[PATCH v3 12/15] mm/slab: allow __GFP_NOMEMALLOC and __GFP_NOWARN for kmalloc_nolock()

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

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>
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 include/linux/slab.h |  3 ++-
 mm/slub.c            | 19 ++++++++++---------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index ce1c867dc0ba..b955f3cbb732 100644
--- 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 537ea68f417b..8769083bec81 100644
--- 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 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 		 */
 		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 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 	 * 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 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 		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 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 
 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);

-- 
2.54.0