linux-kernel - [PATCH v4 09/35] mm, slub: return slab page from get

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Date:   Thu,  5 Aug 2021 17:19:34 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Mike Galbraith <efault@....de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Jann Horn <jannh@...gle.com>, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v4 09/35] mm, slub: return slab page from get_partial() and set c->page afterwards

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_cpu.
In later patch we will need more control over the kmem_cache_cpu.page
assignment, so instead of passing a kmem_cache_cpu pointer, pass a pointer to a
pointer to a page that get_partial() can fill and the caller can assign the
kmem_cache_cpu.page pointer. No functional change as all of this still happens
with disabled IRQs.

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

diff --git a/mm/slub.c b/mm/slub.c
index 3222ea51fb50..ed18fa3157ad 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2000,7 +2000,7 @@ 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;
@@ -2029,7 +2029,7 @@ 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 {
@@ -2049,7 +2049,7 @@ 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;
@@ -2091,7 +2091,7 @@ 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()
@@ -2113,7 +2113,7 @@ 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;
@@ -2121,11 +2121,11 @@ 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
@@ -2737,9 +2737,11 @@ 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);
 
@@ -2763,7 +2765,6 @@ 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;
 
-- 
2.32.0