mm: slab/slub: use page->list consistently instead of page->lru

'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@linux.intel.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

3 files changed, 9 insertions, 8 deletions

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 290901a8c1de..84b74080beb7 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -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 --git a/mm/slab.c b/mm/slab.c
index 8dd8e0875e4c..f6718197cdd0 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2922,9 +2922,9 @@ 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 --git a/mm/slob.c b/mm/slob.c
index 4bf8809dfcce..730cad45d4be 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -111,13 +111,13 @@ static inline int slob_page_free(struct page *sp)
 
 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_t gfp, int align, int node)
 
         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_t gfp, int align, int node)
                         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_t gfp, int align, int node)
                 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);