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Date: Tue, 8 Jan 2019 21:02:03 -0500 From: Andrea Arcangeli <aarcange@...hat.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...ux.vnet.ibm.com>, Mike Kravetz <mike.kravetz@...cle.com>, Peter Xu <peterx@...hat.com>, "Dr. David Alan Gilbert" <dgilbert@...hat.com> Subject: [PATCH 1/1] mm/hugetlb.c: teach follow_hugetlb_page() to handle FOLL_NOWAIT hugetlb needs the same fix as faultin_nopage (which was applied in 96312e61282ae3f6537a562625706498cbc75594) 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. Fixes: ce53053ce378 ("kvm: switch get_user_page_nowait() to get_user_pages_unlocked()") Signed-off-by: Andrea Arcangeli <aarcange@...hat.com> Tested-by: "Dr. David Alan Gilbert" <dgilbert@...hat.com> Reported-by: "Dr. David Alan Gilbert" <dgilbert@...hat.com> --- mm/hugetlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index e37efd5d8318..b3622d7888c8 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4301,7 +4301,8 @@ 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; /*
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