Commit 4426e945 authored by Peter Xu's avatar Peter Xu Committed by Linus Torvalds
Browse files

mm/gup: allow VM_FAULT_RETRY for multiple times 



This is the gup counterpart of the change that allows the VM_FAULT_RETRY
to happen for more than once.  One thing to mention is that we must check
the fatal signal here before retry because the GUP can be interrupted by
that, otherwise we can loop forever.

Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Tested-by: default avatarBrian Geffon <bgeffon@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Link: http://lkml.kernel.org/r/20200220195357.16371-1-peterx@redhat.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4064b982

mm/gup.c

+21 −6
Original line number Diff line number Diff line
@@ -868,7 +868,10 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma, 
	if (*flags & FOLL_NOWAIT)

		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;

	if (*flags & FOLL_TRIED) {

		VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);

		/*

		 * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED

		 * can co-exist

		 */

		fault_flags |= FAULT_FLAG_TRIED;

	}
@@ -1228,7 +1231,6 @@ retry: 
		down_read(&mm->mmap_sem);

		if (!(fault_flags & FAULT_FLAG_TRIED)) {

			*unlocked = true;

			fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;

			fault_flags |= FAULT_FLAG_TRIED;

			goto retry;

		}
@@ -1312,17 +1314,30 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk, 
		if (likely(pages))

			pages += ret;

		start += ret << PAGE_SHIFT;

		lock_dropped = true;



retry:

		/*

		 * Repeat on the address that fired VM_FAULT_RETRY

		 * without FAULT_FLAG_ALLOW_RETRY but with

		 * FAULT_FLAG_TRIED.

		 * with both FAULT_FLAG_ALLOW_RETRY and

		 * FAULT_FLAG_TRIED.  Note that GUP can be interrupted

		 * by fatal signals, so we need to check it before we

		 * start trying again otherwise it can loop forever.

		 */



		if (fatal_signal_pending(current))

			break;



		*locked = 1;

		lock_dropped = true;

		down_read(&mm->mmap_sem);



		ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,

				       pages, NULL, NULL);

				       pages, NULL, locked);

		if (!*locked) {

			/* Continue to retry until we succeeded */

			BUG_ON(ret != 0);

			goto retry;

		}

		if (ret != 1) {

			BUG_ON(ret > 1);

			if (!pages_done)

mm/hugetlb.c

+4 −2
Original line number Diff line number Diff line
@@ -4349,8 +4349,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, 
				fault_flags |= FAULT_FLAG_ALLOW_RETRY |

					FAULT_FLAG_RETRY_NOWAIT;

			if (flags & FOLL_TRIED) {

				VM_WARN_ON_ONCE(fault_flags &

						FAULT_FLAG_ALLOW_RETRY);

				/*

				 * Note: FAULT_FLAG_ALLOW_RETRY and

				 * FAULT_FLAG_TRIED can co-exist

				 */

				fault_flags |= FAULT_FLAG_TRIED;

			}

			ret = hugetlb_fault(mm, vma, vaddr, fault_flags);

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