as slightly more resilient than kmem_cache_alloc()
under memory pressure. Additionally, mask out all the gfp flags passed
to kmemleak other than GFP_KERNEL|GFP_ATOMIC.

A boot-time tuning parameter (kmemleak.mempool) is added to allow a
different minimum pool size (defaulting to NR_CPUS * 4).

Cc: Michal Hocko <mhocko@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Qian Cai <cai@lca.pw>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

v1 posted here:

http://lkml.kernel.org/r/20190328145917.GC10283@arrakis.emea.arm.com

Changes in v2:

- kmemleak.mempool cmdline parameter to configure the minimum pool size
- rebased against -next (on top of the __GFP_NOFAIL revert)

.../admin-guide/kernel-parameters.txt | 6 ++
mm/kmemleak.c | 58 +++++++++++++++----
2 files changed, 54 insertions(+), 10 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 46b826fcb5ad..11c413e3c42b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2011,6 +2011,12 @@
Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
the default is off.

+ kmemleak.mempool=
+ [KNL] Boot-time tuning of the minimum kmemleak
+ metadata pool size.
+ Format: <int>
+ Default: NR_CPUS * 4
+
kprobe_event=[probe-list]
[FTRACE] Add kprobe events and enable at boot time.
The probe-list is a semicolon delimited list of probe
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 6e9e8cca663e..a31eab79bcf5 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -69,6 +69,7 @@
#include <linux/kthread.h>
#include <linux/rbtree.h>
#include <linux/fs.h>
+#include <linux/mempool.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/cpumask.h>
@@ -112,9 +113,7 @@
#define BYTES_PER_POINTER sizeof(void *)

/* GFP bitmask for kmemleak internal allocations */
-#define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \
- __GFP_NORETRY | __GFP_NOMEMALLOC | \
- __GFP_NOWARN)
+#define gfp_kmemleak_mask(gfp) ((gfp) & (GFP_KERNEL | GFP_ATOMIC))

/* scanning area inside a memory block */
struct kmemleak_scan_area {
@@ -190,7 +189,13 @@ static DEFINE_RWLOCK(kmemleak_lock);

/* allocation caches for kmemleak internal data */
static struct kmem_cache *object_cache;
+static mempool_t *object_mempool;
static struct kmem_cache *scan_area_cache;
+static mempool_t *scan_area_mempool;
+
+/* default minimum memory pool sizes */
+static int min_object_pool = NR_CPUS * 4;
+static int min_scan_area_pool = NR_CPUS * 1;

/* set if tracing memory operations is enabled */
static int kmemleak_enabled;
@@ -465,9 +470,9 @@ static void free_object_rcu(struct rcu_head *rcu)
*/
hlist_for_each_entry_safe(area, tmp, &object->area_list, node) {
hlist_del(&area->node);
- kmem_cache_free(scan_area_cache, area);
+ mempool_free(area, scan_area_mempool);
}
- kmem_cache_free(object_cache, object);
+ mempool_free(object, object_mempool);
}

/*
@@ -550,7 +555,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
struct rb_node **link, *rb_parent;
unsigned long untagged_ptr;

- object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
+ object = mempool_alloc(object_mempool, gfp_kmemleak_mask(gfp));
if (!object) {
pr_warn("Cannot allocate a kmemleak_object structure\n");
kmemleak_disable();
@@ -614,7 +619,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
* be freed while the kmemleak_lock is held.
*/
dump_object_info(parent);
- kmem_cache_free(object_cache, object);
+ mempool_free(object, object_mempool);
object = NULL;
goto out;
}
@@ -772,7 +777,7 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
return;
}

- area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
+ area = mempool_alloc(scan_area_mempool, gfp_kmemleak_mask(gfp));
if (!area) {
pr_warn("Cannot allocate a scan area\n");
goto out;
@@ -784,7 +789,7 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
} else if (ptr + size > object->pointer + object->size) {
kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
dump_object_info(object);
- kmem_cache_free(scan_area_cache, area);
+ mempool_free(area, scan_area_mempool);
goto out_unlock;
}

@@ -1993,6 +1998,27 @@ static int __init kmemleak_boot_config(char *str)
}
early_param("kmemleak", kmemleak_boot_config);

+/*
+ * Allow boot-time tuning of the kmemleak mempool size.
+ */
+static int __init kmemleak_mempool_config(char *str)
+{
+ int size, ret;
+
+ if (!str)
+ return -EINVAL;
+
+ ret = kstrtoint(str, 0, &size);
+ if (ret)
+ return ret;
+
+ min_object_pool = size;
+ min_scan_area_pool = size / 4;
+
+ return 0;
+}
+early_param("kmemleak.mempool", kmemleak_mempool_config);
+
static void __init print_log_trace(struct early_log *log)
{
pr_notice("Early log backtrace:\n");
@@ -2020,6 +2046,18 @@ void __init kmemleak_init(void)

object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
+ if (!object_cache || !scan_area_cache) {
+ kmemleak_disable();
+ return;
+ }
+ object_mempool = mempool_create_slab_pool(min_object_pool,
+ object_cache);
+ scan_area_mempool = mempool_create_slab_pool(min_scan_area_pool,
+ scan_area_cache);
+ if (!object_mempool || !scan_area_mempool) {
+ kmemleak_disable();
+ return;
+ }

if (crt_early_log > ARRAY_SIZE(early_log))
pr_warn("Early log buffer exceeded (%d), please increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n",
@@ -2126,7 +2164,7 @@ static int __init kmemleak_late_init(void)
mutex_unlock(&scan_mutex);
}

- pr_info("Kernel memory leak detector initialized\n");
+ pr_info("Kernel memory leak detector initialized (mempool size: %d)\n", min_object_pool);

return 0;
}
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