[SCSI] iscsi_tcp, libiscsi: initial AHS Support

  at libiscsi generic code
  - currently code assumes a storage space of pdu header is allocated
    at llds ctask and is pointed to by iscsi_cmd_task->hdr. Here I add
    a hdr_max field pertaining to that storage, and an hdr_len that
    accumulates the current use of the pdu-header.

  - Add an iscsi_next_hdr() inline which returns the next free space
    to write new Header at. Also iscsi_next_hdr() is used to retrieve
    the address at which to write the header-digest.

  - Add iscsi_add_hdr(length). What the user do is calls iscsi_next_hdr()
    for address of the new header, than calls iscsi_add_hdr(length) with
    the size of the new header. iscsi_add_hdr() will check if space is
    available and update to the new size. length must be padded according
    to standard.

  - Add 2 padding inline helpers thanks to Olaf. Current patch does not
    use them but Following patches will.
    Also moved definition of ISCSI_PAD_LEN to iscsi_proto.h which had
    PAD_WORD_LEN that was never used anywhere.

  - Let iscsi_prep_scsi_cmd_pdu() signal an Error return since now  it is
    possible that it will fail.

  - I was tired of yet again writing a "this is a digest" comment next to
    sizeof(__u32) so I defined a new ISCSI_DIGEST_SIZE. Now I don't need
    any comments. Changed all places that used sizeof(__u32) or "4" in
    connection to a digest.

  iscsi_tcp specific code
  - At struct iscsi_tcp_cmd_task allocate maximum space allowed in
    standard for all headers following the iscsi_cmd header. and mark
    it so in iscsi_tcp_session_create()
  - At iscsi_send_cmd_hdr() retrieve the correct headers size and
    write header digest at iscsi_next_hdr().

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Olaf Kirch <olaf.kirch@oracle.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/scsi/iscsi_tcp.h b/drivers/scsi/iscsi_tcp.h
index f1c5411..eb3784f 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -41,7 +41,6 @@
 #define XMSTATE_IMM_HDR_INIT		0x1000
 #define XMSTATE_SOL_HDR_INIT		0x2000
 
-#define ISCSI_PAD_LEN			4
 #define ISCSI_SG_TABLESIZE		SG_ALL
 #define ISCSI_TCP_MAX_CMD_LEN		16
 
@@ -130,14 +129,14 @@ struct iscsi_buf {
 
 struct iscsi_data_task {
 	struct iscsi_data	hdr;			/* PDU */
-	char			hdrext[sizeof(__u32)];	/* Header-Digest */
+	char			hdrext[ISCSI_DIGEST_SIZE];/* Header-Digest */
 	struct iscsi_buf	digestbuf;		/* digest buffer */
 	uint32_t		digest;			/* data digest */
 };
 
 struct iscsi_tcp_mgmt_task {
 	struct iscsi_hdr	hdr;
-	char			hdrext[sizeof(__u32)]; /* Header-Digest */
+	char			hdrext[ISCSI_DIGEST_SIZE]; /* Header-Digest */
 	int			xmstate;	/* mgmt xmit progress */
 	struct iscsi_buf	headbuf;	/* header buffer */
 	struct iscsi_buf	sendbuf;	/* in progress buffer */
@@ -159,9 +158,11 @@ struct iscsi_r2t_info {
 };
 
 struct iscsi_tcp_cmd_task {
-	struct iscsi_cmd	hdr;
-	char			hdrext[4*sizeof(__u16)+	/* AHS */
-				    sizeof(__u32)];	/* HeaderDigest */
+	struct iscsi_hdr_buff {
+		struct iscsi_cmd	cmd_hdr;
+		char			hdrextbuf[ISCSI_MAX_AHS_SIZE +
+		                                  ISCSI_DIGEST_SIZE];
+	} hdr;
 	char			pad[ISCSI_PAD_LEN];
 	int			pad_count;		/* padded bytes */
 	struct iscsi_buf	headbuf;		/* header buf (xmit) */