From: Dave Hansen <dave.han...@linux.intel.com>
'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->list
universally instead of mixing ->list and ->lru.
It also adds some comments to attempt to keep new users from
picking up uses of ->list.
So, the new rule is: page->list is what the slabs use. page->lru
is for everybody else. This is a pretty arbitrary rule, but we
need _something_. Maybe we should just axe the ->list one and
make the sl?bs use ->lru.
Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
---
linux.git-davehans/include/linux/mm_types.h | 5 ++
linux.git-davehans/mm/slab.c | 50 ++++++++++++++--------------
2 files changed, 29 insertions(+), 26 deletions(-)
diff -puN include/linux/mm_types.h~make-slab-use-page-lru-vs-list-consistently
include/linux/mm_types.h
---
linux.git/include/linux/mm_types.h~make-slab-use-page-lru-vs-list-consistently
2013-12-11 14:34:51.438183588 -0800
+++ linux.git-davehans/include/linux/mm_types.h 2013-12-11 14:34:51.445183899
-0800
@@ -123,6 +123,8 @@ 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 */
@@ -135,7 +137,8 @@ struct page {
#endif
};
- struct list_head list; /* slobs list of pages */
+ struct list_head list; /* sl[aou]bs list of pages.
+ * do not use outside of slabs */
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
--- linux.git/mm/slab.c~make-slab-use-page-lru-vs-list-consistently
2013-12-11 14:34:51.440183677 -0800
+++ linux.git-davehans/mm/slab.c 2013-12-11 14:34:51.444183855 -0800
@@ -765,15 +765,15 @@ static void recheck_pfmemalloc_active(st
return;
spin_lock_irqsave(&n->list_lock, flags);
- list_for_each_entry(page, &n->slabs_full, lru)
+ list_for_each_entry(page, &n->slabs_full, list)
if (is_slab_pfmemalloc(page))
goto out;
- list_for_each_entry(page, &n->slabs_partial, lru)
+ list_for_each_entry(page, &n->slabs_partial, list)
if (is_slab_pfmemalloc(page))
goto out;
- list_for_each_entry(page, &n->slabs_free, lru)
+ list_for_each_entry(page, &n->slabs_free, list)
if (is_slab_pfmemalloc(page))
goto out;
@@ -1428,7 +1428,7 @@ void __init kmem_cache_init(void)
{
int i;
- BUILD_BUG_ON(sizeof(((struct page *)NULL)->lru) <
+ BUILD_BUG_ON(sizeof(((struct page *)NULL)->list) <
sizeof(struct rcu_head));
kmem_cache = &kmem_cache_boot;
setup_node_pointer(kmem_cache);
@@ -1624,15 +1624,15 @@ slab_out_of_memory(struct kmem_cache *ca
continue;
spin_lock_irqsave(&n->list_lock, flags);
- list_for_each_entry(page, &n->slabs_full, lru) {
+ list_for_each_entry(page, &n->slabs_full, list) {
active_objs += cachep->num;
active_slabs++;
}
- list_for_each_entry(page, &n->slabs_partial, lru) {
+ list_for_each_entry(page, &n->slabs_partial, list) {
active_objs += page->active;
active_slabs++;
}
- list_for_each_entry(page, &n->slabs_free, lru)
+ list_for_each_entry(page, &n->slabs_free, list)
num_slabs++;
free_objects += n->free_objects;
@@ -2424,11 +2424,11 @@ static int drain_freelist(struct kmem_ca
goto out;
}
- page = list_entry(p, struct page, lru);
+ page = list_entry(p, struct page, list);
#if DEBUG
BUG_ON(page->active);
#endif
- list_del(&page->lru);
+ list_del(&page->list);
/*
* Safe to drop the lock. The slab is no longer linked
* to the cache.
