On Wed, 18 Jun 2008 10:13:49 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > On Tue, 17 Jun 2008 16:35:01 +0900 > Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx> > 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@xxxxxxxxxxxxxxxxx> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > --- > 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); > -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
