[PATCH] unpaged: sound nopage get_page

Something noticed when studying use of VM_RESERVED in different drivers:
snd_usX2Y_hwdep_pcm_vm_nopage omitted to get_page: fixed.

And how did this work before? Aargh! That nopage is returning a page from
within a buffer allocated by snd_malloc_pages, which allocates a high-order
page, then does SetPageReserved on each 0-order page within.

That would have worked in 2.6.14, because when the area was unmapped,
PageReserved inhibited put_page. 2.6.15-rc1 removed that inhibition (while
leaving ineffective PageReserveds around for now), but it hasn't caused
trouble because.. we've not been freeing from VM_RESERVED at all.

Signed-off-by: Hugh Dickins <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

sound/usb/usx2y/usx2yhwdeppcm.c

···
 	snd_assert((offset % PAGE_SIZE) == 0, return NOPAGE_OOM);
 	vaddr = (char*)((usX2Ydev_t*)area->vm_private_data)->hwdep_pcm_shm + offset;
 	page = virt_to_page(vaddr);
+	get_page(page);
 
 	if (type)
 		*type = VM_FAULT_MINOR;