On 4/9/21 2:18 PM, Peter Xu wrote:
On Fri, Apr 09, 2021 at 10:03:53AM -0700, Axel Rasmussen wrote:
On Thu, Apr 8, 2021 at 10:04 PM Andrew Morton akpm@linux-foundation.org wrote:
On Thu, 8 Apr 2021 16:43:18 -0700 Axel Rasmussen axelrasmussen@google.com wrote:
The idea is that it will apply cleanly to akpm's tree, *replacing* the following patches (i.e., drop these first, and then apply this series):
userfaultfd-support-minor-fault-handling-for-shmem.patch userfaultfd-support-minor-fault-handling-for-shmem-fix.patch userfaultfd-support-minor-fault-handling-for-shmem-fix-2.patch userfaultfd-support-minor-fault-handling-for-shmem-fix-3.patch userfaultfd-support-minor-fault-handling-for-shmem-fix-4.patch userfaultfd-selftests-use-memfd_create-for-shmem-test-type.patch userfaultfd-selftests-create-alias-mappings-in-the-shmem-test.patch userfaultfd-selftests-reinitialize-test-context-in-each-test.patch userfaultfd-selftests-exercise-minor-fault-handling-shmem-support.patch
Well. the problem is,
if (area_alias == MAP_FAILED)err("mmap of memfd alias failed");`err' doesn't exist until eleventy patches later, in Peter's "userfaultfd/selftests: unify error handling". I got tired of (and lost confidence in) replacing "err(...)" with "fprintf(stderr, ...); exit(1)" everywhere then fixing up the fallout when Peter's patch came along. Shudder.
Oof - sorry about that!
Sorry, all this material pretty clearly isn't going to make 5.12 (potentially nine days hence), so I shall drop all the userfaultfd patches. Let's take a fresh run at all of this after -rc1.
That's okay, my understanding was already that it certainly wouldn't be in the 5.12 release, but that we might be ready in time for 5.13.
I have tentatively retained the first series:
userfaultfd-add-minor-fault-registration-mode.patch userfaultfd-add-minor-fault-registration-mode-fix.patch userfaultfd-disable-huge-pmd-sharing-for-minor-registered-vmas.patch userfaultfd-hugetlbfs-only-compile-uffd-helpers-if-config-enabled.patch userfaultfd-add-uffdio_continue-ioctl.patch userfaultfd-update-documentation-to-describe-minor-fault-handling.patch userfaultfd-selftests-add-test-exercising-minor-fault-handling.patch
but I don't believe they have had much testing standalone, without the other userfaultfd patches present. So I don't think it's smart to upstream these in this cycle. Or I could drop them so you and Peter can have a clean shot at redoing the whole thing. Please let me know.
From my perspective, both Peter's error handling and the hugetlbfs minor faulting patches are ready to go. (Peter's most importantly; we should establish that as a base, and put all the burden on resolving conflicts with it on us instead of you :).)
My memory was that Peter's patch was applied before my shmem series, but it seems I was mistaken. So, maybe the best thing to do is to have Peter send a version of it based on your tree, without the shmem series? And then I'll resolve any conflicts in my tree?
It's true that we haven't tested the hugetlbfs minor faults patch extensively *with the shmem one also applied*, but it has had more thorough review than the shmem one at this point (e.g. by Mike Kravetz), and they're rather separate code paths (I'd be surprised if one breaks the other).
Yes I think the hugetlb part should have got more review done. IMHO it's a matter of whether Mike would still like to do a more thorough review, or seems okay to keep them.
I looked pretty closely at the hugetlb specific parts of the minor fault handling series. I only took a high level look at the code modifying and dealing with the userfaultfd API. The hugetlb specific parts looked fine to me. I can take a closer look at the userfaultfd API modifications, but it would take more time for me to come up to speed on the APIs.