mm/hugetlb.c: teach follow_hugetlb_page() to handle FOLL_NOWAIT
authorAndrea Arcangeli <aarcange@redhat.com>
Fri, 1 Feb 2019 22:20:16 +0000 (14:20 -0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 6 Feb 2019 16:30:14 +0000 (17:30 +0100)
commit15033ca6bd1379883ebd7533ba8feff4563c7f03
treeea9ca52e2f22b66996bd54f93e308144341fc32a
parentc7122344f9150289d053041081a07ce07de2a64f
mm/hugetlb.c: teach follow_hugetlb_page() to handle FOLL_NOWAIT

commit 1ac25013fb9e4ed595cd608a406191e93520881e upstream.

hugetlb needs the same fix as faultin_nopage (which was applied in
commit 96312e61282a ("mm/gup.c: teach get_user_pages_unlocked to handle
FOLL_NOWAIT")) or KVM hangs because it thinks the mmap_sem was already
released by hugetlb_fault() if it returned VM_FAULT_RETRY, but it wasn't
in the FOLL_NOWAIT case.

Link: http://lkml.kernel.org/r/20190109020203.26669-2-aarcange@redhat.com
Fixes: ce53053ce378 ("kvm: switch get_user_page_nowait() to get_user_pages_unlocked()")
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Tested-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Reported-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mm/hugetlb.c