1 files changed, 892 insertions, 1183 deletions

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 57ce2251abc8..e5be5fd4ef58 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -48,7 +48,7 @@ MODULE_AUTHOR("Dmitry Yusupov <dmitry_yus@yahoo.com>, "
               "Alex Aizman <itn780@yahoo.com>");
 MODULE_DESCRIPTION("iSCSI/TCP data-path");
 MODULE_LICENSE("GPL");
-/* #define DEBUG_TCP */
+#undef DEBUG_TCP
 #define DEBUG_ASSERT
 
 #ifdef DEBUG_TCP
@@ -67,115 +67,429 @@ MODULE_LICENSE("GPL");
 static unsigned int iscsi_max_lun = 512;
 module_param_named(max_lun, iscsi_max_lun, uint, S_IRUGO);
 
+static int iscsi_tcp_hdr_recv_done(struct iscsi_tcp_conn *tcp_conn,
+                                   struct iscsi_segment *segment);
+
+/*
+ * Scatterlist handling: inside the iscsi_segment, we
+ * remember an index into the scatterlist, and set data/size
+ * to the current scatterlist entry. For highmem pages, we
+ * kmap as needed.
+ *
+ * Note that the page is unmapped when we return from
+ * TCP's data_ready handler, so we may end up mapping and
+ * unmapping the same page repeatedly. The whole reason
+ * for this is that we shouldn't keep the page mapped
+ * outside the softirq.
+ */
+
+/**
+ * iscsi_tcp_segment_init_sg - init indicated scatterlist entry
+ * @segment: the buffer object
+ * @sg: scatterlist
+ * @offset: byte offset into that sg entry
+ *
+ * This function sets up the segment so that subsequent
+ * data is copied to the indicated sg entry, at the given
+ * offset.
+ */
 static inline void
-iscsi_buf_init_iov(struct iscsi_buf *ibuf, char *vbuf, int size)
+iscsi_tcp_segment_init_sg(struct iscsi_segment *segment,
+                          struct scatterlist *sg, unsigned int offset)
 {
-        sg_init_one(&ibuf->sg, vbuf, size);
-        ibuf->sent = 0;
-        ibuf->use_sendmsg = 1;
+        segment->sg = sg;
+        segment->sg_offset = offset;
+        segment->size = min(sg->length - offset,
+                            segment->total_size - segment->total_copied);
+        segment->data = NULL;
 }
 
+/**
+ * iscsi_tcp_segment_map - map the current S/G page
+ * @segment: iscsi_segment
+ * @recv: 1 if called from recv path
+ *
+ * We only need to possibly kmap data if scatter lists are being used,
+ * because the iscsi passthrough and internal IO paths will never use high
+ * mem pages.
+ */
 static inline void
-iscsi_buf_init_sg(struct iscsi_buf *ibuf, struct scatterlist *sg)
+iscsi_tcp_segment_map(struct iscsi_segment *segment, int recv)
 {
-        sg_init_table(&ibuf->sg, 1);
-        sg_set_page(&ibuf->sg, sg_page(sg), sg->length, sg->offset);
+        struct scatterlist *sg;
+
+        if (segment->data != NULL || !segment->sg)
+                return;
+
+        sg = segment->sg;
+        BUG_ON(segment->sg_mapped);
+        BUG_ON(sg->length == 0);
+
         /*
-         * Fastpath: sg element fits into single page
+         * If the page count is greater than one it is ok to send
+         * to the network layer's zero copy send path. If not we
+         * have to go the slow sendmsg path. We always map for the
+         * recv path.
          */
-        if (sg->length + sg->offset <= PAGE_SIZE && !PageSlab(sg_page(sg)))
-                ibuf->use_sendmsg = 0;
-        else
-                ibuf->use_sendmsg = 1;
-        ibuf->sent = 0;
+        if (page_count(sg_page(sg)) >= 1 && !recv)
+                return;
+
+        debug_tcp("iscsi_tcp_segment_map %s %p\n", recv ? "recv" : "xmit",
+                  segment);
+        segment->sg_mapped = kmap_atomic(sg_page(sg), KM_SOFTIRQ0);
+        segment->data = segment->sg_mapped + sg->offset + segment->sg_offset;
 }
 
-static inline int
-iscsi_buf_left(struct iscsi_buf *ibuf)
+static inline void
+iscsi_tcp_segment_unmap(struct iscsi_segment *segment)
 {
-        int rc;
+        debug_tcp("iscsi_tcp_segment_unmap %p\n", segment);
 
-        rc = ibuf->sg.length - ibuf->sent;
-        BUG_ON(rc < 0);
-        return rc;
+        if (segment->sg_mapped) {
+                debug_tcp("iscsi_tcp_segment_unmap valid\n");
+                kunmap_atomic(segment->sg_mapped, KM_SOFTIRQ0);
+                segment->sg_mapped = NULL;
+                segment->data = NULL;
+        }
 }
 
+/*
+ * Splice the digest buffer into the buffer
+ */
 static inline void
-iscsi_hdr_digest(struct iscsi_conn *conn, struct iscsi_buf *buf,
-                 u8* crc)
+iscsi_tcp_segment_splice_digest(struct iscsi_segment *segment, void *digest)
 {
-        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-
-        crypto_hash_digest(&tcp_conn->tx_hash, &buf->sg, buf->sg.length, crc);
-        buf->sg.length += sizeof(u32);
+        segment->data = digest;
+        segment->digest_len = ISCSI_DIGEST_SIZE;
+        segment->total_size += ISCSI_DIGEST_SIZE;
+        segment->size = ISCSI_DIGEST_SIZE;
+        segment->copied = 0;
+        segment->sg = NULL;
+        segment->hash = NULL;
 }
 
