mm/slab: allow __GFP_NOMEMALLOC and __GFP_NOWARN for kmalloc_nolock()

The two flags are added internally so there's no point for warning if
they are passed by the caller as well, so allow them. This will allow
simplifying obj_ext allocation under kmalloc_nolock().

Also it's not necessary to have the extra alloc_gfp variable for adding
the two flags. The original gfp_flags parameter is not used anywhere
except for the warning. So remove alloc_gfp and directly modify and use
gfp_flags everywhere.

Link: https://patch.msgid.link/20260610-slab_alloc_flags-v2-13-7190909db118@kernel.org
Reviewed-by: Hao Li <hao.li@linux.dev>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Harry Yoo (Oracle) <harry@kernel.org>
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

diff --git a/include/linux/slab.h b/include/linux/slab.h
index ce1c867dc0ba8b65f46707c3ff99465c1dcc4e32..b955f3cbb7328f4ec75758b8424a388b57df78c5 100644 (file)
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -1040,7 +1040,8 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
  * kmalloc_nolock - Allocate an object of given size from any context.
  * @size: size to allocate
  * @gfp_flags: GFP flags. Only __GFP_ACCOUNT, __GFP_ZERO, __GFP_NO_OBJ_EXT
- * allowed.
+ * allowed. Also __GFP_NOWARN and __GFP_NOMEMALLOC are allowed but added
+ * internally thus not necessary.
  * @node: node number of the target node.
  *
  * Return: pointer to the new object or NULL in case of error.

diff --git a/mm/slub.c b/mm/slub.c
index 537ea68f417b40cd56d79722e7bd044a963b5ad7..8769083bec8180a19494385d2b6be852ee667b54 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5387,7 +5387,6 @@ EXPORT_SYMBOL(__kmalloc_noprof);
 
 void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, int node)
 {
-       gfp_t alloc_gfp = __GFP_NOWARN | __GFP_NOMEMALLOC | gfp_flags;
        size_t orig_size = size;
        unsigned int alloc_flags = SLAB_ALLOC_NOLOCK;
        struct kmem_cache *s;
@@ -5400,7 +5399,9 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
        };
 
        VM_WARN_ON_ONCE(gfp_flags & ~(__GFP_ACCOUNT | __GFP_ZERO |
-                                     __GFP_NO_OBJ_EXT));
+                       __GFP_NO_OBJ_EXT | __GFP_NOWARN | __GFP_NOMEMALLOC));
+
+       gfp_flags |= __GFP_NOWARN | __GFP_NOMEMALLOC;
 
        if (unlikely(!size))
                return ZERO_SIZE_PTR;
@@ -5419,7 +5420,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 retry:
        if (unlikely(size > KMALLOC_MAX_CACHE_SIZE))
                return NULL;
-       s = kmalloc_slab(size, NULL, alloc_gfp, PASS_TOKEN_PARAM(token));
+       s = kmalloc_slab(size, NULL, gfp_flags, PASS_TOKEN_PARAM(token));
 
        if (!(s->flags & __CMPXCHG_DOUBLE) && !kmem_cache_debug(s))
                /*
@@ -5433,7 +5434,7 @@ retry:
                 */
                return NULL;
 
-       ret = alloc_from_pcs(s, alloc_gfp, alloc_flags, node);
+       ret = alloc_from_pcs(s, gfp_flags, alloc_flags, node);
        if (ret)
                goto success;
 
@@ -5443,7 +5444,7 @@ retry:
         * kfence_alloc. Hence call __slab_alloc_node() (at most twice)
         * and slab_post_alloc_hook() directly.
         */
-       ret = __slab_alloc_node(s, alloc_gfp, node, &ac);
+       ret = __slab_alloc_node(s, gfp_flags, node, &ac);
 
        /*
         * It's possible we failed due to trylock as we preempted someone with
@@ -5456,8 +5457,8 @@ retry:
                size = s->object_size + 1;
                /*
                 * Another alternative is to
-                * if (memcg) alloc_gfp &= ~__GFP_ACCOUNT;
-                * else if (!memcg) alloc_gfp |= __GFP_ACCOUNT;
+                * if (memcg) gfp_flags &= ~__GFP_ACCOUNT;
+                * else if (!memcg) gfp_flags |= __GFP_ACCOUNT;
                 * to retry from bucket of the same size.
                 */
                can_retry = false;
@@ -5466,9 +5467,9 @@ retry:
 
 success:
        maybe_wipe_obj_freeptr(s, ret);
-       slab_post_alloc_hook(s, alloc_gfp, 1, &ret, &ac);
+       slab_post_alloc_hook(s, gfp_flags, 1, &ret, &ac);
 
-       ret = kasan_kmalloc(s, ret, orig_size, alloc_gfp);
+       ret = kasan_kmalloc(s, ret, orig_size, gfp_flags);
        return ret;
 }
 EXPORT_SYMBOL_GPL(_kmalloc_nolock_noprof);