lkml.org 
[lkml]   [2008]   [Jun]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH][RFC] fix kernel BUG at mm/migrate.c:719! in 2.6.26-rc5-mm3
On Wed, 18 Jun 2008 10:13:49 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Tue, 17 Jun 2008 16:35:01 +0900
> Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
>
> > This patch also fixes a race between migrate_entry_wait and
> > page_freeze_refs in migrate_page_move_mapping.
> >
> Ok, let's fix one by one. please add your Signed-off-by if ok.
>
Agree. It should be fixed independently.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

> This is a fix for page migration under speculative page lookup protocol.
> -Kame
> ==
> In speculative page cache lookup protocol, page_count(page) is set to 0
> while radix-tree midification is going on, truncation, migration, etc...
>
> While page migration, a page fault to page under migration should wait
> unlock_page() and migration_entry_wait() waits for the page from its
> pte entry. It does get_page() -> wait_on_page_locked() -> put_page() now.
>
> In page migration, page_freeze_refs() -> page_unfreeze_refs() is called.
>
> Here, page_unfreeze_refs() expects page_count(page) == 0 and panics
> if page_count(page) != 0. To avoid this, we shouldn't touch page_count()
> if it is zero. This patch uses page_cache_get_speculative() to avoid
> the panic.
>
> From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
> mm/migrate.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> Index: test-2.6.26-rc5-mm3/mm/migrate.c
> ===================================================================
> --- test-2.6.26-rc5-mm3.orig/mm/migrate.c
> +++ test-2.6.26-rc5-mm3/mm/migrate.c
> @@ -243,7 +243,8 @@ void migration_entry_wait(struct mm_stru
>
> page = migration_entry_to_page(entry);
>
> - get_page(page);
> + if (!page_cache_get_speculative())
> + goto out;
> pte_unmap_unlock(ptep, ptl);
> wait_on_page_locked(page);
> put_page(page);
>



\
 
 \ /
  Last update: 2008-06-18 03:29    [from the cache]
©2003-2011 Jasper Spaans