+/**
+ * iscsi_tcp_segment_done - check whether the segment is complete
+ * @segment: iscsi segment to check
+ * @recv: set to one of this is called from the recv path
+ * @copied: number of bytes copied
+ *
+ * Check if we're done receiving this segment. If the receive
+ * buffer is full but we expect more data, move on to the
+ * next entry in the scatterlist.
+ *
+ * If the amount of data we received isn't a multiple of 4,
+ * we will transparently receive the pad bytes, too.
+ *
+ * This function must be re-entrant.
+ */
 static inline int
-iscsi_hdr_extract(struct iscsi_tcp_conn *tcp_conn)
+iscsi_tcp_segment_done(struct iscsi_segment *segment, int recv, unsigned copied)
 {
-        struct sk_buff *skb = tcp_conn->in.skb;
-
-        tcp_conn->in.zero_copy_hdr = 0;
+        static unsigned char padbuf[ISCSI_PAD_LEN];
+        struct scatterlist sg;
+        unsigned int pad;
 
-        if (tcp_conn->in.copy >= tcp_conn->hdr_size &&
-            tcp_conn->in_progress == IN_PROGRESS_WAIT_HEADER) {
+        debug_tcp("copied %u %u size %u %s\n", segment->copied, copied,
+                  segment->size, recv ? "recv" : "xmit");
+        if (segment->hash && copied) {
                 /*
-                 * Zero-copy PDU Header: using connection context
-                 * to store header pointer.
+                 * If a segment is kmapd we must unmap it before sending
+                 * to the crypto layer since that will try to kmap it again.
                  */
-                if (skb_shinfo(skb)->frag_list == NULL &&
-                    !skb_shinfo(skb)->nr_frags) {
-                        tcp_conn->in.hdr = (struct iscsi_hdr *)
-                                ((char*)skb->data + tcp_conn->in.offset);
-                        tcp_conn->in.zero_copy_hdr = 1;
+                iscsi_tcp_segment_unmap(segment);
+
+                if (!segment->data) {
+                        sg_init_table(&sg, 1);
+                        sg_set_page(&sg, sg_page(segment->sg), copied,
+                                    segment->copied + segment->sg_offset +
+                                                        segment->sg->offset);
+                } else
+                        sg_init_one(&sg, segment->data + segment->copied,
+                                    copied);
+                crypto_hash_update(segment->hash, &sg, copied);
+        }
+
+        segment->copied += copied;
+        if (segment->copied < segment->size) {
+                iscsi_tcp_segment_map(segment, recv);
+                return 0;
+        }
+
+        segment->total_copied += segment->copied;
+        segment->copied = 0;
+        segment->size = 0;
+
+        /* Unmap the current scatterlist page, if there is one. */
+        iscsi_tcp_segment_unmap(segment);
+
+        /* Do we have more scatterlist entries? */
+        debug_tcp("total copied %u total size %u\n", segment->total_copied,
+                   segment->total_size);
+        if (segment->total_copied < segment->total_size) {
+                /* Proceed to the next entry in the scatterlist. */
+                iscsi_tcp_segment_init_sg(segment, sg_next(segment->sg),
+                                          0);
+                iscsi_tcp_segment_map(segment, recv);
+                BUG_ON(segment->size == 0);
+                return 0;
+        }
+
+        /* Do we need to handle padding? */
+        pad = iscsi_padding(segment->total_copied);
+        if (pad != 0) {
+                debug_tcp("consume %d pad bytes\n", pad);
+                segment->total_size += pad;
+                segment->size = pad;
+                segment->data = padbuf;
+                return 0;
+        }
+
+        /*
+         * Set us up for transferring the data digest. hdr digest
+         * is completely handled in hdr done function.
+         */
+        if (segment->hash) {
+                crypto_hash_final(segment->hash, segment->digest);
+                iscsi_tcp_segment_splice_digest(segment,
+                                 recv ? segment->recv_digest : segment->digest);
+                return 0;
+        }
+
+        return 1;
+}
+
+/**
+ * iscsi_tcp_xmit_segment - transmit segment
+ * @tcp_conn: the iSCSI TCP connection
+ * @segment: the buffer to transmnit
+ *
+ * This function transmits as much of the buffer as
+ * the network layer will accept, and returns the number of
+ * bytes transmitted.
+ *
+ * If CRC hashing is enabled, the function will compute the
+ * hash as it goes. When the entire segment has been transmitted,
+ * it will retrieve the hash value and send it as well.
+ */
+static int
+iscsi_tcp_xmit_segment(struct iscsi_tcp_conn *tcp_conn,
+                       struct iscsi_segment *segment)
+{
+        struct socket *sk = tcp_conn->sock;
+        unsigned int copied = 0;
+        int r = 0;
+
+        while (!iscsi_tcp_segment_done(segment, 0, r)) {
+                struct scatterlist *sg;
+                unsigned int offset, copy;
+                int flags = 0;
+
+                r = 0;
+                offset = segment->copied;
+                copy = segment->size - offset;
+
+                if (segment->total_copied + segment->size < segment->total_size)
+                        flags |= MSG_MORE;
+
+                /* Use sendpage if we can; else fall back to sendmsg */
+                if (!segment->data) {
+                        sg = segment->sg;
+                        offset += segment->sg_offset + sg->offset;
+                        r = tcp_conn->sendpage(sk, sg_page(sg), offset, copy,
+                                               flags);
                 } else {
-                        /* ignoring return code since we checked
-                         * in.copy before */
-                        skb_copy_bits(skb, tcp_conn->in.offset,
-                                &tcp_conn->hdr, tcp_conn->hdr_size);
-                        tcp_conn->in.hdr = &tcp_conn->hdr;
+                        struct msghdr msg = { .msg_flags = flags };
+                        struct kvec iov = {
+                                .iov_base = segment->data + offset,
+                                .iov_len = copy
+                        };
+
+                        r = kernel_sendmsg(sk, &msg, &iov, 1, copy);
                 }
-                tcp_conn->in.offset += tcp_conn->hdr_size;
-                tcp_conn->in.copy -= tcp_conn->hdr_size;
-        } else {
-                int hdr_remains;
-                int copylen;
 
