4.20-stable review patch. If anyone has any objections, please let me know.
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From: Andrea Arcangeli aarcange@redhat.com
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 | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4270,7 +4270,8 @@ long follow_hugetlb_page(struct mm_struc break; } if (ret & VM_FAULT_RETRY) { - if (nonblocking) + if (nonblocking && + !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) *nonblocking = 0; *nr_pages = 0; /*