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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: Owen Smith <owen.smith@citrix.com>
Signed-off-by: Li Dongyang <lidongyang@novell.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Li Dongyang 2011-09-01 18:39:08 +08:00 committed by Konrad Rzeszutek Wilk
parent 322a8b0340
commit 32a8d26cc9
1 changed files with 36 additions and 0 deletions
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36
include/xen/interface/io/blkif.h
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@ -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;
};