linux-kernel - [PATCH RFC v3 2/9] mm/slub: introduce __kmem_cache_free

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Date:   Wed, 29 Nov 2023 10:53:27 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, maple-tree@...ts.infradead.org,
        kasan-dev@...glegroups.com, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH RFC v3 2/9] mm/slub: introduce __kmem_cache_free_bulk()
 without free hooks

Currently, when __kmem_cache_alloc_bulk() fails, it frees back the
objects that were allocated before the failure, using
kmem_cache_free_bulk(). Because kmem_cache_free_bulk() calls the free
hooks (kasan etc.) and those expect objects processed by the post alloc
hooks, slab_post_alloc_hook() is called before kmem_cache_free_bulk().

This is wasteful, although not a big concern in practice for the very
rare error path. But in order to efficiently handle percpu array batch
refill and free in the following patch, we will also need a variant of
kmem_cache_free_bulk() that avoids the free hooks. So introduce it first
and use it in the error path too.

As a consequence, __kmem_cache_alloc_bulk() no longer needs the objcg
parameter, remove it.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index f0cd55bb4e11..16748aeada8f 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3919,6 +3919,27 @@ int build_detached_freelist(struct kmem_cache *s, size_t size,
 	return same;
 }
 
+/*
+ * Internal bulk free of objects that were not initialised by the post alloc
+ * hooks and thus should not be processed by the free hooks
+ */
+static void __kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
+{
+	if (!size)
+		return;
+
+	do {
+		struct detached_freelist df;
+
+		size = build_detached_freelist(s, size, p, &df);
+		if (!df.slab)
+			continue;
+
+		do_slab_free(df.s, df.slab, df.freelist, df.tail, df.cnt,
+			     _RET_IP_);
+	} while (likely(size));
+}
+
 /* Note that interrupts must be enabled when calling this function. */
 void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
 {
@@ -3940,7 +3961,7 @@ EXPORT_SYMBOL(kmem_cache_free_bulk);
 
 #ifndef CONFIG_SLUB_TINY
 static inline int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
-			size_t size, void **p, struct obj_cgroup *objcg)
+					  size_t size, void **p)
 {
 	struct kmem_cache_cpu *c;
 	unsigned long irqflags;
@@ -4004,14 +4025,13 @@ static inline int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
 
 error:
 	slub_put_cpu_ptr(s->cpu_slab);
-	slab_post_alloc_hook(s, objcg, flags, i, p, false, s->object_size);
-	kmem_cache_free_bulk(s, i, p);
+	__kmem_cache_free_bulk(s, i, p);
 	return 0;
 
 }
 #else /* CONFIG_SLUB_TINY */
 static int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
-			size_t size, void **p, struct obj_cgroup *objcg)
+				   size_t size, void **p)
 {
 	int i;
 
@@ -4034,8 +4054,7 @@ static int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
 	return i;
 
 error:
-	slab_post_alloc_hook(s, objcg, flags, i, p, false, s->object_size);
-	kmem_cache_free_bulk(s, i, p);
+	__kmem_cache_free_bulk(s, i, p);
 	return 0;
 }
 #endif /* CONFIG_SLUB_TINY */
@@ -4055,7 +4074,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
 	if (unlikely(!s))
 		return 0;
 
-	i = __kmem_cache_alloc_bulk(s, flags, size, p, objcg);
+	i = __kmem_cache_alloc_bulk(s, flags, size, p);
 
 	/*
 	 * memcg and kmem_cache debug support and memory initialization.

-- 
2.43.0