@@ -2721,7 +2721,7 @@ static int cache_grow(struct kmem_cache
spin_lock(&n->list_lock);
/* Make slab active. */
- list_add_tail(&page->lru, &(n->slabs_free));
+ list_add_tail(&page->list, &(n->slabs_free));
STATS_INC_GROWN(cachep);
n->free_objects += cachep->num;
spin_unlock(&n->list_lock);
@@ -2864,7 +2864,7 @@ retry:
goto must_grow;
}
- page = list_entry(entry, struct page, lru);
+ page = list_entry(entry, struct page, list);
check_spinlock_acquired(cachep);
/*
@@ -2884,7 +2884,7 @@ retry:
}
/* move slabp to correct slabp list: */
- list_del(&page->lru);
+ list_del(&page->list);
if (page->active == cachep->num)
list_add(&page->list, &n->slabs_full);
else
@@ -3163,7 +3163,7 @@ retry:
goto must_grow;
}
- page = list_entry(entry, struct page, lru);
+ page = list_entry(entry, struct page, list);
check_spinlock_acquired_node(cachep, nodeid);
STATS_INC_NODEALLOCS(cachep);
@@ -3175,12 +3175,12 @@ retry:
obj = slab_get_obj(cachep, page, nodeid);
n->free_objects--;
/* move slabp to correct slabp list: */
- list_del(&page->lru);
+ list_del(&page->list);
if (page->active == cachep->num)
- list_add(&page->lru, &n->slabs_full);
+ list_add(&page->list, &n->slabs_full);
else
- list_add(&page->lru, &n->slabs_partial);
+ list_add(&page->list, &n->slabs_partial);
spin_unlock(&n->list_lock);
goto done;
@@ -3337,7 +3337,7 @@ static void free_block(struct kmem_cache
page = virt_to_head_page(objp);
n = cachep->node[node];
- list_del(&page->lru);
+ list_del(&page->list);
check_spinlock_acquired_node(cachep, node);
slab_put_obj(cachep, page, objp, node);
STATS_DEC_ACTIVE(cachep);
@@ -3355,14 +3355,14 @@ static void free_block(struct kmem_cache
*/
slab_destroy(cachep, page);
} else {
- list_add(&page->lru, &n->slabs_free);
+ list_add(&page->list, &n->slabs_free);
}
} else {
/* Unconditionally move a slab to the end of the
* partial list on free - maximum time for the
* other objects to be freed, too.
*/
- list_add_tail(&page->lru, &n->slabs_partial);
+ list_add_tail(&page->list, &n->slabs_partial);
}
}
}
@@ -3404,7 +3404,7 @@ free_done:
while (p != &(n->slabs_free)) {
struct page *page;
- page = list_entry(p, struct page, lru);
+ page = list_entry(p, struct page, list);
BUG_ON(page->active);
i++;
@@ -4029,13 +4029,13 @@ void get_slabinfo(struct kmem_cache *cac
check_irq_on();
spin_lock_irq(&n->list_lock);
- list_for_each_entry(page, &n->slabs_full, lru) {
+ list_for_each_entry(page, &n->slabs_full, list) {
if (page->active != cachep->num && !error)
error = "slabs_full accounting error";
active_objs += cachep->num;
active_slabs++;
}
- list_for_each_entry(page, &n->slabs_partial, lru) {
+ list_for_each_entry(page, &n->slabs_partial, list) {
if (page->active == cachep->num && !error)
error = "slabs_partial accounting error";
if (!page->active && !error)
@@ -4043,7 +4043,7 @@ void get_slabinfo(struct kmem_cache *cac
active_objs += page->active;
active_slabs++;
}
- list_for_each_entry(page, &n->slabs_free, lru) {
+ list_for_each_entry(page, &n->slabs_free, list) {
if (page->active && !error)
error = "slabs_free accounting error";
num_slabs++;
@@ -4266,9 +4266,9 @@ static int leaks_show(struct seq_file *m
check_irq_on();
spin_lock_irq(&n->list_lock);
- list_for_each_entry(page, &n->slabs_full, lru)
+ list_for_each_entry(page, &n->slabs_full, list)
handle_slab(x, cachep, page);
- list_for_each_entry(page, &n->slabs_partial, lru)
+ list_for_each_entry(page, &n->slabs_partial, list)
handle_slab(x, cachep, page);
spin_unlock_irq(&n->list_lock);
}
_
--
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