-                /*
-                 * PDU header scattered across SKB's,
-                 * copying it... This'll happen quite rarely.
-                 */
+                if (r < 0) {
+                        iscsi_tcp_segment_unmap(segment);
+                        if (copied || r == -EAGAIN)
+                                break;
+                        return r;
+                }
+                copied += r;
+        }
+        return copied;
+}
+
+/**
+ * iscsi_tcp_segment_recv - copy data to segment
+ * @tcp_conn: the iSCSI TCP connection
+ * @segment: the buffer to copy to
+ * @ptr: data pointer
+ * @len: amount of data available
+ *
+ * This function copies up to @len bytes to the
+ * given buffer, and returns the number of bytes
+ * consumed, which can actually be less than @len.
+ *
+ * If hash digest is enabled, the function will update the
+ * hash while copying.
+ * Combining these two operations doesn't buy us a lot (yet),
+ * but in the future we could implement combined copy+crc,
+ * just way we do for network layer checksums.
+ */
+static int
+iscsi_tcp_segment_recv(struct iscsi_tcp_conn *tcp_conn,
+                       struct iscsi_segment *segment, const void *ptr,
+                       unsigned int len)
+{
+        unsigned int copy = 0, copied = 0;
+
+        while (!iscsi_tcp_segment_done(segment, 1, copy)) {
+                if (copied == len) {
+                        debug_tcp("iscsi_tcp_segment_recv copied %d bytes\n",
+                                  len);
+                        break;
+                }
+
+                copy = min(len - copied, segment->size - segment->copied);
+                debug_tcp("iscsi_tcp_segment_recv copying %d\n", copy);
+                memcpy(segment->data + segment->copied, ptr + copied, copy);
+                copied += copy;
+        }
+        return copied;
+}
 
-                if (tcp_conn->in_progress == IN_PROGRESS_WAIT_HEADER)
-                        tcp_conn->in.hdr_offset = 0;
+static inline void
+iscsi_tcp_dgst_header(struct hash_desc *hash, const void *hdr, size_t hdrlen,
+                      unsigned char digest[ISCSI_DIGEST_SIZE])
+{
+        struct scatterlist sg;
 
-                hdr_remains = tcp_conn->hdr_size - tcp_conn->in.hdr_offset;
-                BUG_ON(hdr_remains <= 0);
+        sg_init_one(&sg, hdr, hdrlen);
+        crypto_hash_digest(hash, &sg, hdrlen, digest);
+}
 
-                copylen = min(tcp_conn->in.copy, hdr_remains);
-                skb_copy_bits(skb, tcp_conn->in.offset,
-                        (char*)&tcp_conn->hdr + tcp_conn->in.hdr_offset,
-                        copylen);
+static inline int
+iscsi_tcp_dgst_verify(struct iscsi_tcp_conn *tcp_conn,
+                      struct iscsi_segment *segment)
+{
+        if (!segment->digest_len)
+                return 1;
 
-                debug_tcp("PDU gather offset %d bytes %d in.offset %d "
-                       "in.copy %d\n", tcp_conn->in.hdr_offset, copylen,
-                       tcp_conn->in.offset, tcp_conn->in.copy);
+        if (memcmp(segment->recv_digest, segment->digest,
+                   segment->digest_len)) {
+                debug_scsi("digest mismatch\n");
+                return 0;
+        }
 
-                tcp_conn->in.offset += copylen;
-                tcp_conn->in.copy -= copylen;
-                if (copylen < hdr_remains)  {
-                        tcp_conn->in_progress = IN_PROGRESS_HEADER_GATHER;
-                        tcp_conn->in.hdr_offset += copylen;
-                        return -EAGAIN;
+        return 1;
+}
+
+/*
+ * Helper function to set up segment buffer
+ */
+static inline void
+__iscsi_segment_init(struct iscsi_segment *segment, size_t size,
+                     iscsi_segment_done_fn_t *done, struct hash_desc *hash)
+{
+        memset(segment, 0, sizeof(*segment));
+        segment->total_size = size;
+        segment->done = done;
+
+        if (hash) {
+                segment->hash = hash;
+                crypto_hash_init(hash);
+        }
+}
+
+static inline void
+iscsi_segment_init_linear(struct iscsi_segment *segment, void *data,
+                          size_t size, iscsi_segment_done_fn_t *done,
+                          struct hash_desc *hash)
+{
+        __iscsi_segment_init(segment, size, done, hash);
+        segment->data = data;
+        segment->size = size;
+}
+
+static inline int
+iscsi_segment_seek_sg(struct iscsi_segment *segment,
+                      struct scatterlist *sg_list, unsigned int sg_count,
+                      unsigned int offset, size_t size,
+                      iscsi_segment_done_fn_t *done, struct hash_desc *hash)
+{
+        struct scatterlist *sg;
+        unsigned int i;
+
+        debug_scsi("iscsi_segment_seek_sg offset %u size %llu\n",
+                  offset, size);
+        __iscsi_segment_init(segment, size, done, hash);
+        for_each_sg(sg_list, sg, sg_count, i) {
+                debug_scsi("sg %d, len %u offset %u\n", i, sg->length,
+                           sg->offset);
+                if (offset < sg->length) {
+                        iscsi_tcp_segment_init_sg(segment, sg, offset);
+                        return 0;
                 }
-                tcp_conn->in.hdr = &tcp_conn->hdr;
-                tcp_conn->discontiguous_hdr_cnt++;
-                tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
+                offset -= sg->length;
         }
 
