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Commit 989f89c5 authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
Browse files

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: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d1254b12

mm/migrate.c

+9 −2
Original line number Diff line number Diff line
@@ -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.

	 */

	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
@@ -656,6 +662,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 
	if (rc)

		remove_migration_ptes(page, page);

rcu_unlock:

	if (rcu_locked)

		rcu_read_unlock();



unlock: