From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: vm_ops.page_mkwrite() fails with vmalloc on 2.6.23 From: Peter Zijlstra In-Reply-To: <1193652717.27652.45.camel@twins> References: <1193064057.16541.1.camel@matrix> <20071029004002.60c7182a.akpm@linux-foundation.org> <45a44e480710290117u492dbe82ra6344baf8bb1e370@mail.gmail.com> <1193652717.27652.45.camel@twins> Content-Type: text/plain Date: Mon, 29 Oct 2007 13:35:08 +0100 Message-Id: <1193661308.27652.47.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Jaya Kumar Cc: Andrew Morton , stefani@seibold.net, linux-kernel@vger.kernel.org, David Howells , linux-mm@kvack.org, Nick Piggin List-ID: On Mon, 2007-10-29 at 11:11 +0100, Peter Zijlstra wrote: > On Mon, 2007-10-29 at 01:17 -0700, Jaya Kumar wrote: > > On 10/29/07, Andrew Morton wrote: > > > On Mon, 22 Oct 2007 16:40:57 +0200 Stefani Seibold wrote: > > > > > > > > The problem original occurs with the fb_defio driver (driver/video/fb_defio.c). > > > > This driver use the vm_ops.page_mkwrite() handler for tracking the modified pages, > > > > which will be in an extra thread handled, to perform the IO and clean and > > > > write protect all pages with page_clean(). > > > > > > > > Hi, > > > > An aside, I just tested that deferred IO works fine on 2.6.22.10/pxa255. > > > > I understood from the thread that PeterZ is looking into page_mkclean > > changes which I guess went into 2.6.23. I'm also happy to help in any > > way if the way we're doing fb_defio needs to change. > > Yeah, its the truncate race stuff introduced by Nick in > d0217ac04ca6591841e5665f518e38064f4e65bd > > I'm a bit at a loss on how to go around fixing this. One ugly idea I had > was to check page->mapping before going into page_mkwrite() and when > that is null, don't bother with the truncate check. Something like this --- mm/memory.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) Index: linux-2.6/mm/memory.c =================================================================== --- linux-2.6.orig/mm/memory.c +++ linux-2.6/mm/memory.c @@ -2300,6 +2300,8 @@ static int __do_fault(struct mm_struct * * to become writable */ if (vma->vm_ops->page_mkwrite) { + struct address_space *mapping = page->mapping; + unlock_page(page); if (vma->vm_ops->page_mkwrite(vma, page) < 0) { ret = VM_FAULT_SIGBUS; @@ -2314,7 +2316,7 @@ static int __do_fault(struct mm_struct * * reworking page_mkwrite locking API, which * is better done later. */ - if (!page->mapping) { + if (mapping != page->mapping) { ret = 0; anon = 1; /* no anon but release vmf.page */ goto out; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org