• Cyrill Gorcunov's avatar
    mm: track vma changes with VM_SOFTDIRTY bit · d9104d1c
    Cyrill Gorcunov authored
    Pavel reported that in case if vma area get unmapped and then mapped (or
    expanded) in-place, the soft dirty tracker won't be able to recognize this
    situation since it works on pte level and ptes are get zapped on unmap,
    loosing soft dirty bit of course.
    
    So to resolve this situation we need to track actions on vma level, there
    VM_SOFTDIRTY flag comes in.  When new vma area created (or old expanded)
    we set this bit, and keep it here until application calls for clearing
    soft dirty bit.
    
    Thus when user space application track memory changes now it can detect if
    vma area is renewed.
    Reported-by: 's avatarPavel Emelyanov <xemul@parallels.com>
    Signed-off-by: 's avatarCyrill Gorcunov <gorcunov@openvz.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Matt Mackall <mpm@selenic.com>
    Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
    Cc: Marcelo Tosatti <mtosatti@redhat.com>
    Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
    Cc: Stephen Rothwell <sfr@canb.auug.org.au>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
    Cc: Rob Landley <rob@landley.net>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    d9104d1c