gfs2: Don't withdraw under a spin lock

In two places, the gfs2_io_error_bh macro is called while holding the
sd_ail_lock spin lock.  This isn't allowed because gfs2_io_error_bh
withdraws the filesystem, which can sleep because it issues a uevent.
To fix that, add a gfs2_io_error_bh_wd macro that does withdraw the
filesystem and change gfs2_io_error_bh to not withdraw the filesystem.
In those places where the new gfs2_io_error_bh is used, withdraw the
filesystem after releasing sd_ail_lock.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Andrew Price <anprice@redhat.com>
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 4d65679..f2567f9 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -49,7 +49,7 @@
 	if (test_set_buffer_pinned(bh))
 		gfs2_assert_withdraw(sdp, 0);
 	if (!buffer_uptodate(bh))
-		gfs2_io_error_bh(sdp, bh);
+		gfs2_io_error_bh_wd(sdp, bh);
 	bd = bh->b_private;
 	/* If this buffer is in the AIL and it has already been written
 	 * to in-place disk block, remove it from the AIL.