xen/blk[front|back]: Enhance discard support with secure erasing support.

Part of the blkdev_issue_discard(xx) operation is that it can also
issue a secure discard operation that will permanantly remove the
sectors in question. We advertise that we can support that via the
'discard-secure' attribute and on the request, if the 'secure' bit
is set, we will attempt to pass in REQ_DISCARD | REQ_SECURE.

CC: Li Dongyang <lidongyang@novell.com>
[v1: Used 'flag' instead of 'secure:1' bit]
[v2: Use 'reserved' uint8_t instead of adding a new value]
[v3: Check for nseg when mapping instead of operation]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index f759ad4584c3..187fd2c1a15d 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -338,6 +338,9 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
         if (q && q->flush_flags)
                 vbd->flush_support = true;
 
+        if (q && blk_queue_secdiscard(q))
+                vbd->discard_secure = true;
+
         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
                 handle, blkif->domid);
         return 0;
@@ -420,6 +423,15 @@ int xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
                                 state = 1;
                                 blkif->blk_backend_type = BLKIF_BACKEND_PHY;
                         }
+                        /* Optional. */
+                        err = xenbus_printf(xbt, dev->nodename,
+                                "discard-secure", "%d",
+                                blkif->vbd.discard_secure);
+                        if (err) {
+                                xenbus_dev_fatal(dev, err,
+                                        "writting discard-secure");
+                                goto kfree;
+                        }
                 }
         } else {
                 err = PTR_ERR(type);