userfaultfd: non-cooperative: closing the uffd without triggering SIGBUS
authorAndrea Arcangeli <aarcange@redhat.com>
Fri, 8 Sep 2017 23:12:42 +0000 (16:12 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 9 Sep 2017 01:26:47 +0000 (18:26 -0700)
commit656710a60e3693911bee3a355d2f2bbae3faba33
treedd55fb4c43f3cf65c50d0795a001370429b4d6e0
parent98c70baad4067cf3bfb90c26b3b01cb3eab621e2
userfaultfd: non-cooperative: closing the uffd without triggering SIGBUS

This is an enhancement to avoid a non cooperative userfaultfd manager
having to unregister all regions before it can close the uffd after all
userfaultfd activity completed.

The UFFDIO_UNREGISTER would serialize against the handle_userfault by
taking the mmap_sem for writing, but we can simply repeat the page fault
if we detect the uffd was closed and so the regular page fault paths
should takeover.

Link: http://lkml.kernel.org/r/20170823181227.19926-1-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/userfaultfd.c