mm/hugetlb.c: teach follow_hugetlb_page() to handle FOLL_NOWAIT

hugetlb needs the same fix as faultin_nopage (which was applied in commit 96312e6 ("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/[email protected] Fixes: ce53053 ("kvm: switch get_user_page_nowait() to get_user_pages_unlocked()") Signed-off-by: Andrea Arcangeli <[email protected]> Tested-by: "Dr. David Alan Gilbert" <[email protected]> Reported-by: "Dr. David Alan Gilbert" <[email protected]> Reviewed-by: Mike Kravetz <[email protected]> Reviewed-by: Peter Xu <[email protected]> Cc: Mike Rapoport <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
ambv · Feb 1, 2019 · 1ac2501 · 1ac2501
1 parent 36c0f7f
commit 1ac2501
Showing 1 changed file with 2 additions and 1 deletion.
diff --git 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;
 				/*