[patch 2/6] SLUB: Do not use page->mapping

From: Christoph Lameter
Date: Thu Aug 23 2007 - 02:48:29 EST


After moving the lockless_freelist to kmem_cache_cpu we no longer need
page->lockless_freelist. Restructure the use of the struct page fields in
such a way that we never touch the mapping field.

This is turn allows us to remove the special casing of SLUB when determining
the mapping of a page (needed for corner cases of virtual caches machines that
need to flush caches of processors mapping a page).

Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
---
include/linux/mm_types.h | 9 ++-------
mm/slub.c | 2 --
2 files changed, 2 insertions(+), 9 deletions(-)

Index: linux-2.6.23-rc3-mm1/include/linux/mm_types.h
===================================================================
--- linux-2.6.23-rc3-mm1.orig/include/linux/mm_types.h 2007-08-22 17:14:32.000000000 -0700
+++ linux-2.6.23-rc3-mm1/include/linux/mm_types.h 2007-08-22 17:20:13.000000000 -0700
@@ -62,13 +62,8 @@ struct page {
#if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
spinlock_t ptl;
#endif
- struct { /* SLUB uses */
- void **lockless_freelist;
- struct kmem_cache *slab; /* Pointer to slab */
- };
- struct {
- struct page *first_page; /* Compound pages */
- };
+ struct kmem_cache *slab; /* SLUB: Pointer to slab */
+ struct page *first_page; /* Compound tail pages */
};
union {
pgoff_t index; /* Our offset within mapping. */
Index: linux-2.6.23-rc3-mm1/mm/slub.c
===================================================================
--- linux-2.6.23-rc3-mm1.orig/mm/slub.c 2007-08-22 17:20:05.000000000 -0700
+++ linux-2.6.23-rc3-mm1/mm/slub.c 2007-08-22 17:20:13.000000000 -0700
@@ -1125,7 +1125,6 @@ static struct page *new_slab(struct kmem
set_freepointer(s, last, NULL);

page->freelist = start;
- page->lockless_freelist = NULL;
page->inuse = 0;
out:
if (flags & __GFP_WAIT)
@@ -1151,7 +1150,6 @@ static void __free_slab(struct kmem_cach
NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
- pages);

- page->mapping = NULL;
__free_pages(page, s->order);
}


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