[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, 31 insertions, 2 deletions

diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index e1fb3d0927b0..a9a9e869188d 100644
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -78,6 +78,9 @@ enum {
 #define ISCSI_ADDRESS_BUF_LEN           64
 
 enum {
+        /* this is the maximum possible storage for AHSs */
+        ISCSI_MAX_AHS_SIZE = sizeof(struct iscsi_ecdb_ahdr) +
+                                sizeof(struct iscsi_rlength_ahdr),
         ISCSI_DIGEST_SIZE = sizeof(__u32),
 };
 
@@ -102,10 +105,13 @@ enum {
 
 struct iscsi_cmd_task {
         /*
-         * Becuae LLDs allocate their hdr differently, this is a pointer to
-         * that storage. It must be setup at session creation time.
+         * Because LLDs allocate their hdr differently, this is a pointer
+         * and length to that storage. It must be setup at session
+         * creation time.
          */
         struct iscsi_cmd        *hdr;
+        unsigned short          hdr_max;
+        unsigned short          hdr_len;        /* accumulated size of hdr used */
         int                     itt;            /* this ITT */
 
         uint32_t                unsol_datasn;
@@ -124,6 +130,11 @@ struct iscsi_cmd_task {
         void                    *dd_data;       /* driver/transport data */
 };
 
+static inline void* iscsi_next_hdr(struct iscsi_cmd_task *ctask)
+{
+        return (void*)ctask->hdr + ctask->hdr_len;
+}
+
 struct iscsi_conn {
         struct iscsi_cls_conn   *cls_conn;      /* ptr to class connection */
         void                    *dd_data;       /* iscsi_transport data */
@@ -342,4 +353,22 @@ extern void iscsi_requeue_ctask(struct iscsi_cmd_task *ctask);
 extern void iscsi_pool_free(struct iscsi_queue *, void **);
 extern int iscsi_pool_init(struct iscsi_queue *, int, void ***, int);
 
+/*
+ * inline functions to deal with padding.
+ */
+static inline unsigned int
+iscsi_padded(unsigned int len)
+{
+        return (len + ISCSI_PAD_LEN - 1) & ~(ISCSI_PAD_LEN - 1);
+}
+
+static inline unsigned int
+iscsi_padding(unsigned int len)
+{
+        len &= (ISCSI_PAD_LEN - 1);
+        if (len)
+                len = ISCSI_PAD_LEN - len;
+        return len;
+}
+
 #endif