On Mon, 2007-10-29 at 19:17 +0100, Peter Zijlstra wrote: > On Mon, 2007-10-29 at 13:51 -0400, Jaya Kumar wrote: > > On 10/29/07, Peter Zijlstra <[EMAIL PROTECTED]> wrote: > > > On Mon, 2007-10-29 at 01:17 -0700, Jaya Kumar wrote: > > > > 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. > > > > > > OK, seems I can't read. Or at least, I missed a large part of the > > > problem. > > > > > > page_mkclean() hasn't changed, it was ->page_mkwrite() that changed. And > > > looking at the fb_defio code, I'm not sure I understand how its > > > page_mkclean() use could ever have worked. > > > > > > The proposed patch [1] only fixes the issue of ->page_mkwrite() on > > > vmalloc()'ed memory. Not page_mkclean(), and that has never worked from > > > what I can make of it. > > > > > > Jaya, could you shed some light on this? I presume you had your display > > > working. > > > > > > > I thought I had it working. I saw the display update after each > > mmap/write sequence to the framebuffer. I need to check if there's an > > munmap or anything else going on in between write sequences that would > > cause it to behave like page_mkclean was working. > > > > Is it correct to assume that page_mkclean should mark the pages > > read-only so that the next write would again trigger mkwrite? > > Well, yes, that is the intended behaviour. > > > Even if the page was from a vmalloc_to_page()? > > That is the crux, I only ever implemented it for file pages.
Hmm, so these vmalloc pages are mapped into user-space with remap_pfn_range(), which doesn't have any form of rmap. That is, given a pfn there is no way to obtain all ptes for it. So the interface to page_mkclean() could never work for these (as it only provides a struct page *). [ also, remap_vmalloc_range() suffers similar issues, only file and anon have proper rmap ] I'm not sure we want full rmap for remap_pfn/vmalloc_range, but perhaps we could assist drivers in maintaining and using vma lists. I think page_mkclean_one() would work if you'd manually set page->index and iterate the vmas yourself. Although atm I'm not sure of anything so don't pin me on it. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
