[Xen-devel] [PATCH 3 of 3] interface: add 'discard-secure' and BLKIF_DISCARD_SECURE

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

# HG changeset patch
# User Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
# Date 1318457231 14400
# Node ID 50850daec7f0486ee7ca69b3d4cb58b4d340a5a7
# Parent  15c2d70dbac3e31c2d74b6700e1bb5f8a7d8256e
interface: add 'discard-secure' and BLKIF_DISCARD_SECURE

Alter the 'reserved' uint8_t to be used a 'flag'. We use only for
one flag: BLKIF_DISCARD_SECURE.

That flag can only be set if the backend has set 'discard-secure' to one.
If backend has not set 'discard-secure' to one, that flag will have no
effect.

Acked-by: Jan Beulich <JBeulich@xxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

diff -r 15c2d70dbac3 -r 50850daec7f0 xen/include/public/io/blkif.h
--- a/xen/include/public/io/blkif.h     Wed Oct 12 18:07:07 2011 -0400
+++ b/xen/include/public/io/blkif.h     Wed Oct 12 18:07:11 2011 -0400
@@ -107,7 +107,7 @@
  *     e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
  * http://www.seagate.com/staticfiles/support/disc/manuals/
  *     Interface%20manuals/100293068c.pdf
- * The backend can optionally provide two extra XenBus attributes to
+ * The backend can optionally provide three extra XenBus attributes to
  * further optimize the discard functionality:
  * 'discard-aligment' - Devices that support discard functionality may
  * internally allocate space in units that are bigger than the exported
@@ -119,6 +119,9 @@
  * size. The discard-granularity parameter indicates the size of the internal
  * allocation unit in bytes if reported by the device. Otherwise the
  * discard-granularity will be set to match the device's physical block size.
+ * 'discard-secure' - All copies of the discarded sectors (potentially created
+ * by garbage collection) must also be erased.  To use this feature, the flag
+ * BLKIF_DISCARD_SECURE must be set in the blkif_request_trim.
  */
 #define BLKIF_OP_DISCARD           5
 
@@ -159,7 +162,8 @@ typedef struct blkif_request blkif_reque
  */
 struct blkif_request_discard {
     uint8_t        operation;    /* BLKIF_OP_DISCARD                     */
-    uint8_t        reserved;     /*                                      */
+    uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
+#define BLKIF_DISCARD_SECURE (1<<0)  /* ignored if discard-secure=0      */
     blkif_vdev_t   handle;       /* same as for read/write requests      */
     uint64_t       id;           /* private guest value, echoed in resp  */
     blkif_sector_t sector_number;/* start sector idx on disk             */



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