+        return ISCSI_ERR_DATA_OFFSET;
+}
+
+/**
+ * iscsi_tcp_hdr_recv_prep - prep segment for hdr reception
+ * @tcp_conn: iscsi connection to prep for
+ *
+ * This function always passes NULL for the hash argument, because when this
+ * function is called we do not yet know the final size of the header and want
+ * to delay the digest processing until we know that.
+ */
+static void
+iscsi_tcp_hdr_recv_prep(struct iscsi_tcp_conn *tcp_conn)
+{
+        debug_tcp("iscsi_tcp_hdr_recv_prep(%p%s)\n", tcp_conn,
+                  tcp_conn->iscsi_conn->hdrdgst_en ? ", digest enabled" : "");
+        iscsi_segment_init_linear(&tcp_conn->in.segment,
+                                tcp_conn->in.hdr_buf, sizeof(struct iscsi_hdr),
+                                iscsi_tcp_hdr_recv_done, NULL);
+}
+
+/*
+ * Handle incoming reply to any other type of command
+ */
+static int
+iscsi_tcp_data_recv_done(struct iscsi_tcp_conn *tcp_conn,
+                         struct iscsi_segment *segment)
+{
+        struct iscsi_conn *conn = tcp_conn->iscsi_conn;
+        int rc = 0;
+
+        if (!iscsi_tcp_dgst_verify(tcp_conn, segment))
+                return ISCSI_ERR_DATA_DGST;
+
+        rc = iscsi_complete_pdu(conn, tcp_conn->in.hdr,
+                        conn->data, tcp_conn->in.datalen);
+        if (rc)
+                return rc;
+
+        iscsi_tcp_hdr_recv_prep(tcp_conn);
         return 0;
 }
 
+static void
+iscsi_tcp_data_recv_prep(struct iscsi_tcp_conn *tcp_conn)
+{
+        struct iscsi_conn *conn = tcp_conn->iscsi_conn;
+        struct hash_desc *rx_hash = NULL;
+
+        if (conn->datadgst_en)
+                rx_hash = &tcp_conn->rx_hash;
+
+        iscsi_segment_init_linear(&tcp_conn->in.segment,
+                                conn->data, tcp_conn->in.datalen,
+                                iscsi_tcp_data_recv_done, rx_hash);
+}
+
 /*
  * must be called with session lock
  */
@@ -184,7 +498,6 @@ iscsi_tcp_cleanup_ctask(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
 {
         struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
         struct iscsi_r2t_info *r2t;
-        struct scsi_cmnd *sc;
 
         /* flush ctask's r2t queues */
         while (__kfifo_get(tcp_ctask->r2tqueue, (void*)&r2t, sizeof(void*))) {
@@ -193,12 +506,12 @@ iscsi_tcp_cleanup_ctask(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
                 debug_scsi("iscsi_tcp_cleanup_ctask pending r2t dropped\n");
         }
 
-        sc = ctask->sc;
-        if (unlikely(!sc))
-                return;
-
-        tcp_ctask->xmstate = XMSTATE_VALUE_IDLE;
-        tcp_ctask->r2t = NULL;
+        r2t = tcp_ctask->r2t;
+        if (r2t != NULL) {
+                __kfifo_put(tcp_ctask->r2tpool.queue, (void*)&r2t,
+                            sizeof(void*));
+                tcp_ctask->r2t = NULL;
+        }
 }
 
 /**
@@ -217,11 +530,6 @@ iscsi_data_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         int datasn = be32_to_cpu(rhdr->datasn);
 
         iscsi_update_cmdsn(session, (struct iscsi_nopin*)rhdr);
-        /*
-         * setup Data-In byte counter (gets decremented..)
-         */
-        ctask->data_count = tcp_conn->in.datalen;
-
         if (tcp_conn->in.datalen == 0)
                 return 0;
 
@@ -242,22 +550,20 @@ iscsi_data_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         }
 
         if (rhdr->flags & ISCSI_FLAG_DATA_STATUS) {
+                sc->result = (DID_OK << 16) | rhdr->cmd_status;
                 conn->exp_statsn = be32_to_cpu(rhdr->statsn) + 1;
-                if (rhdr->flags & ISCSI_FLAG_DATA_UNDERFLOW) {
+                if (rhdr->flags & (ISCSI_FLAG_DATA_UNDERFLOW |
+                                   ISCSI_FLAG_DATA_OVERFLOW)) {
                         int res_count = be32_to_cpu(rhdr->residual_count);
 
                         if (res_count > 0 &&
-                            res_count <= scsi_bufflen(sc)) {
+                            (rhdr->flags & ISCSI_FLAG_CMD_OVERFLOW ||
+                             res_count <= scsi_bufflen(sc)))
                                 scsi_set_resid(sc, res_count);
-                                sc->result = (DID_OK << 16) | rhdr->cmd_status;
-                        } else
+                        else
                                 sc->result = (DID_BAD_TARGET << 16) |
                                         rhdr->cmd_status;
-                } else if (rhdr->flags & ISCSI_FLAG_DATA_OVERFLOW) {
-                        scsi_set_resid(sc, be32_to_cpu(rhdr->residual_count));
-                        sc->result = (DID_OK << 16) | rhdr->cmd_status;
-                } else
-                        sc->result = (DID_OK << 16) | rhdr->cmd_status;
+                }
         }
 
