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Commit 32a8d26c authored by Li Dongyang's avatar Li Dongyang Committed by Konrad Rzeszutek Wilk
Browse files

xen-blkfront: add BLKIF_OP_DISCARD and discard request struct 



Now we use BLKIF_OP_DISCARD and add blkif_request_discard to blkif_request union,
the patch is taken from Owen Smith and Konrad, Thanks

Signed-off-by: default avatarOwen Smith <owen.smith@citrix.com>
Signed-off-by: default avatarLi Dongyang <lidongyang@novell.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 322a8b03

include/xen/interface/io/blkif.h

+36 −0
Original line number Diff line number Diff line
@@ -57,6 +57,36 @@ typedef uint64_t blkif_sector_t; 
 * "feature-flush-cache" node!

 */

#define BLKIF_OP_FLUSH_DISKCACHE   3



/*

 * Recognised only if "feature-discard" is present in backend xenbus info.

 * The "feature-discard" node contains a boolean indicating whether trim

 * (ATA) or unmap (SCSI) - conviently called discard requests are likely

 * to succeed or fail. Either way, a discard request

 * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by

 * the underlying block-device hardware. The boolean simply indicates whether

 * or not it is worthwhile for the frontend to attempt discard requests.

 * If a backend does not recognise BLKIF_OP_DISCARD, it should *not*

 * create the "feature-discard" node!

 *

 * Discard operation is a request for the underlying block device to mark

 * extents to be erased. However, discard does not guarantee that the blocks

 * will be erased from the device - it is just a hint to the device

 * controller that these blocks are no longer in use. What the device

 * controller does with that information is left to the controller.

 * Discard operations are passed with sector_number as the

 * sector index to begin discard operations at and nr_sectors as the number of

 * sectors to be discarded. The specified sectors should be discarded if the

 * underlying block device supports trim (ATA) or unmap (SCSI) operations,

 * or a BLKIF_RSP_EOPNOTSUPP  should be returned.

 * More information about trim/unmap operations at:

 * http://t13.org/Documents/UploadedDocuments/docs2008/

 *     e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc

 * http://www.seagate.com/staticfiles/support/disc/manuals/

 *     Interface%20manuals/100293068c.pdf

 */

#define BLKIF_OP_DISCARD           5



/*

 * Maximum scatter/gather segments per request.

 * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
@@ -74,6 +104,11 @@ struct blkif_request_rw { 
	} seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];

};



struct blkif_request_discard {

	blkif_sector_t sector_number;

	uint64_t nr_sectors;

};



struct blkif_request {

	uint8_t        operation;    /* BLKIF_OP_???                         */

	uint8_t        nr_segments;  /* number of segments                   */
@@ -81,6 +116,7 @@ struct blkif_request { 
	uint64_t       id;           /* private guest value, echoed in resp  */

	union {

		struct blkif_request_rw rw;

		struct blkif_request_discard discard;

	} u;

};