[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 <[e-mail]> for the original
code, and investigations. And the implementation of SG support
in the osd-target.

Original-coded-by: John Chandy <[e-mail]>
Signed-off-by: Boaz Harrosh <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/osd/osd_initiator.c

···
 	_osd_free_seg(or, &or->get_attr);
 	_osd_free_seg(or, &or->enc_get_attr);
 	_osd_free_seg(or, &or->set_attr);
+	_osd_free_seg(or, &or->cdb_cont);
 
 	_osd_request_free(or);
 }
···
 	seg->buff = buff;
 	seg->alloc_size = max_bytes;
 	return 0;
+}
+
+static int _alloc_cdb_cont(struct osd_request *or, unsigned total_bytes)
+{
+	OSD_DEBUG("total_bytes=%d\n", total_bytes);
+	return _osd_realloc_seg(or, &or->cdb_cont, total_bytes);
 }
 
 static int _alloc_set_attr_list(struct osd_request *or,
···
 	return 0;
 }
 EXPORT_SYMBOL(osd_req_read_kern);
+
+static int _add_sg_continuation_descriptor(struct osd_request *or,
+	const struct osd_sg_entry *sglist, unsigned numentries, u64 *len)
+{
+	struct osd_sg_continuation_descriptor *oscd;
+	u32 oscd_size;
+	unsigned i;
+	int ret;
+
+	oscd_size = sizeof(*oscd) + numentries * sizeof(oscd->entries[0]);
+
+	if (!or->cdb_cont.total_bytes) {
+		/* First time, jump over the header, we will write to:
+		 *	cdb_cont.buff + cdb_cont.total_bytes
+		 */
+		or->cdb_cont.total_bytes =
+				sizeof(struct osd_continuation_segment_header);
+	}
+
+	ret = _alloc_cdb_cont(or, or->cdb_cont.total_bytes + oscd_size);
+	if (unlikely(ret))
+		return ret;
+
+	oscd = or->cdb_cont.buff + or->cdb_cont.total_bytes;
+	oscd->hdr.type = cpu_to_be16(SCATTER_GATHER_LIST);
+	oscd->hdr.pad_length = 0;
+	oscd->hdr.length = cpu_to_be32(oscd_size - sizeof(*oscd));
+
+	*len = 0;
+	/* copy the sg entries and convert to network byte order */
+	for (i = 0; i < numentries; i++) {
+		oscd->entries[i].offset = cpu_to_be64(sglist[i].offset);
+		oscd->entries[i].len    = cpu_to_be64(sglist[i].len);
+		*len += sglist[i].len;
+	}
+
+	or->cdb_cont.total_bytes += oscd_size;
+	OSD_DEBUG("total_bytes=%d oscd_size=%d numentries=%d\n",
+		  or->cdb_cont.total_bytes, oscd_size, numentries);
+	return 0;
+}
+
+static int _osd_req_finalize_cdb_cont(struct osd_request *or, const u8 *cap_key)
+{
+	struct request_queue *req_q = osd_request_queue(or->osd_dev);
+	struct bio *bio;
+	struct osd_cdb_head *cdbh = osd_cdb_head(&or->cdb);
+	struct osd_continuation_segment_header *cont_seg_hdr;
+
+	if (!or->cdb_cont.total_bytes)
+		return 0;
+
+	cont_seg_hdr = or->cdb_cont.buff;
+	cont_seg_hdr->format = CDB_CONTINUATION_FORMAT_V2;
+	cont_seg_hdr->service_action = cdbh->varlen_cdb.service_action;
+
+	/* create a bio for continuation segment */
+	bio = bio_map_kern(req_q, or->cdb_cont.buff, or->cdb_cont.total_bytes,
+			   GFP_KERNEL);
+	if (unlikely(!bio))
+		return -ENOMEM;
+
+	bio->bi_rw |= REQ_WRITE;
+
+	/* integrity check the continuation before the bio is linked
+	 * with the other data segments since the continuation
+	 * integrity is separate from the other data segments.
+	 */
+	osd_sec_sign_data(cont_seg_hdr->integrity_check, bio, cap_key);
+
+	cdbh->v2.cdb_continuation_length = cpu_to_be32(or->cdb_cont.total_bytes);
+
+	/* we can't use _req_append_segment, because we need to link in the
+	 * continuation bio to the head of the bio list - the
+	 * continuation segment (if it exists) is always the first segment in
+	 * the out data buffer.
+	 */
+	bio->bi_next = or->out.bio;
+	or->out.bio = bio;
+	or->out.total_bytes += or->cdb_cont.total_bytes;
+
+	return 0;
+}
+
+/* osd_req_write_sg: Takes a @bio that points to the data out buffer and an
+ * @sglist that has the scatter gather entries. Scatter-gather enables a write
+ * of multiple none-contiguous areas of an object, in a single call. The extents
+ * may overlap and/or be in any order. The only constrain is that:
+ *	total_bytes(sglist) >= total_bytes(bio)
+ */
+int osd_req_write_sg(struct osd_request *or,
+	const struct osd_obj_id *obj, struct bio *bio,
+	const struct osd_sg_entry *sglist, unsigned numentries)
+{
+	u64 len;
+	int ret = _add_sg_continuation_descriptor(or, sglist, numentries, &len);
+
+	if (ret)
+		return ret;
+	osd_req_write(or, obj, 0, bio, len);
+
+	return 0;
+}
+EXPORT_SYMBOL(osd_req_write_sg);
+
+/* osd_req_read_sg: Read multiple extents of an object into @bio
+ * See osd_req_write_sg
+ */
+int osd_req_read_sg(struct osd_request *or,
+	const struct osd_obj_id *obj, struct bio *bio,
+	const struct osd_sg_entry *sglist, unsigned numentries)
+{
+	u64 len;
+	int ret = _add_sg_continuation_descriptor(or, sglist, numentries, &len);
+
+	if (ret)
+		return ret;
+	osd_req_read(or, obj, 0, bio, len);
+
+	return 0;
+}
+EXPORT_SYMBOL(osd_req_read_sg);
 
