userfaultfd.2: Update on write-protection support

The shmem/hugetlbfs memory types are supported for write-protection
messages very lately.  Update the man page to reflect that.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>

diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
index 6b9412aafcd2ec50313df794d671512a78990c3f..9b5ec03585b040bc07b05f33e3aadc8989ff35a5 100644 (file)
--- a/man2/userfaultfd.2
+++ b/man2/userfaultfd.2
@@ -270,13 +270,18 @@ Since Linux 4.11,
 userfaultfd can be also used with hugetlbfs and shared memory mappings.
 .\"
 .SS Userfaultfd write-protect mode (since 5.7)
-Since Linux 5.7, userfaultfd supports write-protect mode.
+Since Linux 5.7, userfaultfd supports write-protect mode for anonymous memory.
 The user needs to first check availability of this feature using
 .B UFFDIO_API
 ioctl against the feature bit
 .B UFFD_FEATURE_PAGEFAULT_FLAG_WP
 before using this feature.
 .PP
+Since Linux 5.19, the write-protection mode was also supported on shmem and hugetlbfs
+memory types.
+It can be detected with the feature bit
+.BR UFFD_FEATURE_WP_HUGETLBFS_SHMEM .
+.PP
 To register with userfaultfd write-protect mode, the user needs to initiate the
 .B UFFDIO_REGISTER
 ioctl with mode
@@ -327,8 +332,6 @@ ioctl, whose
 should have the flag
 .B UFFDIO_WRITEPROTECT_MODE_WP
 cleared upon the faulted page or range.
-.PP
-Write-protect mode supports only private anonymous memory.
 .\"
 .SS Userfaultfd minor fault mode (since 5.13)
 Since Linux 5.13,