• Peter Xu's avatar
    userfaultfd: wp: support swap and page migration · f45ec5ff
    Peter Xu authored
    For either swap and page migration, we all use the bit 2 of the entry to
    identify whether this entry is uffd write-protected.  It plays a similar
    role as the existing soft dirty bit in swap entries but only for keeping
    the uffd-wp tracking for a specific PTE/PMD.
    
    Something special here is that when we want to recover the uffd-wp bit
    from a swap/migration entry to the PTE bit we'll also need to take care of
    the _PAGE_RW bit and make sure it's cleared, otherwise even with the
    _PAGE_UFFD_WP bit we can't trap it at all.
    
    In change_pte_range() we do nothing for uffd if the PTE is a swap entry.
    That can lead to data mismatch if the page that we are going to write
    protect is swapped out when sending the UFFDIO_WRITEPROTECT.  This patch
    also applies/removes the uffd-wp bit even for the swap entries.
    Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    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: Mike Rapoport <rppt@linux.vnet.ibm.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/20200220163112.11409-11-peterx@redhat.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    f45ec5ff
memory.c 132 KB