PV-on-HVM: Do not enable barriers in blkfront before 2.6.16

Barrier support was rewritten after 2.6.15. Perhaps it would be
possible to implement support for old kernels as well but for now it
is easier to just disable them.

Signed-off-by: Ian Campbell <ian.campbell@xensource.com>

diff --git a/linux-2.6-xen-sparse/drivers/xen/blkfront/vbd.c b/linux-2.6-xen-sparse/drivers/xen/blkfront/vbd.c
index 7d8e11d1ec180e254753bf149fc0e839a34c74cf..f040a2b7e32e2df045cf93f069e69e5f328e5d5e 100644 (file)
--- a/linux-2.6-xen-sparse/drivers/xen/blkfront/vbd.c
+++ b/linux-2.6-xen-sparse/drivers/xen/blkfront/vbd.c
@@ -351,6 +351,7 @@ xlvbd_del(struct blkfront_info *info)
        info->rq = NULL;
 }
 
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,16)
 int
 xlvbd_barrier(struct blkfront_info *info)
 {
@@ -364,3 +365,11 @@ xlvbd_barrier(struct blkfront_info *info)
               info->gd->disk_name, info->feature_barrier ? "enabled" : "disabled");
        return 0;
 }
+#else
+int
+xlvbd_barrier(struct blkfront_info *info)
+{
+       printk("blkfront: %s: barriers disabled\n", info->gd->disk_name);
+       return -ENOSYS;
+}
+#endif