> In speculative page cache look up protocol, page_count(page) is set to 0 > while radix-tree modification is going on, truncation, migration, etc... > > While page migration, a page fault to page under migration does > - look up page table > - find it is migration_entry_pte > - decode pfn from migration_entry_pte and get page of pfn_page(pfn) > - wait until page is unlocked > > It does get_page() -> wait_on_page_locked() -> put_page() now. > > In page migration's radix-tree replacement, page_freeze_refs() -> > page_unfreeze_refs() is called. And page_count(page) turns to be zero > and must be kept to be zero while radix-tree replacement. > > If get_page() is called against a page under radix-tree replacement, > the kernel panics(). To avoid this, we shouldn't increment page_count() > if it is zero. This patch uses get_page_unless_zero(). > > Even if get_page_unless_zero() fails, the caller just retries. > But will be a bit busier. Great! Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> -- 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
