From: Peter Xu <peterx@xxxxxxxxxx> Subject: 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. Link: http://lkml.kernel.org/r/20200220163112.11409-16-peterx@xxxxxxxxxx Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Bobby Powers <bobbypowers@xxxxxxxxx> Cc: Brian Geffon <bgeffon@xxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Denis Plotnikov <dplotnikov@xxxxxxxxxxxxx> Cc: "Dr . David Alan Gilbert" <dgilbert@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Jerome Glisse <jglisse@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx> Cc: Martin Cracauer <cracauer@xxxxxxxx> Cc: Marty McFadden <mcfadden8@xxxxxxxx> Cc: Maya Gokhale <gokhale2@xxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Shaohua Li <shli@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/userfaultfd.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) --- a/fs/userfaultfd.c~userfaultfd-wp-dont-wake-up-when-doing-write-protect +++ a/fs/userfaultfd.c @@ -1812,6 +1812,7 @@ static int userfaultfd_writeprotect(stru 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(stru 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); _
