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@suse.cz>

diff --git a/mm/slub.c b/mm/slub.c
index 0c645b0..e9d582e 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2017,7 +2017,7 @@ 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;
@@ -2046,7 +2046,7 @@ 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 {
@@ -2066,7 +2066,7 @@ 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;
@@ -2108,7 +2108,7 @@ 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()
@@ -2130,7 +2130,7 @@ 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;
@@ -2138,11 +2138,11 @@ 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
@@ -2754,9 +2754,11 @@ 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);
 
@@ -2780,7 +2782,6 @@ new_slab:
        c->page = page;
 
 check_new_page:
-       page = c->page;
        if (likely(!kmem_cache_debug(s) && pfmemalloc_match(page, gfpflags)))
                goto load_freelist;