ALSA: us122l: Fix pcm_usb_stream mmapping regression

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@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 3 insertions, 1 deletions

diff --git a/sound/usb/usx2y/us122l.c b/sound/usb/usx2y/us122l.c
index d0323a693ba2..999550bbad40 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: