From 3175aa9f485cd6c65788b9b9e15039f81e54ab59 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Fri, 1 Feb 2019 14:20:16 -0800 Subject: [PATCH] mm/hugetlb.c: teach follow_hugetlb_page() to handle FOLL_NOWAIT hugetlb needs the same fix as faultin_nopage (which was applied in commit 2c437cf69e7f ("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: 0bcf0fa53e20 ("kvm: switch get_user_page_nowait() to get_user_pages_unlocked()") Signed-off-by: Andrea Arcangeli Tested-by: "Dr. David Alan Gilbert" Reported-by: "Dr. David Alan Gilbert" Reviewed-by: Mike Kravetz Reviewed-by: Peter Xu Cc: Mike Rapoport Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/hugetlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index df2e7dd5ff17f..afef61656c1e1 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4268,7 +4268,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, break; } if (ret & VM_FAULT_RETRY) { - if (nonblocking) + if (nonblocking && + !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) *nonblocking = 0; *nr_pages = 0; /* -- 2.39.5