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From:   Vlastimil Babka <vbabka@suse.cz>
To:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Mel Gorman <mgorman@techsingularity.net>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Jann Horn <jannh@google.com>, Vlastimil Babka <vbabka@suse.cz>
Subject: [RFC 07/26] mm, slub: return slab page from get_partial() and set c->page afterwards
Date:   Tue, 25 May 2021 01:39:27 +0200
Message-Id: <20210524233946.20352-8-vbabka@suse.cz>
In-Reply-To: <20210524233946.20352-1-vbabka@suse.cz>
References: <20210524233946.20352-1-vbabka@suse.cz>
MIME-Version: 1.0
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Precedence: bulk

The function get_partial() finds a suitable page on a partial list, acquires
and returns its freelist and assigns the page pointer to kmem_cache_node.
In later patch we will need more control over the kmem_cache_node assignment,
so instead return the page pointer to get_partial()'s caller and assign it
there. No functional change as all of this still happens with disabled irq.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slub.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 9d1d872f5ab9..f240e424c861 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1971,7 +1971,7 @@ static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags);
  * Try to allocate a partial slab from a specific node.
  */
 static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
-				struct kmem_cache_cpu *c, gfp_t flags)
+			      struct page **ret_page, gfp_t flags)
 {
 	struct page *page, *page2;
 	void *object = NULL;
@@ -2000,7 +2000,7 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
 
 		available += objects;
 		if (!object) {
-			c->page = page;
+			*ret_page = page;
 			stat(s, ALLOC_FROM_PARTIAL);
 			object = t;
 		} else {
@@ -2020,7 +2020,7 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
  * Get a page from somewhere. Search in increasing NUMA distances.
  */
 static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
-		struct kmem_cache_cpu *c)
+			     struct page **ret_page)
 {
 #ifdef CONFIG_NUMA
 	struct zonelist *zonelist;
@@ -2062,7 +2062,7 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
 
 			if (n && cpuset_zone_allowed(zone, flags) &&
 					n->nr_partial > s->min_partial) {
-				object = get_partial_node(s, n, c, flags);
+				object = get_partial_node(s, n, ret_page, flags);
 				if (object) {
 					/*
 					 * Don't check read_mems_allowed_retry()
@@ -2084,7 +2084,7 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
  * Get a partial page, lock it and return it.
  */
 static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
-		struct kmem_cache_cpu *c)
+			 struct page **ret_page)
 {
 	void *object;
 	int searchnode = node;
@@ -2092,11 +2092,11 @@ static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
 	if (node == NUMA_NO_NODE)
 		searchnode = numa_mem_id();
 
-	object = get_partial_node(s, get_node(s, searchnode), c, flags);
+	object = get_partial_node(s, get_node(s, searchnode), ret_page, flags);
 	if (object || node != NUMA_NO_NODE)
 		return object;
 
-	return get_any_partial(s, flags, c);
+	return get_any_partial(s, flags, ret_page);
 }
 
 #ifdef CONFIG_PREEMPTION
@@ -2715,9 +2715,11 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 		goto redo;
 	}
 
-	freelist = get_partial(s, gfpflags, node, c);
-	if (freelist)
+	freelist = get_partial(s, gfpflags, node, &page);
+	if (freelist) {
+		c->page = page;
 		goto check_new_page;
+	}
 
 	page = new_slab(s, gfpflags, node);
 
@@ -2741,7 +2743,6 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	c->page = page;
 
 check_new_page:
-	page = c->page;
 	if (likely(!kmem_cache_debug(s) && pfmemalloc_match(page, gfpflags)))
 		goto load_freelist;
 
-- 
2.31.1