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, 31 insertions, 10 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 2c2c4be..351ddef 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -98,7 +98,8 @@ struct blkfront_info
 	unsigned long shadow_free;
 	unsigned int feature_flush;
 	unsigned int flush_op;
-	unsigned int feature_discard;
+	unsigned int feature_discard:1;
+	unsigned int feature_secdiscard:1;
 	unsigned int discard_granularity;
 	unsigned int discard_alignment;
 	int is_ready;
@@ -305,11 +306,14 @@ static int blkif_queue_request(struct request *req)
 		ring_req->operation = info->flush_op;
 	}
 
-	if (unlikely(req->cmd_flags & REQ_DISCARD)) {
+	if (unlikely(req->cmd_flags & (REQ_DISCARD | REQ_SECURE))) {
 		/* id, sector_number and handle are set above. */
 		ring_req->operation = BLKIF_OP_DISCARD;
-		ring_req->u.discard.nr_segments = 0;
 		ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
+		if ((req->cmd_flags & REQ_SECURE) && info->feature_secdiscard)
+			ring_req->u.discard.flag = BLKIF_DISCARD_SECURE;
+		else
+			ring_req->u.discard.flag = 0;
 	} else {
 		ring_req->u.rw.nr_segments = blk_rq_map_sg(req->q, req,
 							   info->sg);
@@ -426,6 +430,8 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
 		blk_queue_max_discard_sectors(rq, get_capacity(gd));
 		rq->limits.discard_granularity = info->discard_granularity;
 		rq->limits.discard_alignment = info->discard_alignment;
+		if (info->feature_secdiscard)
+			queue_flag_set_unlocked(QUEUE_FLAG_SECDISCARD, rq);
 	}
 
 	/* Hard sector size and max sectors impersonate the equiv. hardware. */
@@ -707,6 +713,8 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 static void blkif_completion(struct blk_shadow *s)
 {
 	int i;
+	/* Do not let BLKIF_OP_DISCARD as nr_segment is in the same place
+	 * flag. */
 	for (i = 0; i < s->req.u.rw.nr_segments; i++)
 		gnttab_end_foreign_access(s->req.u.rw.seg[i].gref, 0, 0UL);
 }
@@ -738,7 +746,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 		id   = bret->id;
 		req  = info->shadow[id].request;
 
-		blkif_completion(&info->shadow[id]);
+		if (bret->operation != BLKIF_OP_DISCARD)
+			blkif_completion(&info->shadow[id]);
 
 		add_id_to_freelist(info, id);
 
@@ -751,7 +760,9 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 					   info->gd->disk_name);
 				error = -EOPNOTSUPP;
 				info->feature_discard = 0;
+				info->feature_secdiscard = 0;
 				queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
+				queue_flag_clear(QUEUE_FLAG_SECDISCARD, rq);
 			}
 			__blk_end_request_all(req, error);
 			break;
@@ -1039,13 +1050,15 @@ static int blkif_recover(struct blkfront_info *info)
 		req->u.rw.id = get_id_from_freelist(info);
 		memcpy(&info->shadow[req->u.rw.id], &copy[i], sizeof(copy[i]));
 
+		if (req->operation != BLKIF_OP_DISCARD) {
 		/* Rewrite any grant references invalidated by susp/resume. */
-		for (j = 0; j < req->u.rw.nr_segments; j++)
-			gnttab_grant_foreign_access_ref(
-				req->u.rw.seg[j].gref,
-				info->xbdev->otherend_id,
-				pfn_to_mfn(info->shadow[req->u.rw.id].frame[j]),
-				rq_data_dir(info->shadow[req->u.rw.id].request));
+			for (j = 0; j < req->u.rw.nr_segments; j++)
+				gnttab_grant_foreign_access_ref(
+					req->u.rw.seg[j].gref,
+					info->xbdev->otherend_id,
+					pfn_to_mfn(info->shadow[req->u.rw.id].frame[j]),
+					rq_data_dir(info->shadow[req->u.rw.id].request));
+		}
 		info->shadow[req->u.rw.id].req = *req;
 
 		info->ring.req_prod_pvt++;
@@ -1137,11 +1150,13 @@ static void blkfront_setup_discard(struct blkfront_info *info)
 	char *type;
 	unsigned int discard_granularity;
 	unsigned int discard_alignment;
+	unsigned int discard_secure;
 
 	type = xenbus_read(XBT_NIL, info->xbdev->otherend, "type", NULL);
 	if (IS_ERR(type))
 		return;
 
+	info->feature_secdiscard = 0;
 	if (strncmp(type, "phy", 3) == 0) {
 		err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
 			"discard-granularity", "%u", &discard_granularity,
@@ -1152,6 +1167,12 @@ static void blkfront_setup_discard(struct blkfront_info *info)
 			info->discard_granularity = discard_granularity;
 			info->discard_alignment = discard_alignment;
 		}
+		err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "discard-secure", "%d", &discard_secure,
+			    NULL);
+		if (!err)
+			info->feature_secdiscard = discard_secure;
+
 	} else if (strncmp(type, "file", 4) == 0)
 		info->feature_discard = 1;