         conn->datain_pdus_cnt++;
@@ -281,9 +587,6 @@ iscsi_solicit_data_init(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask,
                         struct iscsi_r2t_info *r2t)
 {
         struct iscsi_data *hdr;
-        struct scsi_cmnd *sc = ctask->sc;
-        int i, sg_count = 0;
-        struct scatterlist *sg;
 
         hdr = &r2t->dtask.hdr;
         memset(hdr, 0, sizeof(struct iscsi_data));
@@ -307,34 +610,6 @@ iscsi_solicit_data_init(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask,
         conn->dataout_pdus_cnt++;
 
         r2t->sent = 0;
-
-        iscsi_buf_init_iov(&r2t->headbuf, (char*)hdr,
-                           sizeof(struct iscsi_hdr));
-
-        sg = scsi_sglist(sc);
-        r2t->sg = NULL;
-        for (i = 0; i < scsi_sg_count(sc); i++, sg += 1) {
-                /* FIXME: prefetch ? */
-                if (sg_count + sg->length > r2t->data_offset) {
-                        int page_offset;
-
-                        /* sg page found! */
-
-                        /* offset within this page */
-                        page_offset = r2t->data_offset - sg_count;
-
-                        /* fill in this buffer */
-                        iscsi_buf_init_sg(&r2t->sendbuf, sg);
-                        r2t->sendbuf.sg.offset += page_offset;
-                        r2t->sendbuf.sg.length -= page_offset;
-
-                        /* xmit logic will continue with next one */
-                        r2t->sg = sg + 1;
-                        break;
-                }
-                sg_count += sg->length;
-        }
-        BUG_ON(r2t->sg == NULL);
 }
 
 /**
@@ -366,14 +641,11 @@ iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         }
 
         /* fill-in new R2T associated with the task */
-        spin_lock(&session->lock);
         iscsi_update_cmdsn(session, (struct iscsi_nopin*)rhdr);
 
-        if (!ctask->sc || ctask->mtask ||
-             session->state != ISCSI_STATE_LOGGED_IN) {
+        if (!ctask->sc || session->state != ISCSI_STATE_LOGGED_IN) {
                 printk(KERN_INFO "iscsi_tcp: dropping R2T itt %d in "
                        "recovery...\n", ctask->itt);
-                spin_unlock(&session->lock);
                 return 0;
         }
 
@@ -384,7 +656,8 @@ iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         r2t->data_length = be32_to_cpu(rhdr->data_length);
         if (r2t->data_length == 0) {
                 printk(KERN_ERR "iscsi_tcp: invalid R2T with zero data len\n");
-                spin_unlock(&session->lock);
+                __kfifo_put(tcp_ctask->r2tpool.queue, (void*)&r2t,
+                            sizeof(void*));
                 return ISCSI_ERR_DATALEN;
         }
 
@@ -395,10 +668,11 @@ iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
 
         r2t->data_offset = be32_to_cpu(rhdr->data_offset);
         if (r2t->data_offset + r2t->data_length > scsi_bufflen(ctask->sc)) {
-                spin_unlock(&session->lock);
                 printk(KERN_ERR "iscsi_tcp: invalid R2T with data len %u at "
                        "offset %u and total length %d\n", r2t->data_length,
                        r2t->data_offset, scsi_bufflen(ctask->sc));
+                __kfifo_put(tcp_ctask->r2tpool.queue, (void*)&r2t,
+                            sizeof(void*));
                 return ISCSI_ERR_DATALEN;
         }
 
@@ -409,26 +683,55 @@ iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
 
         tcp_ctask->exp_datasn = r2tsn + 1;
         __kfifo_put(tcp_ctask->r2tqueue, (void*)&r2t, sizeof(void*));
-        set_bit(XMSTATE_BIT_SOL_HDR_INIT, &tcp_ctask->xmstate);
-        list_move_tail(&ctask->running, &conn->xmitqueue);
-
-        scsi_queue_work(session->host, &conn->xmitwork);
         conn->r2t_pdus_cnt++;
-        spin_unlock(&session->lock);
 
+        iscsi_requeue_ctask(ctask);
         return 0;
 }
 
+/*
+ * Handle incoming reply to DataIn command
+ */
 static int
-iscsi_tcp_hdr_recv(struct iscsi_conn *conn)
+iscsi_tcp_process_data_in(struct iscsi_tcp_conn *tcp_conn,
+                          struct iscsi_segment *segment)
+{
+        struct iscsi_conn *conn = tcp_conn->iscsi_conn;
+        struct iscsi_hdr *hdr = tcp_conn->in.hdr;
+        int rc;
+
+        if (!iscsi_tcp_dgst_verify(tcp_conn, segment))
+                return ISCSI_ERR_DATA_DGST;
+
+        /* check for non-exceptional status */
+        if (hdr->flags & ISCSI_FLAG_DATA_STATUS) {
+                rc = iscsi_complete_pdu(conn, tcp_conn->in.hdr, NULL, 0);
+                if (rc)
+                        return rc;
+        }
+
+        iscsi_tcp_hdr_recv_prep(tcp_conn);
+        return 0;
+}
+
+/**
+ * iscsi_tcp_hdr_dissect - process PDU header
+ * @conn: iSCSI connection
+ * @hdr: PDU header
+ *
+ * This function analyzes the header of the PDU received,
+ * and performs several sanity checks. If the PDU is accompanied
+ * by data, the receive buffer is set up to copy the incoming data
+ * to the correct location.
+ */
+static int
+iscsi_tcp_hdr_dissect(struct iscsi_conn *conn, struct iscsi_hdr *hdr)
 {
         int rc = 0, opcode, ahslen;
-        struct iscsi_hdr *hdr;
         struct iscsi_session *session = conn->session;
         struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-        uint32_t cdgst, rdgst = 0, itt;
-
-        hdr = tcp_conn->in.hdr;
+        struct iscsi_cmd_task *ctask;
+        uint32_t itt;
 
