Commit 23080e27 authored Apr 06, 2020 by Peter Xu Committed by Linus Torvalds Apr 07, 2020

userfaultfd: wp: don't wake up when doing write protect



It does not make sense to try to wake up any waiting thread when we're
write-protecting a memory region.  Only wake up when resolving a write
protected page fault.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.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: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-16-peterx@redhat.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e06f1e1d

fs/userfaultfd.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -1812,6 +1812,7 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx,
		struct uffdio_writeprotect uffdio_wp;
		struct uffdio_writeprotect __user *user_uffdio_wp;
		struct userfaultfd_wake_range range;
		bool mode_wp, mode_dontwake;

		if (READ_ONCE(ctx->mmap_changing))
		return -EAGAIN;
		@@ -1830,18 +1831,20 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx,
		if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE \|
		UFFDIO_WRITEPROTECT_MODE_WP))
		return -EINVAL;
		if ((uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP) &&
		(uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE))

		mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP;
		mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE;

		if (mode_wp && mode_dontwake)
		return -EINVAL;

		ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start,
		uffdio_wp.range.len, uffdio_wp.mode &
		UFFDIO_WRITEPROTECT_MODE_WP,
		uffdio_wp.range.len, mode_wp,
		&ctx->mmap_changing);
		if (ret)
		return ret;

		if (!(uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE)) {
		if (!mode_wp && !mode_dontwake) {
		range.start = uffdio_wp.range.start;
		range.len = uffdio_wp.range.len;
		wake_userfault(ctx, &range);

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