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>
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@@ -84,6 +84,21 @@ typedef uint64_t blkif_sector_t;
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* e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
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* http://www.seagate.com/staticfiles/support/disc/manuals/
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* Interface%20manuals/100293068c.pdf
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* The backend can optionally provide three extra XenBus attributes to
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* further optimize the discard functionality:
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* 'discard-aligment' - Devices that support discard functionality may
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* internally allocate space in units that are bigger than the exported
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* logical block size. The discard-alignment parameter indicates how many bytes
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* the beginning of the partition is offset from the internal allocation unit's
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* natural alignment.
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* 'discard-granularity' - Devices that support discard functionality may
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* internally allocate space using units that are bigger than the logical block
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* size. The discard-granularity parameter indicates the size of the internal
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* allocation unit in bytes if reported by the device. Otherwise the
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* discard-granularity will be set to match the device's physical block size.
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* 'discard-secure' - All copies of the discarded sectors (potentially created
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* by garbage collection) must also be erased. To use this feature, the flag
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* BLKIF_DISCARD_SECURE must be set in the blkif_request_trim.
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*/
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#define BLKIF_OP_DISCARD 5
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@@ -111,7 +126,8 @@ struct blkif_request_rw {
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} __attribute__((__packed__));
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struct blkif_request_discard {
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uint8_t nr_segments; /* number of segments */
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uint8_t flag; /* BLKIF_DISCARD_SECURE or zero. */
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#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */
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blkif_vdev_t _pad1; /* only for read/write requests */
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#ifdef CONFIG_X86_64
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uint32_t _pad2; /* offsetof(blkif_req..,u.discard.id)==8*/
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