         /* verify PDU length */
         tcp_conn->in.datalen = ntoh24(hdr->dlength);
@@ -437,78 +740,73 @@ iscsi_tcp_hdr_recv(struct iscsi_conn *conn)
                        tcp_conn->in.datalen, conn->max_recv_dlength);
                 return ISCSI_ERR_DATALEN;
         }
-        tcp_conn->data_copied = 0;
 
-        /* read AHS */
+        /* Additional header segments. So far, we don't
+         * process additional headers.
+         */
         ahslen = hdr->hlength << 2;
-        tcp_conn->in.offset += ahslen;
-        tcp_conn->in.copy -= ahslen;
-        if (tcp_conn->in.copy < 0) {
-                printk(KERN_ERR "iscsi_tcp: can't handle AHS with length "
-                       "%d bytes\n", ahslen);
-                return ISCSI_ERR_AHSLEN;
-        }
-
-        /* calculate read padding */
-        tcp_conn->in.padding = tcp_conn->in.datalen & (ISCSI_PAD_LEN-1);
-        if (tcp_conn->in.padding) {
-                tcp_conn->in.padding = ISCSI_PAD_LEN - tcp_conn->in.padding;
-                debug_scsi("read padding %d bytes\n", tcp_conn->in.padding);
-        }
-
-        if (conn->hdrdgst_en) {
-                struct scatterlist sg;
-
-                sg_init_one(&sg, (u8 *)hdr,
-                            sizeof(struct iscsi_hdr) + ahslen);
-                crypto_hash_digest(&tcp_conn->rx_hash, &sg, sg.length,
-                                   (u8 *)&cdgst);
-                rdgst = *(uint32_t*)((char*)hdr + sizeof(struct iscsi_hdr) +
-                                     ahslen);
-                if (cdgst != rdgst) {
-                        printk(KERN_ERR "iscsi_tcp: hdrdgst error "
-                               "recv 0x%x calc 0x%x\n", rdgst, cdgst);
-                        return ISCSI_ERR_HDR_DGST;
-                }
-        }
 
         opcode = hdr->opcode & ISCSI_OPCODE_MASK;
         /* verify itt (itt encoding: age+cid+itt) */
         rc = iscsi_verify_itt(conn, hdr, &itt);
-        if (rc == ISCSI_ERR_NO_SCSI_CMD) {
-                tcp_conn->in.datalen = 0; /* force drop */
-                return 0;
-        } else if (rc)
+        if (rc)
                 return rc;
 
-        debug_tcp("opcode 0x%x offset %d copy %d ahslen %d datalen %d\n",
-                  opcode, tcp_conn->in.offset, tcp_conn->in.copy,
-                  ahslen, tcp_conn->in.datalen);
+        debug_tcp("opcode 0x%x ahslen %d datalen %d\n",
+                  opcode, ahslen, tcp_conn->in.datalen);
 
         switch(opcode) {
         case ISCSI_OP_SCSI_DATA_IN:
-                tcp_conn->in.ctask = session->cmds[itt];
-                rc = iscsi_data_rsp(conn, tcp_conn->in.ctask);
+                ctask = session->cmds[itt];
+                spin_lock(&conn->session->lock);
+                rc = iscsi_data_rsp(conn, ctask);
+                spin_unlock(&conn->session->lock);
                 if (rc)
                         return rc;
+                if (tcp_conn->in.datalen) {
+                        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
+                        struct hash_desc *rx_hash = NULL;
+
+                        /*
+                         * Setup copy of Data-In into the Scsi_Cmnd
+                         * Scatterlist case:
+                         * We set up the iscsi_segment to point to the next
+                         * scatterlist entry to copy to. As we go along,
+                         * we move on to the next scatterlist entry and
+                         * update the digest per-entry.
+                         */
+                        if (conn->datadgst_en)
+                                rx_hash = &tcp_conn->rx_hash;
+
+                        debug_tcp("iscsi_tcp_begin_data_in(%p, offset=%d, "
+                                  "datalen=%d)\n", tcp_conn,
+                                  tcp_ctask->data_offset,
+                                  tcp_conn->in.datalen);
+                        return iscsi_segment_seek_sg(&tcp_conn->in.segment,
+                                                     scsi_sglist(ctask->sc),
+                                                     scsi_sg_count(ctask->sc),
+                                                     tcp_ctask->data_offset,
+                                                     tcp_conn->in.datalen,
+                                                     iscsi_tcp_process_data_in,
+                                                     rx_hash);
+                }
                 /* fall through */
         case ISCSI_OP_SCSI_CMD_RSP:
-                tcp_conn->in.ctask = session->cmds[itt];
-                if (tcp_conn->in.datalen)
-                        goto copy_hdr;
-
-                spin_lock(&session->lock);
-                rc = __iscsi_complete_pdu(conn, hdr, NULL, 0);
-                spin_unlock(&session->lock);
+                if (tcp_conn->in.datalen) {
+                        iscsi_tcp_data_recv_prep(tcp_conn);
+                        return 0;
+                }
+                rc = iscsi_complete_pdu(conn, hdr, NULL, 0);
                 break;
         case ISCSI_OP_R2T:
-                tcp_conn->in.ctask = session->cmds[itt];
+                ctask = session->cmds[itt];
                 if (ahslen)
                         rc = ISCSI_ERR_AHSLEN;
-                else if (tcp_conn->in.ctask->sc->sc_data_direction ==
-                                                                DMA_TO_DEVICE)
-                        rc = iscsi_r2t_rsp(conn, tcp_conn->in.ctask);
-                else
+                else if (ctask->sc->sc_data_direction == DMA_TO_DEVICE) {
+                        spin_lock(&session->lock);
+                        rc = iscsi_r2t_rsp(conn, ctask);
+                        spin_unlock(&session->lock);
+                } else
                         rc = ISCSI_ERR_PROTO;
                 break;
         case ISCSI_OP_LOGIN_RSP:
@@ -520,8 +818,7 @@ iscsi_tcp_hdr_recv(struct iscsi_conn *conn)
                  * than 8K, but there are no targets that currently do this.
                  * For now we fail until we find a vendor that needs it
                  */
-                if (ISCSI_DEF_MAX_RECV_SEG_LEN <
-                    tcp_conn->in.datalen) {
+                if (ISCSI_DEF_MAX_RECV_SEG_LEN < tcp_conn->in.datalen) {
                         printk(KERN_ERR "iscsi_tcp: received buffer of len %u "
                               "but conn buffer is only %u (opcode %0x)\n",
                               tcp_conn->in.datalen,
@@ -530,8 +827,13 @@ iscsi_tcp_hdr_recv(struct iscsi_conn *conn)
                         break;
                 }
 
