[PATCH] xen/gntdev: do not set VM_PFNMAP

[PATCH] xen/gntdev: do not set VM_PFNMAP

[Stefano Stabellini]

Since when we are using the m2p_override it is not true anymore that the
mmap'ed area doesn't have corresponsing struct pages.

Removing the VM_PFNMAP flag makes get_user_pages work on the mmap'ed user vma.
An example test case would be using a Xen userspace block backend
(QDISK) on a file on NFS using O_DIRECT.

The patch should be backported back to 2.6.38.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 drivers/xen/gntdev.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 99d8151..1ffd03b 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -722,7 +722,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 	vma->vm_flags |= VM_RESERVED|VM_DONTEXPAND;
 
 	if (use_ptemod)
-		vma->vm_flags |= VM_DONTCOPY|VM_PFNMAP;
+		vma->vm_flags |= VM_DONTCOPY;
 
 	vma->vm_private_data = map;
 
-- 
1.7.2.5

Re: [PATCH] xen/gntdev: do not set VM_PFNMAP

[Konrad Rzeszutek Wilk]

On Tue, Apr 03, 2012 at 12:25:02PM +0100, Stefano Stabellini wrote:
> Since when we are using the m2p_override it is not true anymore that the
        ^^^^ - get rid of that.
> mmap'ed area doesn't have corresponsing struct pages.

That reads to me as !!do struct page. Which comes out as:

"m2p_override_* API the mmap-ed are have corresponding struct pages' ?


> 
> Removing the VM_PFNMAP flag makes get_user_pages work on the mmap'ed user vma.
> An example test case would be using a Xen userspace block backend
> (QDISK) on a file on NFS using O_DIRECT.
> 
> The patch should be backported back to 2.6.38.

Add CC: stable@kernel.org then. But does this patch depend on other
patches?

> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> ---
>  drivers/xen/gntdev.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index 99d8151..1ffd03b 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -722,7 +722,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
>  	vma->vm_flags |= VM_RESERVED|VM_DONTEXPAND;
>  
>  	if (use_ptemod)
> -		vma->vm_flags |= VM_DONTCOPY|VM_PFNMAP;
> +		vma->vm_flags |= VM_DONTCOPY;
>  
>  	vma->vm_private_data = map;
>  
> -- 
> 1.7.2.5

Re: [PATCH] xen/gntdev: do not set VM_PFNMAP

[Stefano Stabellini]

On Tue, 3 Apr 2012, Konrad Rzeszutek Wilk wrote:
> On Tue, Apr 03, 2012 at 12:25:02PM +0100, Stefano Stabellini wrote:
> > Since when we are using the m2p_override it is not true anymore that the
>         ^^^^ - get rid of that.
> > mmap'ed area doesn't have corresponsing struct pages.
> 
> That reads to me as !!do struct page. Which comes out as:
> 
> "m2p_override_* API the mmap-ed are have corresponding struct pages' ?

Yes, indeed: m2p_override_* provides the corresponding struct pages


> > Removing the VM_PFNMAP flag makes get_user_pages work on the mmap'ed user vma.
> > An example test case would be using a Xen userspace block backend
> > (QDISK) on a file on NFS using O_DIRECT.
> > 
> > The patch should be backported back to 2.6.38.
> 
> Add CC: stable@kernel.org then.

I'll resend CCing stable


> But does this patch depend on other
> patches?

only on the m2p_override, that is in Linux since 2.6.38