[017/212] mm, slub: return slab page from get_partial() and set c->page afterwards

Commit Message

Andrew Morton Sept. 2, 2021, 9:50 p.m. UTC

From: Vlastimil Babka <[e-mail]>
Subject: 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.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Jesper Dangaard Brouer <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Cc: Sebastian Andrzej Siewior <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/slub.c |   21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

Patch

--- a/mm/slub.c~mm-slub-return-slab-page-from-get_partial-and-set-c-page-afterwards
+++ a/mm/slub.c
@@ -2003,7 +2003,7 @@  static inline bool pfmemalloc_match(stru
  * 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;
@@ -2032,7 +2032,7 @@  static void *get_partial_node(struct kme
 
 		available += objects;
 		if (!object) {
-			c->page = page;
+			*ret_page = page;
 			stat(s, ALLOC_FROM_PARTIAL);
 			object = t;
 		} else {
@@ -2052,7 +2052,7 @@  static void *get_partial_node(struct kme
  * 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;
@@ -2094,7 +2094,7 @@  static void *get_any_partial(struct kmem
 
 			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()
@@ -2116,7 +2116,7 @@  static void *get_any_partial(struct kmem
  * 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;
@@ -2124,11 +2124,11 @@  static void *get_partial(struct kmem_cac
 	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
@@ -2740,9 +2740,11 @@  new_slab:
 		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);
 
@@ -2766,7 +2768,6 @@  new_slab:
 	c->page = page;
 
 check_new_page:
-	page = c->page;
 	if (likely(!kmem_cache_debug(s) && pfmemalloc_match(page, gfpflags)))
 		goto load_freelist;