From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
'struct page' has two list_head fields: 'lru' and 'list'.
Conveniently, they are unioned together. This means that code
can use them interchangably, which gets horribly confusing like
with this nugget from slab.c:
> list_del(&page->lru);
> if (page->active == cachep->num)
> list_add(&page->list, &n->slabs_full);
This patch makes the slab and slub code use page->lru
universally instead of mixing ->list and ->lru.
So, the new rule is: page->lru is what the you use if you want to
keep your page on a list. Don't like the fact that it's not
called ->list? Too bad.
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
---
b/include/linux/mm_types.h | 3 ++-
b/mm/slab.c | 4 ++--
b/mm/slob.c | 10 +++++-----
3 files changed, 9 insertions(+), 8 deletions(-)
diff -puN include/linux/mm_types.h~make-slab-use-page-lru-vs-list-consistently include/linux/mm_types.h
--- a/include/linux/mm_types.h~make-slab-use-page-lru-vs-list-consistently 2014-01-14 09:57:56.099621967 -0800
+++ b/include/linux/mm_types.h 2014-01-14 09:57:56.106622281 -0800
@@ -124,6 +124,8 @@ struct page {
union {
struct list_head lru; /* Pageout list, eg. active_list
* protected by zone->lru_lock !
+ * Can be used as a generic list
+ * by the page owner.
*/
struct { /* slub per cpu partial pages */
struct page *next; /* Next partial slab */
@@ -136,7 +138,6 @@ struct page {
#endif
};
- struct list_head list; /* slobs list of pages */
struct slab *slab_page; /* slab fields */
struct rcu_head rcu_head; /* Used by SLAB
* when destroying via RCU
diff -puN mm/slab.c~make-slab-use-page-lru-vs-list-consistently mm/slab.c
--- a/mm/slab.c~make-slab-use-page-lru-vs-list-consistently 2014-01-14 09:57:56.101622056 -0800
+++ b/mm/slab.c 2014-01-14 09:57:56.108622370 -0800
@@ -2886,9 +2886,9 @@ retry:
/* move slabp to correct slabp list: */
list_del(&page->lru);
if (page->active == cachep->num)
- list_add(&page->list, &n->slabs_full);
+ list_add(&page->lru, &n->slabs_full);
else
- list_add(&page->list, &n->slabs_partial);
+ list_add(&page->lru, &n->slabs_partial);
}
must_grow:
diff -puN mm/slob.c~make-slab-use-page-lru-vs-list-consistently mm/slob.c
--- a/mm/slob.c~make-slab-use-page-lru-vs-list-consistently 2014-01-14 09:57:56.103622146 -0800
+++ b/mm/slob.c 2014-01-14 09:57:56.109622415 -0800
@@ -111,13 +111,13 @@ static inline int slob_page_free(struct
static void set_slob_page_free(struct page *sp, struct list_head *list)
{
- list_add(&sp->list, list);
+ list_add(&sp->lru, list);
__SetPageSlobFree(sp);
}
static inline void clear_slob_page_free(struct page *sp)
{
- list_del(&sp->list);
+ list_del(&sp->lru);
__ClearPageSlobFree(sp);
}
@@ -282,7 +282,7 @@ static void *slob_alloc(size_t size, gfp
spin_lock_irqsave(&slob_lock, flags);
/* Iterate through each partially free page, try to find room */
- list_for_each_entry(sp, slob_list, list) {
+ list_for_each_entry(sp, slob_list, lru) {
#ifdef CONFIG_NUMA
/*
* If there's a node specification, search for a partial
@@ -296,7 +296,7 @@ static void *slob_alloc(size_t size, gfp
continue;
/* Attempt to alloc */
- prev = sp->list.prev;
+ prev = sp->lru.prev;
b = slob_page_alloc(sp, size, align);
if (!b)
continue;
@@ -322,7 +322,7 @@ static void *slob_alloc(size_t size, gfp
spin_lock_irqsave(&slob_lock, flags);
sp->units = SLOB_UNITS(PAGE_SIZE);
sp->freelist = b;
- INIT_LIST_HEAD(&sp->list);
+ INIT_LIST_HEAD(&sp->lru);
set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
set_slob_page_free(sp, slob_list);
b = slob_page_alloc(sp, size, align);
_
--
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