Re: [PATCH] anobjrmap 1/6 objrmap

[William Lee Irwin III <wli@holomorphy.com>]

On Wed, Mar 24, 2004 at 12:01:56PM -0800, William Lee Irwin III wrote:
> Don't confuse unslabify and the ->list removal. The ->list removal went
> around insisting the known universe stop using ->lru because of the
> relatively arbitrary choice that slab.c use ->lru. The unslabify patch
> attempts to update one user of ->lru by backing out the code using it.
> Do note that non-list-heads like ->index, ->private, or ->mapping are
> also unused on slab pages, and could have saved some pain for this
> former user of ->list had they been chosen.

Updating the user instead of backing them out would have looked
something like the following (totally untested, not even compiletested):


-- wli


Index: mm2-2.6.5-rc2-1/arch/i386/mm/pageattr.c
===================================================================
--- mm2-2.6.5-rc2-1.orig/arch/i386/mm/pageattr.c	2004-03-19 16:11:06.000000000 -0800
+++ mm2-2.6.5-rc2-1/arch/i386/mm/pageattr.c	2004-03-21 07:15:40.000000000 -0800
@@ -75,7 +75,7 @@
 		return;
 
 	spin_lock_irqsave(&pgd_lock, flags);
-	list_for_each_entry(page, &pgd_list, lru) {
+	for (page = pgd_list; page; page = (struct page *)page->index) {
 		pgd_t *pgd;
 		pmd_t *pmd;
 		pgd = (pgd_t *)page_address(page) + pgd_index(address);
Index: mm2-2.6.5-rc2-1/arch/i386/mm/pgtable.c
===================================================================
--- mm2-2.6.5-rc2-1.orig/arch/i386/mm/pgtable.c	2004-03-21 07:14:22.000000000 -0800
+++ mm2-2.6.5-rc2-1/arch/i386/mm/pgtable.c	2004-03-21 07:18:41.000000000 -0800
@@ -172,7 +172,27 @@
  * -- wli
  */
 spinlock_t pgd_lock = SPIN_LOCK_UNLOCKED;
-LIST_HEAD(pgd_list);
+struct page *pgd_list;
+
+static inline void pgd_list_add(pgd_t *pgd)
+{
+	struct page *page = virt_to_page(pgd);
+	page->index = (unsigned long)pgd_list;
+	if (pgd_list)
+		pgd_list->private = (unsigned long)&page->index;
+	pgd_list = page;
+	page->private = (unsigned long)&pgd_list;
+}
+
+static inline void pgd_list_del(pgd_t *pgd)
+{
+	struct page *next, **pprev, *page = virt_to_page(pgd);
+	next = (struct page *)page->index;
+	pprev = (struct page **)page->private;
+	*pprev = next;
+	if (next)
+		next->private = (unsigned long)pprev;
+}
 
 void pgd_ctor(void *pgd, kmem_cache_t *cache, unsigned long unused)
 {
@@ -188,7 +208,7 @@
 	if (PTRS_PER_PMD > 1)
 		return;
 
-	list_add(&virt_to_page(pgd)->lru, &pgd_list);
+	pgd_list_add(pgd);
 	spin_unlock_irqrestore(&pgd_lock, flags);
 	memset(pgd, 0, USER_PTRS_PER_PGD*sizeof(pgd_t));
 }
@@ -199,7 +219,7 @@
 	unsigned long flags; /* can be called from interrupt context */
 
 	spin_lock_irqsave(&pgd_lock, flags);
-	list_del(&virt_to_page(pgd)->lru);
+	pgd_list_del(pgd);
 	spin_unlock_irqrestore(&pgd_lock, flags);
 }
 
Index: mm2-2.6.5-rc2-1/include/asm-i386/pgtable.h
===================================================================
--- mm2-2.6.5-rc2-1.orig/include/asm-i386/pgtable.h	2004-03-19 16:11:34.000000000 -0800
+++ mm2-2.6.5-rc2-1/include/asm-i386/pgtable.h	2004-03-21 08:27:30.000000000 -0800
@@ -35,7 +35,7 @@
 extern kmem_cache_t *pgd_cache;
 extern kmem_cache_t *pmd_cache;
 extern spinlock_t pgd_lock;
-extern struct list_head pgd_list;
+extern struct page *pgd_list;
 
 void pmd_ctor(void *, kmem_cache_t *, unsigned long);
 void pgd_ctor(void *, kmem_cache_t *, unsigned long);