Messages in this thread | | | Date | Mon, 10 Dec 2018 19:51:16 +0200 | From | Mike Rapoport <> | Subject | Re: [PATCH] userfaultfd: clear flag if remap event not enabled |
| |
On Mon, Dec 10, 2018 at 02:51:21PM +0800, Peter Xu wrote: > When the process being tracked do mremap() without > UFFD_FEATURE_EVENT_REMAP on the corresponding tracking uffd file > handle, we should not generate the remap event, and at the same > time we should clear all the uffd flags on the new VMA. Without > this patch, we can still have the VM_UFFD_MISSING|VM_UFFD_WP > flags on the new VMA even the fault handling process does not > even know the existance of the VMA. > > CC: Andrea Arcangeli <aarcange@redhat.com> > CC: Andrew Morton <akpm@linux-foundation.org> > CC: Mike Rapoport <rppt@linux.vnet.ibm.com> > CC: Kirill A. Shutemov <kirill@shutemov.name> > CC: Hugh Dickins <hughd@google.com> > CC: Pavel Emelyanov <xemul@virtuozzo.com> > CC: Pravin Shedge <pravin.shedge4linux@gmail.com> > CC: linux-mm@kvack.org > CC: linux-kernel@vger.kernel.org > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > fs/userfaultfd.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index cd58939dc977..798ae8a438ff 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -740,6 +740,9 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma, > vm_ctx->ctx = ctx; > userfaultfd_ctx_get(ctx); > WRITE_ONCE(ctx->mmap_changing, true); > + } else if (ctx) { > + vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; > + vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
My preference would be
if (!ctx) return; if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { ... } else { ... }
but I don't feel strongly about it.
I'd appreciate a comment in the code and with it
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
> } > } > > -- > 2.17.1 >
-- Sincerely yours, Mike.
| |