From: Ian Jackson <ian.jackson@eu.citrix.com>
Date: Mon, 2 Mar 2009 11:21:51 +0000 (+0000)
Subject: Override default cache mode for disk images to write-back
X-Git-Tag: t.master-before-merge
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=82787c6f689d869ad349df83ec3f58702afe00fe;p=qemu-xen-3.4-testing.git

Override default cache mode for disk images to write-back

Upstream qemu changed the default cache mode to write-through (ie,
O_DSYNC) which is much slower.  We do not need this as we have
explicit control of cacheing with the IDE cache control commands.

Original patch by Yang Zhang modified by Ian Jackson.

Signed-off-by: Yang Zhang <yang.zhang@intel.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
---

diff --git a/xenstore.c b/xenstore.c
index 6bfcdbbb..928e950c 100644
--- a/xenstore.c
+++ b/xenstore.c
@@ -472,7 +472,7 @@ void xenstore_parse_domain_config(int hvm_domid)
 #ifdef CONFIG_STUBDOM
         if (pasprintf(&danger_buf, "%s/device/vbd/%s", danger_path, e_danger[i]) == -1)
             continue;
-	if (bdrv_open2(bs, danger_buf, 0 /* snapshot */, &bdrv_vbd) == 0) {
+	if (bdrv_open2(bs, danger_buf, BDRV_O_CACHE_WB /* snapshot and write-back */, &bdrv_vbd) == 0) {
 	    pstrcpy(bs->filename, sizeof(bs->filename), params);
 	} else
 #endif
@@ -498,7 +498,7 @@ void xenstore_parse_domain_config(int hvm_domid)
 		}
 	    }
             pstrcpy(bs->filename, sizeof(bs->filename), params);
-            if (bdrv_open2(bs, params, 0 /* snapshot */, format) < 0)
+            if (bdrv_open2(bs, params, BDRV_O_CACHE_WB /* snapshot and write-back */, format) < 0)
                 fprintf(stderr, "qemu: could not open vbd '%s' or hard disk image '%s' (drv '%s' format '%s')\n", buf, params, drv ? drv : "?", format ? format->format_name : "0");
         }