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fix rcu_read_lock() in page migraton 

In migration fallback path, write_page() or lock_page() will be called.
This causes sleep with holding rcu_read_lock().
For avoding that, just do rcu_lock if the page is Anon.(this is enough.)

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki 2007-08-30 23:56:21 -07:00 committed by Linus Torvalds
parent d1254b12c9
commit 989f89c57e
1 changed files with 9 additions and 2 deletions
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11
mm/migrate.c
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@ -611,6 +611,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
int rc = 0;
int *result = NULL;
struct page *newpage = get_new_page(page, private, &result);
int rcu_locked = 0;
if (!newpage)
return -ENOMEM;
@ -636,8 +637,13 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
* we cannot notice that anon_vma is freed while we migrates a page.
* This rcu_read_lock() delays freeing anon_vma pointer until the end
* of migration. File cache pages are no problem because of page_lock()
* File Caches may use write_page() or lock_page() in migration, then,
* just care Anon page here.
*/
rcu_read_lock();
if (PageAnon(page)) {
rcu_read_lock();
rcu_locked = 1;
}
/*
* This is a corner case handling.
* When a new swap-cache is read into, it is linked to LRU
@ -656,7 +662,8 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
if (rc)
remove_migration_ptes(page, page);
rcu_unlock:
rcu_read_unlock();
if (rcu_locked)
rcu_read_unlock();
unlock: