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

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
...@@ -611,6 +611,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, ...@@ -611,6 +611,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
int rc = 0; int rc = 0;
int *result = NULL; int *result = NULL;
struct page *newpage = get_new_page(page, private, &result); struct page *newpage = get_new_page(page, private, &result);
int rcu_locked = 0;
if (!newpage) if (!newpage)
return -ENOMEM; return -ENOMEM;
...@@ -636,8 +637,13 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, ...@@ -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. * 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 * This rcu_read_lock() delays freeing anon_vma pointer until the end
* of migration. File cache pages are no problem because of page_lock() * 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. * This is a corner case handling.
* When a new swap-cache is read into, it is linked to LRU * 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, ...@@ -656,7 +662,8 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
if (rc) if (rc)
remove_migration_ptes(page, page); remove_migration_ptes(page, page);
rcu_unlock: rcu_unlock:
rcu_read_unlock(); if (rcu_locked)
rcu_read_unlock();
unlock: unlock:
......
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