Thanks you for sending. I'll perform testing and share results next. On 3/17/23 12:20 AM, Peter Xu wrote: > Hello, Muhammad, > > On Thu, Mar 09, 2023 at 06:57:12PM +0500, Muhammad Usama Anjum wrote: >> Add new WP Async mode (UFFD_FEATURE_WP_ASYNC) which resolves the page >> faults on its own. It can be used to track that which pages have been >> written-to from the time the pages were write-protected. It is very >> efficient way to track the changes as uffd is by nature pte/pmd based. >> >> UFFD synchronous WP sends the page faults to the userspace where the >> pages which have been written-to can be tracked. But it is not efficient. >> This is why this asynchronous version is being added. After setting the >> WP Async, the pages which have been written to can be found in the pagemap >> file or information can be obtained from the PAGEMAP_IOCTL. >> >> Suggested-by: Peter Xu <peterx@xxxxxxxxxx> >> Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx> > > Here's the patch that can enable WP_ASYNC for all kinds of memories (as I > promised..). Currently I only tested btrfs (besides the common three) > which is the major fs I use locally, but I guess it'll also enable the rest > no matter what's underneath, just like soft-dirty. > > As I mentioned, I just feel it very unfortunate to have a lot of suffixes > for the UFFD_FEATURE_* on types of memory, and I hope we get rid of it for > this WP_ASYNC from the start because the workflow should really be similar > to anon/shmem handling for most of the rest, just a few tweaks here and > there. > > I had a feeling that some type of special VMA will work weirdly, but let's > see.. so far I don't come up with any. > > If the patch looks fine to you, please consider replace this patch with > patch 1 of mine where I attached. Then patch 1 can be reviewed alongside > with your series. > > Logically patch 1 can be reviewed separately too, because it works > perfectly afaiu without the atomic version of pagemap already. But on my > side I don't think it justifies anything really matters, so unless someone > thinks it a good idea to post / review / merge it separately, you can keep > that with your new pagemap ioctl. > > Patch 2 is only for your reference. It's not for merging quality so please > don't put it into your series. I do plan to cleanup the userfaultfd > selftests in the near future first (when I wrote this I am more eager to do > so..). I also think your final pagemap test cases can cover quite a bit. > > Thanks, > -- BR, Muhammad Usama Anjum
