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memcg: bad page if page_cgroup when free

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Replace free_hot_cold_page's VM_BUG_ON(page_get_page_cgroup(page)) by a "Bad
page state" and clear: most users don't have CONFIG_DEBUG_VM on, and if it
were set here, it'd likely cause corruption when the page is reused.

Don't use page_assign_page_cgroup to clear it: that should be private to
memcontrol.c, and always called with the lock taken; and memmap_init_zone
doesn't need it either - like page->mapping and other pointers throughout the
kernel, Linux assumes pointers in zeroed structures are NULL pointers.

Instead use page_reset_bad_cgroup, added to memcontrol.h for this only.

Signed-off-by: Hugh Dickins <[email protected]>
Cc: David Rientjes <[email protected]>
Acked-by: Balbir Singh <[email protected]>
Acked-by: KAMEZAWA Hiroyuki <[email protected]>
Cc: Hirokazu Takahashi <[email protected]>
Cc: YAMAMOTO Takashi <[email protected]>
Cc: Paul Menage <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Hugh Dickins 2008-03-04 14:29:07 -08:00 • committed by Linus Torvalds
commit 9442ec9df4
3 changed files with 28 additions and 25 deletions
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27
mm/memcontrol.c
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@ -140,11 +140,17 @@ struct mem_cgroup {
/*
* We use the lower bit of the page->page_cgroup pointer as a bit spin
* lock. We need to ensure that page->page_cgroup is atleast two
* byte aligned (based on comments from Nick Piggin)
* lock. We need to ensure that page->page_cgroup is at least two
* byte aligned (based on comments from Nick Piggin). But since
* bit_spin_lock doesn't actually set that lock bit in a non-debug
* uniprocessor kernel, we should avoid setting it here too.
*/
#define PAGE_CGROUP_LOCK_BIT 0x0
#define PAGE_CGROUP_LOCK (1 << PAGE_CGROUP_LOCK_BIT)
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
#define PAGE_CGROUP_LOCK (1 << PAGE_CGROUP_LOCK_BIT)
#else
#define PAGE_CGROUP_LOCK 0x0
#endif
/*
* A page_cgroup page is associated with every page descriptor. The
@ -271,19 +277,10 @@ static inline int page_cgroup_locked(struct page *page)
&page->page_cgroup);
}
void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
static void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
{
int locked;
/*
* While resetting the page_cgroup we might not hold the
* page_cgroup lock. free_hot_cold_page() is an example
* of such a scenario
*/
if (pc)
VM_BUG_ON(!page_cgroup_locked(page));
locked = (page->page_cgroup & PAGE_CGROUP_LOCK);
page->page_cgroup = ((unsigned long)pc | locked);
VM_BUG_ON(!page_cgroup_locked(page));
page->page_cgroup = ((unsigned long)pc | PAGE_CGROUP_LOCK);
}
struct page_cgroup *page_get_page_cgroup(struct page *page)