Re: SG does not ignore dxferp (direct io + mmap)

[Johannes Thumshirn <jthumshirn@suse.de>]

On Mon, Nov 21, 2016 at 01:24:02PM -0500, Ewan Milne wrote:
> On Mon, 2016-11-21 at 12:34 -0500, Douglas Gilbert wrote:
> > There was also this change which seems closer to the problem area:
> > 
> > commit 461c7fa126794157484dca48e88effa4963e3af3
> > Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > Date:   Tue Feb 2 16:57:35 2016 -0800
> > 
> >      drivers/scsi/sg.c: mark VMA as VM_IO to prevent migration
> > ...
> > 
> > diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> > index 503ab8b..5e82067 100644
> > --- a/drivers/scsi/sg.c
> > +++ b/drivers/scsi/sg.c
> > @@ -1261,7 +1261,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
> >          }
> > 
> >          sfp->mmap_called = 1;
> > -       vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
> > +       vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
> >          vma->vm_private_data = sfp;
> >          vma->vm_ops = &sg_mmap_vm_ops;
> >          return 0;
> > 
> > Doug Gilbert
> > 
> 
> Neither this change nor "sg: fix dxferp in from_to case" appears to
> fix the issue when applied on top of 4.4.  Still looking...

This brings bad memories from commit 2d99b55d3 back to live, but this is
applied on all test kernels I have.

I too will run some bisection as well now that we have an easy reproducer and
my timezone is somewhat ahead. Let's see if we can stretch the workday a bit.

Byte,
	Johannes

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Johannes Thumshirn                                          Storage
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