forked from luck/tmp_suning_uos_patched
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>
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@ -57,6 +57,36 @@ typedef uint64_t blkif_sector_t;
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* "feature-flush-cache" node!
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*/
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#define BLKIF_OP_FLUSH_DISKCACHE 3
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/*
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* Recognised only if "feature-discard" is present in backend xenbus info.
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* The "feature-discard" node contains a boolean indicating whether trim
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* (ATA) or unmap (SCSI) - conviently called discard requests are likely
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* to succeed or fail. Either way, a discard request
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* may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
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* the underlying block-device hardware. The boolean simply indicates whether
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* or not it is worthwhile for the frontend to attempt discard requests.
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* If a backend does not recognise BLKIF_OP_DISCARD, it should *not*
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* create the "feature-discard" node!
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*
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* Discard operation is a request for the underlying block device to mark
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* extents to be erased. However, discard does not guarantee that the blocks
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* will be erased from the device - it is just a hint to the device
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* controller that these blocks are no longer in use. What the device
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* controller does with that information is left to the controller.
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* Discard operations are passed with sector_number as the
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* sector index to begin discard operations at and nr_sectors as the number of
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* sectors to be discarded. The specified sectors should be discarded if the
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* underlying block device supports trim (ATA) or unmap (SCSI) operations,
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* or a BLKIF_RSP_EOPNOTSUPP should be returned.
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* More information about trim/unmap operations at:
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* http://t13.org/Documents/UploadedDocuments/docs2008/
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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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*/
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#define BLKIF_OP_DISCARD 5
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/*
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* Maximum scatter/gather segments per request.
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* This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
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@ -74,6 +104,11 @@ struct blkif_request_rw {
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} seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
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};
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struct blkif_request_discard {
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blkif_sector_t sector_number;
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uint64_t nr_sectors;
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};
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struct blkif_request {
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uint8_t operation; /* BLKIF_OP_??? */
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uint8_t nr_segments; /* number of segments */
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@ -81,6 +116,7 @@ struct blkif_request {
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uint64_t id; /* private guest value, echoed in resp */
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union {
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struct blkif_request_rw rw;
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struct blkif_request_discard discard;
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} u;
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};
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