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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;
* "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;
};