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.
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
include/uapi/linux/userfaultfd.h | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 10631a4..9ac4b68 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -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;
--
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