 void osd_req_get_attributes(struct osd_request *or,
 	const struct osd_obj_id *obj)
···
 }
 
 static int _osd_req_finalize_data_integrity(struct osd_request *or,
-	bool has_in, bool has_out, u64 out_data_bytes, const u8 *cap_key)
+	bool has_in, bool has_out, struct bio *out_data_bio, u64 out_data_bytes,
+	const u8 *cap_key)
 {
 	struct osd_security_parameters *sec_parms = _osd_req_sec_params(or);
 	int ret;
···
 		or->out.last_seg = NULL;
 
 		/* they are now all chained to request sign them all together */
-		osd_sec_sign_data(&or->out_data_integ, or->out.req->bio,
+		osd_sec_sign_data(&or->out_data_integ, out_data_bio,
 				  cap_key);
 	}
 
···
 {
 	struct osd_cdb_head *cdbh = osd_cdb_head(&or->cdb);
 	bool has_in, has_out;
+	 /* Save for data_integrity without the cdb_continuation */
+	struct bio *out_data_bio = or->out.bio;
 	u64 out_data_bytes = or->out.total_bytes;
 	int ret;
 
···
 	osd_set_caps(&or->cdb, cap);
 
 	has_in = or->in.bio || or->get_attr.total_bytes;
-	has_out = or->out.bio || or->set_attr.total_bytes ||
-		or->enc_get_attr.total_bytes;
+	has_out = or->out.bio || or->cdb_cont.total_bytes ||
+		or->set_attr.total_bytes || or->enc_get_attr.total_bytes;
 
+	ret = _osd_req_finalize_cdb_cont(or, cap_key);
+	if (ret) {
+		OSD_DEBUG("_osd_req_finalize_cdb_cont failed\n");
+		return ret;
+	}
 	ret = _init_blk_request(or, has_in, has_out);
 	if (ret) {
 		OSD_DEBUG("_init_blk_request failed\n");
···
 	}
 
 	ret = _osd_req_finalize_data_integrity(or, has_in, has_out,
-					       out_data_bytes, cap_key);
+					       out_data_bio, out_data_bytes,
+					       cap_key);
 	if (ret)
 		return ret;
 

include/scsi/osd_initiator.h

···
 		void *buff;
 		unsigned alloc_size; /* 0 here means: don't call kfree */
 		unsigned total_bytes;
-	} set_attr, enc_get_attr, get_attr;
+	} cdb_cont, set_attr, enc_get_attr, get_attr;
 
 	struct _osd_io_info {
 		struct bio *bio;
···
 int osd_req_read_kern(struct osd_request *or,
 	const struct osd_obj_id *obj, u64 offset, void *buff, u64 len);
 
+/* Scatter/Gather write/read commands */
+int osd_req_write_sg(struct osd_request *or,
+	const struct osd_obj_id *obj, struct bio *bio,
+	const struct osd_sg_entry *sglist, unsigned numentries);
+int osd_req_read_sg(struct osd_request *or,
+	const struct osd_obj_id *obj, struct bio *bio,
+	const struct osd_sg_entry *sglist, unsigned numentries);
 /*
  * Root/Partition/Collection/Object Attributes commands
  */

include/scsi/osd_protocol.h

···
 	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__ */

include/scsi/osd_types.h

···
 	void *val_ptr;		/* in network order */
 };
 
+struct osd_sg_entry {
+	u64 offset;
+	u64 len;
+};
+
 #endif /* ndef __OSD_TYPES_H__ */