mempool: introduce mempool_use_prealloc_only

Introduce a new mempool_alloc_preallocated API that asks the mempool to
only use the elements preallocated during the mempool's creation when
allocating and to not attempt allocating new ones from the underlying
allocator.

This API is required to test the KASAN poisoning/unpoisoning functionality
in KASAN tests, but it might be also useful on its own.

Link: https://lkml.kernel.org/r/a14d809dbdfd04cc33bcacc632fee2abd6b83c00.1703024586.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Lobakin <alobakin@pm.me>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/mempool.h b/include/linux/mempool.h
index 4aae6c06c5f283d4abbcf213b309f834af0f03e0..7be1e32e6d421d8003fb6466679e6fc7729f5c7d 100644 (file)
--- a/include/linux/mempool.h
+++ b/include/linux/mempool.h
@@ -51,6 +51,7 @@ extern mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
 extern int mempool_resize(mempool_t *pool, int new_min_nr);
 extern void mempool_destroy(mempool_t *pool);
 extern void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask) __malloc;
+extern void *mempool_alloc_preallocated(mempool_t *pool) __malloc;
 extern void mempool_free(void *element, mempool_t *pool);
 
 /*

diff --git a/mm/mempool.c b/mm/mempool.c
index 103dc4770cfb75a46a82e9c3ce81c8c00d5055dc..cb7b4b56cec1e5db78e6761e1413d4ecd83a6451 100644 (file)
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -456,6 +456,43 @@ repeat_alloc:
 }
 EXPORT_SYMBOL(mempool_alloc);
 
+/**
+ * mempool_alloc_preallocated - allocate an element from preallocated elements
+ *                              belonging to a specific memory pool
+ * @pool:      pointer to the memory pool which was allocated via
+ *             mempool_create().
+ *
+ * This function is similar to mempool_alloc, but it only attempts allocating
+ * an element from the preallocated elements. It does not sleep and immediately
+ * returns if no preallocated elements are available.
+ *
+ * Return: pointer to the allocated element or %NULL if no elements are
+ * available.
+ */
+void *mempool_alloc_preallocated(mempool_t *pool)
+{
+       void *element;
+       unsigned long flags;
+
+       spin_lock_irqsave(&pool->lock, flags);
+       if (likely(pool->curr_nr)) {
+               element = remove_element(pool);
+               spin_unlock_irqrestore(&pool->lock, flags);
+               /* paired with rmb in mempool_free(), read comment there */
+               smp_wmb();
+               /*
+                * Update the allocation stack trace as this is more useful
+                * for debugging.
+                */
+               kmemleak_update_trace(element);
+               return element;
+       }
+       spin_unlock_irqrestore(&pool->lock, flags);
+
+       return NULL;
+}
+EXPORT_SYMBOL(mempool_alloc_preallocated);
+
 /**
  * mempool_free - return an element to the pool.
  * @element:   pool element pointer.