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Commit 47dd9245 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds
Browse files

userfaultfd: hugetlbfs: UFFD_FEATURE_MISSING_SHMEM 

Userland developers asked to be notified immediately by the UFFDIO_API
ioctl if shmem missing mode is supported by userfaultfd in the running
kernel.  This avoids the need to run UFFDIO_REGISTER on a shmem virtual
memory range to find out.

Link: http://lkml.kernel.org/r/20161216144821.5183-38-aarcange@redhat.com


Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cb658a45

include/uapi/linux/userfaultfd.h

+7 −1
Original line number Diff line number Diff line
@@ -21,7 +21,8 @@ 
#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK |		\

			   UFFD_FEATURE_EVENT_REMAP |		\

			   UFFD_FEATURE_EVENT_MADVDONTNEED |	\

			   UFFD_FEATURE_MISSING_HUGETLBFS)

			   UFFD_FEATURE_MISSING_HUGETLBFS |	\

			   UFFD_FEATURE_MISSING_SHMEM)

#define UFFD_API_IOCTLS				\

	((__u64)1 << _UFFDIO_REGISTER |		\

	 (__u64)1 << _UFFDIO_UNREGISTER |	\
@@ -146,12 +147,17 @@ struct uffdio_api { 
	 *    it, so userland can later check if the feature flag is

	 *    present in uffdio_api.features after UFFDIO_API

	 *    succeeded.

	 *

	 * UFFD_FEATURE_MISSING_SHMEM works the same as

	 * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem

	 * (i.e. tmpfs and other shmem based APIs).

	 */

#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)

#define UFFD_FEATURE_MISSING_SHMEM		(1<<5)

	__u64 features;



	__u64 ioctls;