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-rw-r--r--include/xen/interface/io/blkif.h36
1 files changed, 36 insertions, 0 deletions
diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
index 3d5d6db864fe..9324488f23f0 100644
--- a/include/xen/interface/io/blkif.h
+++ b/include/xen/interface/io/blkif.h
@@ -57,6 +57,36 @@ typedef uint64_t blkif_sector_t;
57 * "feature-flush-cache" node! 57 * "feature-flush-cache" node!
58 */ 58 */
59#define BLKIF_OP_FLUSH_DISKCACHE 3 59#define BLKIF_OP_FLUSH_DISKCACHE 3
60
61/*
62 * Recognised only if "feature-discard" is present in backend xenbus info.
63 * The "feature-discard" node contains a boolean indicating whether trim
64 * (ATA) or unmap (SCSI) - conviently called discard requests are likely
65 * to succeed or fail. Either way, a discard request
66 * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
67 * the underlying block-device hardware. The boolean simply indicates whether
68 * or not it is worthwhile for the frontend to attempt discard requests.
69 * If a backend does not recognise BLKIF_OP_DISCARD, it should *not*
70 * create the "feature-discard" node!
71 *
72 * Discard operation is a request for the underlying block device to mark
73 * extents to be erased. However, discard does not guarantee that the blocks
74 * will be erased from the device - it is just a hint to the device
75 * controller that these blocks are no longer in use. What the device
76 * controller does with that information is left to the controller.
77 * Discard operations are passed with sector_number as the
78 * sector index to begin discard operations at and nr_sectors as the number of
79 * sectors to be discarded. The specified sectors should be discarded if the
80 * underlying block device supports trim (ATA) or unmap (SCSI) operations,
81 * or a BLKIF_RSP_EOPNOTSUPP should be returned.
82 * More information about trim/unmap operations at:
83 * http://t13.org/Documents/UploadedDocuments/docs2008/
84 * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
85 * http://www.seagate.com/staticfiles/support/disc/manuals/
86 * Interface%20manuals/100293068c.pdf
87 */
88#define BLKIF_OP_DISCARD 5
89
60/* 90/*
61 * Maximum scatter/gather segments per request. 91 * Maximum scatter/gather segments per request.
62 * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE. 92 * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
@@ -74,6 +104,11 @@ struct blkif_request_rw {
74 } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 104 } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
75}; 105};
76 106
107struct blkif_request_discard {
108 blkif_sector_t sector_number;
109 uint64_t nr_sectors;
110};
111
77struct blkif_request { 112struct blkif_request {
78 uint8_t operation; /* BLKIF_OP_??? */ 113 uint8_t operation; /* BLKIF_OP_??? */
79 uint8_t nr_segments; /* number of segments */ 114 uint8_t nr_segments; /* number of segments */
@@ -81,6 +116,7 @@ struct blkif_request {
81 uint64_t id; /* private guest value, echoed in resp */ 116 uint64_t id; /* private guest value, echoed in resp */
82 union { 117 union {
83 struct blkif_request_rw rw; 118 struct blkif_request_rw rw;
119 struct blkif_request_discard discard;
84 } u; 120 } u;
85}; 121};
86 122