-                if (tcp_conn->in.datalen)
-                        goto copy_hdr;
+                /* If there's data coming in with the response,
+                 * receive it to the connection's buffer.
+                 */
+                if (tcp_conn->in.datalen) {
+                        iscsi_tcp_data_recv_prep(tcp_conn);
+                        return 0;
+                }
         /* fall through */
         case ISCSI_OP_LOGOUT_RSP:
         case ISCSI_OP_NOOP_IN:
@@ -543,461 +845,161 @@ iscsi_tcp_hdr_recv(struct iscsi_conn *conn)
                 break;
         }
 
-        return rc;
-
-copy_hdr:
-        /*
-         * if we did zero copy for the header but we will need multiple
-         * skbs to complete the command then we have to copy the header
-         * for later use
-         */
-        if (tcp_conn->in.zero_copy_hdr && tcp_conn->in.copy <=
-           (tcp_conn->in.datalen + tcp_conn->in.padding +
-            (conn->datadgst_en ? 4 : 0))) {
-                debug_tcp("Copying header for later use. in.copy %d in.datalen"
-                          " %d\n", tcp_conn->in.copy, tcp_conn->in.datalen);
-                memcpy(&tcp_conn->hdr, tcp_conn->in.hdr,
-                       sizeof(struct iscsi_hdr));
-                tcp_conn->in.hdr = &tcp_conn->hdr;
-                tcp_conn->in.zero_copy_hdr = 0;
-        }
-        return 0;
-}
-
-/**
- * iscsi_ctask_copy - copy skb bits to the destanation cmd task
- * @conn: iscsi tcp connection
- * @ctask: scsi command task
- * @buf: buffer to copy to
- * @buf_size: size of buffer
- * @offset: offset within the buffer
- *
- * Notes:
- *      The function calls skb_copy_bits() and updates per-connection and
- *      per-cmd byte counters.
- *
- *      Read counters (in bytes):
- *
- *      conn->in.offset         offset within in progress SKB
- *      conn->in.copy           left to copy from in progress SKB
- *                              including padding
- *      conn->in.copied         copied already from in progress SKB
- *      conn->data_copied       copied already from in progress buffer
- *      ctask->sent             total bytes sent up to the MidLayer
- *      ctask->data_count       left to copy from in progress Data-In
- *      buf_left                left to copy from in progress buffer
- **/
-static inline int
-iscsi_ctask_copy(struct iscsi_tcp_conn *tcp_conn, struct iscsi_cmd_task *ctask,
-                void *buf, int buf_size, int offset)
-{
-        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
-        int buf_left = buf_size - (tcp_conn->data_copied + offset);
-        unsigned size = min(tcp_conn->in.copy, buf_left);
-        int rc;
-
-        size = min(size, ctask->data_count);
-
-        debug_tcp("ctask_copy %d bytes at offset %d copied %d\n",
-               size, tcp_conn->in.offset, tcp_conn->in.copied);
-
-        BUG_ON(size <= 0);
-        BUG_ON(tcp_ctask->sent + size > scsi_bufflen(ctask->sc));
-
-        rc = skb_copy_bits(tcp_conn->in.skb, tcp_conn->in.offset,
-                           (char*)buf + (offset + tcp_conn->data_copied), size);
-        /* must fit into skb->len */
-        BUG_ON(rc);
-
-        tcp_conn->in.offset += size;
-        tcp_conn->in.copy -= size;
-        tcp_conn->in.copied += size;
-        tcp_conn->data_copied += size;
-        tcp_ctask->sent += size;
-        ctask->data_count -= size;
-
-        BUG_ON(tcp_conn->in.copy < 0);
-        BUG_ON(ctask->data_count < 0);
-
-        if (buf_size != (tcp_conn->data_copied + offset)) {
-                if (!ctask->data_count) {
-                        BUG_ON(buf_size - tcp_conn->data_copied < 0);
-                        /* done with this PDU */
-                        return buf_size - tcp_conn->data_copied;
-                }
-                return -EAGAIN;
+        if (rc == 0) {
+                /* Anything that comes with data should have
+                 * been handled above. */
+                if (tcp_conn->in.datalen)
+                        return ISCSI_ERR_PROTO;
+                iscsi_tcp_hdr_recv_prep(tcp_conn);
         }
 
-        /* done with this buffer or with both - PDU and buffer */
-        tcp_conn->data_copied = 0;
-        return 0;
+        return rc;
 }
 
