[PATCH v4 09/35] mm, slub: return slab page from get_partial() and set c->page afterwards

From: Vlastimil Babka
Date: Thu Aug 05 2021 - 11:23:23 EST


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@xxxxxxx>
---
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