mm/slab: Add kvfree_atomic() helper

kvmalloc() now supports non-sleeping GFP flags, including
the vmalloc fallback path. This means it may return vmalloc
memory even for GFP_ATOMIC and GFP_NOWAIT allocations.

Freeing such memory with kvfree() may then end up calling
vfree(), which is not safe for non-sleeping contexts.

Introduce kvfree_atomic() helper for such cases. It mirrors
kvfree(), but uses vfree_atomic() for vmalloced memory.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Acked-by: Harry Yoo (Oracle) <harry@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 15a60b501b95b6c3f5b7099f4aab67689be312ab..2b5ab488e96b07102660747c11b560ceb675e159 100644 (file)
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -1234,6 +1234,9 @@ void *kvrealloc_node_align_noprof(const void *p, size_t size, unsigned long alig
 extern void kvfree(const void *addr);
 DEFINE_FREE(kvfree, void *, if (!IS_ERR_OR_NULL(_T)) kvfree(_T))
 
+extern void kvfree_atomic(const void *addr);
+DEFINE_FREE(kvfree_atomic, void *, if (!IS_ERR_OR_NULL(_T)) kvfree_atomic(_T))
+
 extern void kvfree_sensitive(const void *addr, size_t len);
 
 unsigned int kmem_cache_size(struct kmem_cache *s);

diff --git a/mm/slub.c b/mm/slub.c
index 0baa906f39ab840fa79bf7f3744d5deac8891ca8..8f900453672968469460be9027758c5a8b2b8444 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -6882,6 +6882,22 @@ void kvfree(const void *addr)
 }
 EXPORT_SYMBOL(kvfree);
 
+/**
+ * kvfree_atomic() - Free memory.
+ * @addr: Pointer to allocated memory.
+ *
+ * Same as kvfree(), but uses vfree_atomic() for vmalloc
+ * backed memory. Must not be called from NMI context.
+ */
+void kvfree_atomic(const void *addr)
+{
+       if (is_vmalloc_addr(addr))
+               vfree_atomic(addr);
+       else
+               kfree(addr);
+}
+EXPORT_SYMBOL(kvfree_atomic);
+
 /**
  * kvfree_sensitive - Free a data object containing sensitive information.
  * @addr: address of the data object to be freed.