On Wed, Mar 27, 2019 at 11:21:58AM -0700, Matthew Wilcox wrote: > On Wed, Mar 27, 2019 at 05:29:57PM +0000, Catalin Marinas wrote: > > On Wed, Mar 27, 2019 at 09:44:32AM +0100, Michal Hocko wrote: > > > As long as there is an implicit __GFP_NOFAIL then kmemleak is simply > > > broken no matter what other gfp flags you play with. Has anybody looked > > > at some sort of preallocation where gfpflags_allow_blocking context > > > allocate objects into a pool that non-sleeping allocations can eat from? > > > > Quick attempt below and it needs some more testing (pretty random pick > > of the EMERGENCY_POOL_SIZE value). Also, with __GFP_NOFAIL removed, are > > the other flags safe or we should trim them further? > > Why not use mempool?
I had the wrong impression that it could sleep but it's only if __GFP_DIRECT_RECLAIM is passed. See below for an updated patch. > > #define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \ > > __GFP_NORETRY | __GFP_NOMEMALLOC | \ > > - __GFP_NOWARN | __GFP_NOFAIL) > > + __GFP_NOWARN) > > Why GFP_NORETRY? And if I have specified one of the other retry policies > in my gfp flags, you should presumably clear that off before setting > GFP_NORETRY. It only preserves GFP_KERNEL|GFP_ATOMIC from the original flags while setting the NOWARN|NORETRY|NOMEMALLOC (the same flags seem to be set by mempool_alloc()). Anyway, with the changes below, I'll let mempool add the relevant flags while kmemleak only passes GFP_KERNEL|GFP_ATOMIC from the original caller. -----------------------8<------------------------------------------ >From 09eba8f0235eb16409931e6aad77a45a12bedc82 Mon Sep 17 00:00:00 2001 From: Catalin Marinas <[email protected]> Date: Thu, 28 Mar 2019 13:26:07 +0000 Subject: [PATCH] mm: kmemleak: Use mempool allocations for kmemleak objects This patch adds mempool allocations for struct kmemleak_object and kmemleak_scan_area as slightly more resilient than kmem_cache_alloc() under memory pressure. The patch also masks out all the gfp flags passed to kmemleak other than GFP_KERNEL|GFP_ATOMIC. Suggested-by: Michal Hocko <[email protected]> Signed-off-by: Catalin Marinas <[email protected]> --- mm/kmemleak.c | 34 +++++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 6c318f5ac234..9755678e83b9 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -82,6 +82,7 @@ #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> @@ -125,9 +126,7 @@ #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 | __GFP_NOFAIL) +#define gfp_kmemleak_mask(gfp) ((gfp) & (GFP_KERNEL | GFP_ATOMIC)) /* scanning area inside a memory block */ struct kmemleak_scan_area { @@ -191,6 +190,9 @@ struct kmemleak_object { #define HEX_ASCII 1 /* max number of lines to be printed */ #define HEX_MAX_LINES 2 +/* minimum memory pool sizes */ +#define MIN_OBJECT_POOL (NR_CPUS * 4) +#define MIN_SCAN_AREA_POOL (NR_CPUS * 1) /* the list of all allocated objects */ static LIST_HEAD(object_list); @@ -203,7 +205,9 @@ 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; /* set if tracing memory operations is enabled */ static int kmemleak_enabled; @@ -483,9 +487,9 @@ 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); } /* @@ -576,7 +580,7 @@ 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(); @@ -640,7 +644,7 @@ 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; } @@ -798,7 +802,7 @@ 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; @@ -810,7 +814,7 @@ 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; } @@ -2049,6 +2053,18 @@ 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",
