Re: [x86_64] 2.6.14-git13 mplayer fails with "v4l2: ioctl queue buffer failed: Bad address" (2 Nov 2005, 11 Nov 2005)

[Matti Aarnio]

On Sun, Nov 13, 2005 at 01:22:51AM +0300, Nickolay V. Shmyrev wrote:
> Hello all.
> 
> We have even found the hack that fix that problem:

A hack, but working one..
(for the small while that I tested it)

> Index: linux/drivers/media/video/video-buf.c
> ===================================================================
> RCS file: /cvs/video4linux/v4l-kernel/linux/drivers/media/video/video-buf.c,v
> retrieving revision 1.21
> diff -u -p -r1.21 video-buf.c
> --- linux/drivers/media/video/video-buf.c       16 Oct 2005 12:13:58 -0000
> +++ linux/drivers/media/video/video-buf.c       12 Nov 2005 22:19:13 -0000
> @@ -1248,7 +1248,7 @@ int videobuf_mmap_mapper(struct videobuf
>         map->end      = vma->vm_end;
>         map->q        = q;
>         vma->vm_ops   = &videobuf_vm_ops;
> -       vma->vm_flags |= VM_DONTEXPAND | VM_RESERVED;
> +       vma->vm_flags |= VM_DONTEXPAND;
>         vma->vm_flags &= ~VM_IO; /* using shared anonymous pages */
>         vma->vm_private_data = map;
>         dprintk(1,"mmap %p: q=%p %08lx-%08lx pgoff %08lx bufs %d-%d\n",
> 
> Somehow since 2.6.15-rc1 VM_RESERVED makes get_user_pages return EFAULT.
> I don't know the exact reason of that behavior and the correct way to fix
> that problem. Just kernel interfaces changed once again, the old
> point everyone knows. So if someone can explain it, that would be helpful.

This EFAULT rejection is due to change in  get_user_pages()  function
in mm/memory.c  file of  2.6.14-git2


@@ -945,8 +947,8 @@ int get_user_pages(struct task_struct *t
                        continue;
                }
 
-               if (!vma || (vma->vm_flags & VM_IO)
-                               || !(flags & vma->vm_flags))
+               if (!vma || (vma->vm_flags & (VM_IO | VM_RESERVED))
+                               || !(vm_flags & vma->vm_flags))
                        return i ? : -EFAULT;
 
                if (is_vm_hugetlb_page(vma)) {


I don't know how to use git tools to see, whose patch actually
did this particular change.


/Matti Aarnio
-
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