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, 5 insertions, 2 deletions

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index dbfe7b3b0737..d0ee7edc9be8 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -69,7 +69,7 @@ struct blkif_x86_32_request_rw {
 } __attribute__((__packed__));
 
 struct blkif_x86_32_request_discard {
-        uint8_t        nr_segments;  /* number of segments                   */
+        uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
         blkif_vdev_t   _pad1;        /* was "handle" for read/write requests */
         uint64_t       id;           /* private guest value, echoed in resp  */
         blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
@@ -104,7 +104,7 @@ struct blkif_x86_64_request_rw {
 } __attribute__((__packed__));
 
 struct blkif_x86_64_request_discard {
-        uint8_t        nr_segments;  /* number of segments                   */
+        uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
         blkif_vdev_t   _pad1;        /* was "handle" for read/write requests */
         uint32_t       _pad2;        /* offsetof(blkif_..,u.discard.id)==8   */
         uint64_t       id;
@@ -164,6 +164,7 @@ struct xen_vbd {
         /* Cached size parameter. */
         sector_t                size;
         bool                    flush_support;
+        bool                    discard_secure;
 };
 
 struct backend_info;
@@ -261,6 +262,7 @@ static inline void blkif_get_x86_32_req(struct blkif_request *dst,
                         dst->u.rw.seg[i] = src->u.rw.seg[i];
                 break;
         case BLKIF_OP_DISCARD:
+                dst->u.discard.flag = src->u.discard.flag;
                 dst->u.discard.sector_number = src->u.discard.sector_number;
                 dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
                 break;
@@ -290,6 +292,7 @@ static inline void blkif_get_x86_64_req(struct blkif_request *dst,
                         dst->u.rw.seg[i] = src->u.rw.seg[i];
                 break;
         case BLKIF_OP_DISCARD:
+                dst->u.discard.flag = src->u.discard.flag;
                 dst->u.discard.sector_number = src->u.discard.sector_number;
                 dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
                 break;