On Mon, 2006-06-19 at 17:07 -0700, Andrew Morton wrote: > Mark Fasheh <mark.fasheh@xxxxxxxxxx> wrote: > > > > I finally got some time to sit down and implement an OCFS2 patch to make use > > of the ->page_mkwrite() callback added by David Howells' patch (named > > 'add-page_mkwrite-vm_operations-method.patch' in -mm). The patches, and an > > MPI program to test this can be found at: > > > > http://kernel.org/pub/linux/kernel/people/mfasheh/ocfs2/mmap/ > > > > There's one bug however, which will cause the test program on one of the > > reading nodes to see stale data if it is run several times in a row against > > the same file. I have verified that the same thing works fine on a local > > file system (ext3). I'm not sure where the issue is, but I have a feeling > > I'm doing something bad in ocfs2_data_convert_worker(). Another possibility > > is that we missed a place to put the ->page_mkwrite callback. > > > > Unfortunately, I have to step away from this patch for a bit as I have some > > higher priority issues to deal with :/ Luckily, it seems to be in a state > > which I think warrants it being pushed out to the public for general review, > > testing, etc. If anyone is interested, I'd also appreciate any advice or > > help regarding the bug -- my VM-foo is very weak :) > > Peter Zijlstra told me yesterday: > > There is a problem with the page-mkwrite last posted to lkml. /me > checks your tree... Yeah, that version has a problem: > http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.17-rc6/2.6.17-rc6-mm2/broken-out/add-page_mkwrite-vm_operations-method.patch > > The thing is that get_user_pages(.write=1, .force=1) can generate COW > hits on read-only shared mappings, this patch traps those as mkpage_write > candidates and fails to handle them the old way. The -v9 version of the dirty page tracking I send out fixes this problem by affiliation; the following patch should also be enough: --- mm/memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) Index: 2.6-mm/mm/memory.c =================================================================== --- 2.6-mm.orig/mm/memory.c 2006-06-20 09:02:58.000000000 +0200 +++ 2.6-mm/mm/memory.c 2006-06-20 09:06:01.000000000 +0200 @@ -1464,7 +1464,8 @@ static int do_wp_page(struct mm_struct * if (!old_page) goto gotten; - if (unlikely(vma->vm_flags & VM_SHARED)) { + if (unlikely(vma->vm_flags & (VM_SHARED|VM_WRITE) == + VM_SHARED|VM_WRITE) { if (vma->vm_ops && vma->vm_ops->page_mkwrite) { /* * Notify the address space that the page is about to - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
