qemu/0015-xen_disk-Add-suse-specific-flush-di.patch

From: Bruce Rogers <brogers@suse.com>
Date: Wed, 9 Mar 2016 15:18:11 -0700
Subject: xen_disk: Add suse specific flush disable handling and map to QEMU
 equiv

Add code to read the suse specific suse-diskcache-disable-flush flag out
of xenstore, and set the equivalent flag within QEMU.

Patch taken from Xen's patch queue, Olaf Hering being the original author.
[bsc#879425]

[BR: minor edits to pass qemu's checkpatch script]
Signed-off-by: Bruce Rogers <brogers@suse.com>
Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
 hw/block/xen_disk.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 36eff94f84..ddd5c7cbfd 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -90,6 +90,8 @@ struct XenBlkDev {
     int                 requests_finished;
     unsigned int        max_requests;
 
+    gboolean            cache_unsafe;
+    /* Persistent grants extension */
     gboolean            feature_discard;
 
     /* qemu block driver */
@@ -642,6 +644,18 @@ static void blk_parse_discard(struct XenBlkDev *blkdev)
     }
 }
 
+static void blk_parse_cache_unsafe(struct XenBlkDev *blkdev)
+{
+    int enable;
+
+    blkdev->cache_unsafe = false;
+
+    if (xenstore_read_be_int(&blkdev->xendev, "suse-diskcache-disable-flush",
+        &enable) == 0) {
+        blkdev->cache_unsafe = !!enable;
+    }
+}
+
 static int blk_init(struct XenDevice *xendev)
 {
     struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
@@ -717,6 +731,7 @@ static int blk_init(struct XenDevice *xendev)
                           MAX_RING_PAGE_ORDER);
 
     blk_parse_discard(blkdev);
+    blk_parse_cache_unsafe(blkdev);
 
     g_free(directiosafe);
     return 0;
@@ -764,6 +779,10 @@ static int blk_connect(struct XenDevice *xendev)
         qflags |= BDRV_O_UNMAP;
     }
 
+    if (blkdev->cache_unsafe) {
+        qflags |= BDRV_O_NO_FLUSH;
+    }
+
     /* init qemu block driver */
     index = (xendev->dev - 202 * 256) / 16;
     blkdev->dinfo = drive_get(IF_XEN, 0, index);