[PATCH 3.8 72/81] ALSA: us122l: Fix pcm_usb_stream mmapping regression

[Kamal Mostafa]

3.8.13.12 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai at suse.de>

commit ac536a848a1643e4b87e8fbd376a63091afc2ccc upstream.

The pcm_usb_stream plugin requires the mremap explicitly for the read
buffer, as it expands itself once after reading the required size.
But the commit [314e51b9: mm: kill vma flag VM_RESERVED and
mm->reserved_vm counter] converted blindly to a combination of
VM_DONTEXPAND | VM_DONTDUMP like other normal drivers, and this
resulted in the failure of mremap().

For fixing this regression, we need to remove VM_DONTEXPAND for the
read-buffer mmap.

Reported-and-tested-by: James Miller <jamesstewartmiller at gmail.com>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 sound/usb/usx2y/us122l.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/usb/usx2y/us122l.c b/sound/usb/usx2y/us122l.c
index d0323a6..999550b 100644
--- a/sound/usb/usx2y/us122l.c
+++ b/sound/usb/usx2y/us122l.c
@@ -262,7 +262,9 @@ static int usb_stream_hwdep_mmap(struct snd_hwdep *hw,
 	}
 
 	area->vm_ops = &usb_stream_hwdep_vm_ops;
-	area->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+	area->vm_flags |= VM_DONTDUMP;
+	if (!read)
+		area->vm_flags |= VM_DONTEXPAND;
 	area->vm_private_data = us122l;
 	atomic_inc(&us122l->mmap_count);
 out:
-- 
1.8.1.2