The patch titled
Subject: userfaultfd: hugetlbfs: UFFD_FEATURE_MISSING_HUGETLBFS
has been added to the -mm tree. Its filename is
userfaultfd-hugetlbfs-uffd_feature_missing_hugetlbfs.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-hugetlbfs-uffd_feature_missing_hugetlbfs.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-hugetlbfs-uffd_feature_missing_hugetlbfs.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Subject: userfaultfd: hugetlbfs: UFFD_FEATURE_MISSING_HUGETLBFS
Userland developers asked to be notified immediately by the UFFDIO_API
ioctl if hugetlbfs missing mode is supported by userfaultfd in the running
kernel. This avoids the need to run UFFDIO_REGISTER on a hugetlbfs
virtual memory range to find out.
Link: http://lkml.kernel.org/r/20161216144821.5183-27-aarcange@xxxxxxxxxx
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Michael Rapoport <RAPOPORT@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/userfaultfd.h | 28 +++++++++++++++++++++++++---
1 file changed, 25 insertions(+), 3 deletions(-)
diff -puN include/uapi/linux/userfaultfd.h~userfaultfd-hugetlbfs-uffd_feature_missing_hugetlbfs include/uapi/linux/userfaultfd.h
--- a/include/uapi/linux/userfaultfd.h~userfaultfd-hugetlbfs-uffd_feature_missing_hugetlbfs
+++ a/include/uapi/linux/userfaultfd.h
@@ -18,9 +18,10 @@
* means the userland is reading).
*/
#define UFFD_API ((__u64)0xAA)
-#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \
- UFFD_FEATURE_EVENT_REMAP | \
- UFFD_FEATURE_EVENT_MADVDONTNEED)
+#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \
+ UFFD_FEATURE_EVENT_REMAP | \
+ UFFD_FEATURE_EVENT_MADVDONTNEED | \
+ UFFD_FEATURE_MISSING_HUGETLBFS)
#define UFFD_API_IOCTLS \
((__u64)1 << _UFFDIO_REGISTER | \
(__u64)1 << _UFFDIO_UNREGISTER | \
@@ -125,11 +126,32 @@ struct uffdio_api {
* Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
* are to be considered implicitly always enabled in all kernels as
* long as the uffdio_api.api requested matches UFFD_API.
+ *
+ * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
+ * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
+ * hugetlbfs virtual memory ranges. Adding or not adding
+ * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
+ * no real functional effect after UFFDIO_API returns, but
+ * it's only useful for an initial feature set probe at
+ * UFFDIO_API time. There are two ways to use it:
+ *
+ * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
+ * uffdio_api.features before calling UFFDIO_API, an error
+ * will be returned by UFFDIO_API on a kernel without
+ * hugetlbfs missing support
+ *
+ * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
+ * uffdio_api.features and instead it will be set by the
+ * kernel in the uffdio_api.features if the kernel supports
+ * it, so userland can later check if the feature flag is
+ * present in uffdio_api.features after UFFDIO_API
+ * succeeded.
*/
#define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0)
#define UFFD_FEATURE_EVENT_FORK (1<<1)
#define UFFD_FEATURE_EVENT_REMAP (1<<2)
#define UFFD_FEATURE_EVENT_MADVDONTNEED (1<<3)
+#define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4)
__u64 features;
__u64 ioctls;
_
Patches currently in -mm which might be from aarcange@xxxxxxxxxx are
userfaultfd-document-_ior-_iow.patch
userfaultfd-correct-comment-about-uffd_feature_pagefault_flag_wp.patch
userfaultfd-convert-bug-to-warn_on_once.patch
userfaultfd-use-vma_is_anonymous.patch
userfaultfd-non-cooperative-report-all-available-features-to-userland.patch
userfaultfd-non-cooperative-add-fork-event-build-warning-fix.patch
userfaultfd-non-cooperative-optimize-mremap_userfaultfd_complete.patch
userfaultfd-non-cooperative-avoid-madv_dontneed-race-condition.patch
userfaultfd-non-cooperative-wake-userfaults-after-uffdio_unregister.patch
userfaultfd-hugetlbfs-gup-support-vm_fault_retry.patch
userfaultfd-hugetlbfs-uffd_feature_missing_hugetlbfs.patch
userfaultfd-shmem-add-tlbflushh-header-for-microblaze.patch
userfaultfd-shmem-lock-the-page-before-adding-it-to-pagecache.patch
userfaultfd-shmem-avoid-leaking-blocks-and-used-blocks-in-uffdio_copy.patch
userfaultfd-hugetlbfs-uffd_feature_missing_shmem.patch
userfaultfd-selftest-test-uffdio_zeropage-on-all-memory-types.patch
mm-mprotect-use-pmd_trans_unstable-instead-of-taking-the-pmd_lock.patch
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