[SCSI] libosd: Support for scatter gather write/read commands

This patch adds the Scatter-Gather (sg) API to libosd.
Scatter-gather enables a write/read of multiple none-contiguous
areas of an object, in a single call. The extents may overlap
and/or be in any order.

The Scatter-Gather list is sent to the target in what is called
a "cdb continuation segment". This is yet another possible segment
in the osd-out-buffer. It is unlike all other segments in that it
sits before the actual "data" segment (which until now was always
first), and that it is signed by itself and not part of the data
buffer. This is because the cdb-continuation-segment is considered
a spill-over of the CDB data, and is therefor signed under
OSD_SEC_CAPKEY and higher.

TODO: A new osd_finalize_request_ex version should be supplied so
the @caps received on the network also contains a size parameter
and can be spilled over into the "cdb continuation segment".

Thanks to John Chandy <john.chandy@uconn.edu> for the original
code, and investigations. And the implementation of SG support
in the osd-target.

Original-coded-by: John Chandy <john.chandy@uconn.edu>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 42 insertions, 0 deletions

diff --git a/include/scsi/osd_protocol.h b/include/scsi/osd_protocol.h
index 685661283540..a6026da25f3e 100644
--- a/include/scsi/osd_protocol.h
+++ b/include/scsi/osd_protocol.h
@@ -631,4 +631,46 @@ static inline void osd_sec_set_caps(struct osd_capability_head *cap,
         put_unaligned_le16(bit_mask, &cap->permissions_bit_mask);
 }
 
+/* osd2r05a sec 5.3: CDB continuation segment formats */
+enum osd_continuation_segment_format {
+        CDB_CONTINUATION_FORMAT_V2 = 0x01,
+};
+
+struct osd_continuation_segment_header {
+        u8      format;
+        u8      reserved1;
+        __be16  service_action;
+        __be32  reserved2;
+        u8      integrity_check[OSDv2_CRYPTO_KEYID_SIZE];
+} __packed;
+
+/* osd2r05a sec 5.4.1: CDB continuation descriptors */
+enum osd_continuation_descriptor_type {
+        NO_MORE_DESCRIPTORS = 0x0000,
+        SCATTER_GATHER_LIST = 0x0001,
+        QUERY_LIST = 0x0002,
+        USER_OBJECT = 0x0003,
+        COPY_USER_OBJECT_SOURCE = 0x0101,
+        EXTENSION_CAPABILITIES = 0xFFEE
+};
+
+struct osd_continuation_descriptor_header {
+        __be16  type;
+        u8      reserved;
+        u8      pad_length;
+        __be32  length;
+} __packed;
+
+
+/* osd2r05a sec 5.4.2: Scatter/gather list */
+struct osd_sg_list_entry {
+        __be64 offset;
+        __be64 len;
+};
+
+struct osd_sg_continuation_descriptor {
+        struct osd_continuation_descriptor_header hdr;
+        struct osd_sg_list_entry entries[];
+};
+
 #endif /* ndef __OSD_PROTOCOL_H__ */