mm, mempool: poison elements backed by page allocator

Elements backed by the slab allocator are poisoned when added to a
mempool's reserved pool.

It is also possible to poison elements backed by the page allocator
because the mempool layer knows the allocation order.

This patch extends mempool element poisoning to include memory backed by
the page allocator.

This is only effective for configs with CONFIG_DEBUG_SLAB or
CONFIG_SLUB_DEBUG_ON.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mempool.c b/mm/mempool.c
index 13336e7ae332fb6ce0e8e9dfdc6c2b577afc9935..436628dcf5c726b54d0bde0defbf9962009b0ee9 100644 (file)
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -6,6 +6,7 @@
  *  extreme VM load.
  *
  *  started by Ingo Molnar, Copyright (C) 2001
+ *  debugging by David Rientjes, Copyright (C) 2015
  */
 
 #include <linux/mm.h>
@@ -35,41 +36,64 @@ static void poison_error(mempool_t *pool, void *element, size_t size,
        dump_stack();
 }
 
-static void check_slab_element(mempool_t *pool, void *element)
+static void __check_element(mempool_t *pool, void *element, size_t size)
 {
-       if (pool->free == mempool_free_slab || pool->free == mempool_kfree) {
-               size_t size = ksize(element);
-               u8 *obj = element;
-               size_t i;
-
-               for (i = 0; i < size; i++) {
-                       u8 exp = (i < size - 1) ? POISON_FREE : POISON_END;
-
-                       if (obj[i] != exp) {
-                               poison_error(pool, element, size, i);
-                               return;
-                       }
+       u8 *obj = element;
+       size_t i;
+
+       for (i = 0; i < size; i++) {
+               u8 exp = (i < size - 1) ? POISON_FREE : POISON_END;
+
+               if (obj[i] != exp) {
+                       poison_error(pool, element, size, i);
+                       return;
                }
-               memset(obj, POISON_INUSE, size);
+       }
+       memset(obj, POISON_INUSE, size);
+}
+
+static void check_element(mempool_t *pool, void *element)
+{
+       /* Mempools backed by slab allocator */
+       if (pool->free == mempool_free_slab || pool->free == mempool_kfree)
+               __check_element(pool, element, ksize(element));
+
+       /* Mempools backed by page allocator */
+       if (pool->free == mempool_free_pages) {
+               int order = (int)(long)pool->pool_data;
+               void *addr = page_address(element);
+
+               __check_element(pool, addr, 1UL << (PAGE_SHIFT + order));
        }
 }
 
-static void poison_slab_element(mempool_t *pool, void *element)
+static void __poison_element(void *element, size_t size)
 {
-       if (pool->alloc == mempool_alloc_slab ||
-           pool->alloc == mempool_kmalloc) {
-               size_t size = ksize(element);
-               u8 *obj = element;
+       u8 *obj = element;
+
+       memset(obj, POISON_FREE, size - 1);
+       obj[size - 1] = POISON_END;
+}
+
+static void poison_element(mempool_t *pool, void *element)
+{
+       /* Mempools backed by slab allocator */
+       if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
+               __poison_element(element, ksize(element));
+
+       /* Mempools backed by page allocator */
+       if (pool->alloc == mempool_alloc_pages) {
+               int order = (int)(long)pool->pool_data;
+               void *addr = page_address(element);
 
-               memset(obj, POISON_FREE, size - 1);
-               obj[size - 1] = POISON_END;
+               __poison_element(addr, 1UL << (PAGE_SHIFT + order));
        }
 }
 #else /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */
-static inline void check_slab_element(mempool_t *pool, void *element)
+static inline void check_element(mempool_t *pool, void *element)
 {
 }
-static inline void poison_slab_element(mempool_t *pool, void *element)
+static inline void poison_element(mempool_t *pool, void *element)
 {
 }
 #endif /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */
@@ -77,7 +101,7 @@ static inline void poison_slab_element(mempool_t *pool, void *element)
 static void add_element(mempool_t *pool, void *element)
 {
        BUG_ON(pool->curr_nr >= pool->min_nr);
-       poison_slab_element(pool, element);
+       poison_element(pool, element);
        pool->elements[pool->curr_nr++] = element;
 }
 
@@ -86,7 +110,7 @@ static void *remove_element(mempool_t *pool)
        void *element = pool->elements[--pool->curr_nr];
 
        BUG_ON(pool->curr_nr < 0);
-       check_slab_element(pool, element);
+       check_element(pool, element);
        return element;
 }