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[PATCH] mm: migration page refcounting fix

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Migration code currently does not take a reference to target page
properly, so between unlocking the pte and trying to take a new
reference to the page with isolate_lru_page, anything could happen to
it.

Fix this by holding the pte lock until we get a chance to elevate the
refcount.

Other small cleanups while we're here.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin
2006-01-18 17:42:27 -08:00
committed by Linus Torvalds
parent e236a166b2
commit 053837fce7
7 changed files with 76 additions and 75 deletions
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71
mm/vmscan.c
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@@ -586,7 +586,7 @@ static inline void move_to_lru(struct page *page)
}
/*
* Add isolated pages on the list back to the LRU
* Add isolated pages on the list back to the LRU.
*
* returns the number of pages put back.
*/
@@ -760,46 +760,33 @@ next:
return nr_failed + retry;
}
static void lru_add_drain_per_cpu(void *dummy)
{
lru_add_drain();
}
/*
* Isolate one page from the LRU lists and put it on the
* indicated list. Do necessary cache draining if the
* page is not on the LRU lists yet.
* indicated list with elevated refcount.
*
* Result:
* 0 = page not on LRU list
* 1 = page removed from LRU list and added to the specified list.
* -ENOENT = page is being freed elsewhere.
*/
int isolate_lru_page(struct page *page)
{
int rc = 0;
struct zone *zone = page_zone(page);
int ret = 0;
redo:
spin_lock_irq(&zone->lru_lock);
rc = __isolate_lru_page(page);
if (rc == 1) {
if (PageActive(page))
del_page_from_active_list(zone, page);
else
del_page_from_inactive_list(zone, page);
if (PageLRU(page)) {
struct zone *zone = page_zone(page);
spin_lock_irq(&zone->lru_lock);
if (TestClearPageLRU(page)) {
ret = 1;
get_page(page);
if (PageActive(page))
del_page_from_active_list(zone, page);
else
del_page_from_inactive_list(zone, page);
}
spin_unlock_irq(&zone->lru_lock);
}
spin_unlock_irq(&zone->lru_lock);
if (rc == 0) {
/*
* Maybe this page is still waiting for a cpu to drain it
* from one of the lru lists?
*/
rc = schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
if (rc == 0 && PageLRU(page))
goto redo;
}
return rc;
return ret;
}
#endif
@@ -831,18 +818,20 @@ static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
page = lru_to_page(src);
prefetchw_prev_lru_page(page, src, flags);
switch (__isolate_lru_page(page)) {
case 1:
/* Succeeded to isolate page */
list_move(&page->lru, dst);
nr_taken++;
break;
case -ENOENT:
/* Not possible to isolate */
list_move(&page->lru, src);
break;
default:
if (!TestClearPageLRU(page))
BUG();
list_del(&page->lru);
if (get_page_testone(page)) {
/*
* It is being freed elsewhere
*/
__put_page(page);
SetPageLRU(page);
list_add(&page->lru, src);
continue;
} else {
list_add(&page->lru, dst);
nr_taken++;
}
}