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SubjectRe: sparc64 pgalloc.h pgd_quicklist question
On Fri, Jun 07, 2002 at 09:18:26AM +0100, Russell King wrote:
> On Thu, Jun 06, 2002 at 09:10:40PM -0500, Holzrichter, Bruce wrote:
> > I meant to ask this a little bit back, while I was looking through this
> > code. In the 2.5 iteration you have for small_page.c your using the
> > next_hash and pprev_hash entries, which no longer are available in the
> > struct page, as far as I have looked, unless your struct page is defined
> > elsewhere, other than linux/mm.h? Just wondering, as I pull apart the mm
> > code in what time I have looking at this.
>
> It looks like next_hash and pprev_hash migrated to list. (I've not
> confirmed that it obeys exactly the same rules yet.) The solution
> is probably to convert small-page.c to use the list stuff instead.
>
> If you don't get there before me, I'll probably fix it up this weekend.

Here's a patch that should be applied on top of the existing small_page.c
I've not tested it past the "does it compile" stage, so beware.

(Since mach-arc stuff is falling into disrepair, this code will probably
get removed from Linus' tree soon.)

--- orig/arch/arm/mach-arc/small_page.c Mon May 13 10:48:07 2002
+++ linux/arch/arm/mach-arc/small_page.c Sun Jun 9 23:32:42 2002
@@ -50,7 +50,7 @@
*/

struct order {
- struct page *queue;
+ struct list_head queue;
unsigned int mask; /* (1 << shift) - 1 */
unsigned int shift; /* (1 << shift) size of page */
unsigned int block_mask; /* nr_blocks - 1 */
@@ -60,10 +60,10 @@

static struct order orders[] = {
#if PAGE_SIZE == 4096
- { NULL, 2047, 11, 1, 0x00000003 }
+ { LIST_HEAD_INIT(orders[0].queue), 2047, 11, 1, 0x00000003 }
#elif PAGE_SIZE == 32768
- { NULL, 2047, 11, 15, 0x0000ffff },
- { NULL, 8191, 13, 3, 0x0000000f }
+ { LIST_HEAD_INIT(orders[0].queue), 2047, 11, 15, 0x0000ffff },
+ { LIST_HEAD_INIT(orders[1].queue), 8191, 13, 3, 0x0000000f }
#else
#error unsupported page size
#endif
@@ -75,70 +75,49 @@

static spinlock_t small_page_lock = SPIN_LOCK_UNLOCKED;

-static void add_page_to_queue(struct page *page, struct page **p)
-{
-#ifdef PEDANTIC
- if (page->pprev_hash)
- PAGE_BUG(page);
-#endif
- page->next_hash = *p;
- if (*p)
- (*p)->pprev_hash = &page->next_hash;
- *p = page;
- page->pprev_hash = p;
-}
-
-static void remove_page_from_queue(struct page *page)
-{
- if (page->pprev_hash) {
- if (page->next_hash)
- page->next_hash->pprev_hash = page->pprev_hash;
- *page->pprev_hash = page->next_hash;
- page->pprev_hash = NULL;
- }
-}
-
static unsigned long __get_small_page(int priority, struct order *order)
{
unsigned long flags;
struct page *page;
int offset;

- if (!order->queue)
- goto need_new_page;
+ do {
+ spin_lock_irqsave(&small_page_lock, flags);
+
+ if (list_empty(&order->queue))
+ goto need_new_page;

- spin_lock_irqsave(&small_page_lock, flags);
- page = order->queue;
+ page = list_entry(order->queue.next, struct page, list);
again:
#ifdef PEDANTIC
- if (USED_MAP(page) & ~order->all_used)
- PAGE_BUG(page);
+ if (USED_MAP(page) & ~order->all_used)
+ PAGE_BUG(page);
#endif
- offset = ffz(USED_MAP(page));
- SET_USED(page, offset);
- if (USED_MAP(page) == order->all_used)
- remove_page_from_queue(page);
- spin_unlock_irqrestore(&small_page_lock, flags);
+ offset = ffz(USED_MAP(page));
+ SET_USED(page, offset);
+ if (USED_MAP(page) == order->all_used)
+ list_del_init(&page->list);
+ spin_unlock_irqrestore(&small_page_lock, flags);

- return (unsigned long) page_address(page) + (offset << order->shift);
+ return (unsigned long) page_address(page) + (offset << order->shift);

need_new_page:
- page = alloc_page(priority);
+ spin_unlock_irqrestore(&small_page_lock, flags);
+ page = alloc_page(priority);
+ spin_lock_irqsave(&small_page_lock, flags);
+
+ if (list_empty(&order->queue)) {
+ if (!page)
+ goto no_page;
+ SetPageReserved(page);
+ USED_MAP(page) = 0;
+ list_add(&page->list, &order->queue);
+ goto again;
+ }

- spin_lock_irqsave(&small_page_lock, flags);
- if (!order->queue) {
- if (!page)
- goto no_page;
- SetPageReserved(page);
- USED_MAP(page) = 0;
- cli();
- add_page_to_queue(page, &order->queue);
- } else {
+ spin_unlock_irqrestore(&small_page_lock, flags);
__free_page(page);
- cli();
- page = order->queue;
- }
- goto again;
+ } while (1);

no_page:
spin_unlock_irqrestore(&small_page_lock, flags);
@@ -173,7 +152,7 @@
spin_lock_irqsave(&small_page_lock, flags);

if (USED_MAP(page) == order->all_used)
- add_page_to_queue(page, &order->queue);
+ list_add(&page->list, &order->queue);

if (!TEST_AND_CLEAR_USED(page, spage))
goto already_free;
@@ -189,7 +168,7 @@
/*
* unlink the page from the small page queue and free it
*/
- remove_page_from_queue(page);
+ list_del_init(&page->list);
spin_unlock_irqrestore(&small_page_lock, flags);
ClearPageReserved(page);
__free_page(page);
--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html

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