xen/blkback: Add support for BLKIF_OP_FLUSH_DISKCACHE and drop BLKIF_OP_WRITE_BARRIER.

We drop the support for 'feature-barrier' and add in the support
for the 'feature-flush-cache' if the real backend storage supports
flushing.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 64b0a1c760fb..9adcf806f83f 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -276,7 +276,7 @@ int __init xen_blkif_interface_init(void)
 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
-VBD_SHOW(br_req,  "%d\n", be->blkif->st_br_req);
+VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 
@@ -284,7 +284,7 @@ static struct attribute *vbdstat_attrs[] = {
         &dev_attr_oo_req.attr,
         &dev_attr_rd_req.attr,
         &dev_attr_wr_req.attr,
-        &dev_attr_br_req.attr,
+        &dev_attr_f_req.attr,
         &dev_attr_rd_sect.attr,
         &dev_attr_wr_sect.attr,
         NULL
@@ -343,6 +343,7 @@ static int vbd_create(struct blkif_st *blkif, blkif_vdev_t handle,
 {
         struct vbd *vbd;
         struct block_device *bdev;
+        struct request_queue *q;
 
         vbd = &blkif->vbd;
         vbd->handle   = handle;
@@ -375,6 +376,10 @@ static int vbd_create(struct blkif_st *blkif, blkif_vdev_t handle,
         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
                 vbd->type |= VDISK_REMOVABLE;
 
+        q = bdev_get_queue(bdev);
+        if (q && q->flush_flags)
+                vbd->flush_support = true;
+
         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
                 handle, blkif->domid);
         return 0;
@@ -406,16 +411,16 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
         return 0;
 }
 
-int xen_blkbk_barrier(struct xenbus_transaction xbt,
-                      struct backend_info *be, int state)
+int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
+                              struct backend_info *be, int state)
 {
         struct xenbus_device *dev = be->dev;
         int err;
 
-        err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
+        err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
                             "%d", state);
         if (err)
-                xenbus_dev_fatal(dev, err, "writing feature-barrier");
+                xenbus_dev_fatal(dev, err, "writing feature-flush-cache");
 
         return err;
 }
@@ -642,7 +647,7 @@ again:
                 return;
         }
 
-        err = xen_blkbk_barrier(xbt, be, 1);
+        err = xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
         if (err)
                 goto abort;