ALSA: Fix vunmap and free order in snd_free_sgbuf_pages()

In snd_free_sgbuf_pags(), vunmap() is called after releasing the SG
pages, and it causes errors on Xen as Xen manages the pages
differently.  Although no significant errors have been reported on
the actual hardware, this order should be fixed other way round,
first vunmap() then free pages.

Cc: Jan Beulich <jbeulich@novell.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 4 insertions, 3 deletions

diff --git a/sound/core/sgbuf.c b/sound/core/sgbuf.c
index d4564edd61d7..4e7ec2b49873 100644
--- a/sound/core/sgbuf.c
+++ b/sound/core/sgbuf.c
@@ -38,6 +38,10 @@ int snd_free_sgbuf_pages(struct snd_dma_buffer *dmab)
         if (! sgbuf)
                 return -EINVAL;
 
+        if (dmab->area)
+                vunmap(dmab->area);
+        dmab->area = NULL;
+
         tmpb.dev.type = SNDRV_DMA_TYPE_DEV;
         tmpb.dev.dev = sgbuf->dev;
         for (i = 0; i < sgbuf->pages; i++) {
@@ -48,9 +52,6 @@ int snd_free_sgbuf_pages(struct snd_dma_buffer *dmab)
                 tmpb.bytes = (sgbuf->table[i].addr & ~PAGE_MASK) << PAGE_SHIFT;
                 snd_dma_free_pages(&tmpb);
         }
-        if (dmab->area)
-                vunmap(dmab->area);
-        dmab->area = NULL;
 
         kfree(sgbuf->table);
         kfree(sgbuf->page_table);