Messages in this thread | | | Date | Wed, 21 Oct 2009 12:08:03 +0800 | Subject | Re: Question about invalidate_inode_pages2_range() | From | Peng Tao <> |
| |
On Tue, Oct 20, 2009 at 1:25 PM, Trond Myklebust <trond.myklebust@fys.uio.no> wrote: > On Mon, 2009-10-19 at 16:38 +0800, Peng Tao wrote: >> On Mon, Oct 19, 2009 at 4:26 PM, Trond Myklebust >> <trond.myklebust@fys.uio.no> wrote: >> > On Mon, 2009-10-19 at 16:16 +0800, Peng Tao wrote: >> >> Hi, >> >> >> >> I've a question about invalidate_inode_pages2_range(). >> >> >> >> When does invalidate_inode_pages2_range() returns -EBUSY? It locks and >> >> writes back the page. Why invalidate_complete_page2() still may fail >> >> due to page dirtiness? >> > >> > A lot of those requirements were set by NFS, which uses >> > invalidate_inode_pages2() in order to invalidate the page cache when it >> > detects that a file has been changed on the server (either due to an >> > O_DIRECT write, or due to another client modifying the file). >> > >> > In such cases, you want to try to keep the dirty data by writing it out >> > instead of discarding it. >> Thanks for your quick response. But I have two more questions about this. >> 1. invalidate_inode_pages2_range() calls wait_on_page_writeback(). >> Does the latter actually write out the dirty page? > > No. It just waits for any outstanding writeback activity on that page to > finish. Got it. Thank you. > >> 2. Is there any interface in the mm subsystem forces discarding a page cache? > > You mean that also discards dirty pages? Yes. That is what > truncate_inode_pages() does... But truncate_inode_pages() truncates all pages beyond lstart. Is there any way to discard a single page? truncate_inode_page() seems to be able to do the magic. But it is not exported.
> > >
-- Cheers, Peng Tao State Key Laboratory of Networking and Switching Technology Beijing Univ. of Posts and Telecoms.
| |