 /**
- * iscsi_tcp_copy - copy skb bits to the destanation buffer
- * @conn: iscsi tcp connection
+ * iscsi_tcp_hdr_recv_done - process PDU header
  *
- * Notes:
- *      The function calls skb_copy_bits() and updates per-connection
- *      byte counters.
- **/
-static inline int
-iscsi_tcp_copy(struct iscsi_conn *conn, int buf_size)
-{
-        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-        int buf_left = buf_size - tcp_conn->data_copied;
-        int size = min(tcp_conn->in.copy, buf_left);
-        int rc;
-
-        debug_tcp("tcp_copy %d bytes at offset %d copied %d\n",
-               size, tcp_conn->in.offset, tcp_conn->data_copied);
-        BUG_ON(size <= 0);
-
-        rc = skb_copy_bits(tcp_conn->in.skb, tcp_conn->in.offset,
-                           (char*)conn->data + tcp_conn->data_copied, size);
-        BUG_ON(rc);
-
-        tcp_conn->in.offset += size;
-        tcp_conn->in.copy -= size;
-        tcp_conn->in.copied += size;
-        tcp_conn->data_copied += size;
-
-        if (buf_size != tcp_conn->data_copied)
-                return -EAGAIN;
-
-        return 0;
-}
-
-static inline void
-partial_sg_digest_update(struct hash_desc *desc, struct scatterlist *sg,
-                         int offset, int length)
-{
-        struct scatterlist temp;
-
-        sg_init_table(&temp, 1);
-        sg_set_page(&temp, sg_page(sg), length, offset);
-        crypto_hash_update(desc, &temp, length);
-}
-
-static void
-iscsi_recv_digest_update(struct iscsi_tcp_conn *tcp_conn, char* buf, int len)
-{
-        struct scatterlist tmp;
-
-        sg_init_one(&tmp, buf, len);
-        crypto_hash_update(&tcp_conn->rx_hash, &tmp, len);
-}
-
-static int iscsi_scsi_data_in(struct iscsi_conn *conn)
+ * This is the callback invoked when the PDU header has
+ * been received. If the header is followed by additional
+ * header segments, we go back for more data.
+ */
+static int
+iscsi_tcp_hdr_recv_done(struct iscsi_tcp_conn *tcp_conn,
+                        struct iscsi_segment *segment)
 {
-        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-        struct iscsi_cmd_task *ctask = tcp_conn->in.ctask;
-        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
-        struct scsi_cmnd *sc = ctask->sc;
-        struct scatterlist *sg;
-        int i, offset, rc = 0;
-
-        BUG_ON((void*)ctask != sc->SCp.ptr);
-
-        offset = tcp_ctask->data_offset;
-        sg = scsi_sglist(sc);
-
-        if (tcp_ctask->data_offset)
-                for (i = 0; i < tcp_ctask->sg_count; i++)
-                        offset -= sg[i].length;
-        /* we've passed through partial sg*/
-        if (offset < 0)
-                offset = 0;
-
-        for (i = tcp_ctask->sg_count; i < scsi_sg_count(sc); i++) {
-                char *dest;
-
-                dest = kmap_atomic(sg_page(&sg[i]), KM_SOFTIRQ0);
-                rc = iscsi_ctask_copy(tcp_conn, ctask, dest + sg[i].offset,
-                                      sg[i].length, offset);
-                kunmap_atomic(dest, KM_SOFTIRQ0);
-                if (rc == -EAGAIN)
-                        /* continue with the next SKB/PDU */
-                        return rc;
-                if (!rc) {
-                        if (conn->datadgst_en) {
-                                if (!offset)
-                                        crypto_hash_update(
-                                                        &tcp_conn->rx_hash,
-                                                        &sg[i], sg[i].length);
-                                else
-                                        partial_sg_digest_update(
-                                                        &tcp_conn->rx_hash,
-                                                        &sg[i],
-                                                        sg[i].offset + offset,
-                                                        sg[i].length - offset);
-                        }
-                        offset = 0;
-                        tcp_ctask->sg_count++;
-                }
-
-                if (!ctask->data_count) {
-                        if (rc && conn->datadgst_en)
-                                /*
-                                 * data-in is complete, but buffer not...
-                                 */
-                                partial_sg_digest_update(&tcp_conn->rx_hash,
-                                                         &sg[i],
-                                                         sg[i].offset,
-                                                         sg[i].length-rc);
-                        rc = 0;
-                        break;
-                }
-
-                if (!tcp_conn->in.copy)
-                        return -EAGAIN;
-        }
-        BUG_ON(ctask->data_count);
+        struct iscsi_conn *conn = tcp_conn->iscsi_conn;
+        struct iscsi_hdr *hdr;
 
-        /* check for non-exceptional status */
-        if (tcp_conn->in.hdr->flags & ISCSI_FLAG_DATA_STATUS) {
-                debug_scsi("done [sc %lx res %d itt 0x%x flags 0x%x]\n",
-                           (long)sc, sc->result, ctask->itt,
-                           tcp_conn->in.hdr->flags);
-                spin_lock(&conn->session->lock);
-                __iscsi_complete_pdu(conn, tcp_conn->in.hdr, NULL, 0);
-                spin_unlock(&conn->session->lock);
+        /* Check if there are additional header segments
+         * *prior* to computing the digest, because we
+         * may need to go back to the caller for more.
+         */
+        hdr = (struct iscsi_hdr *) tcp_conn->in.hdr_buf;
+        if (segment->copied == sizeof(struct iscsi_hdr) && hdr->hlength) {
+                /* Bump the header length - the caller will
+                 * just loop around and get the AHS for us, and
+                 * call again. */
+                unsigned int ahslen = hdr->hlength << 2;
+
+                /* Make sure we don't overflow */
+                if (sizeof(*hdr) + ahslen > sizeof(tcp_conn->in.hdr_buf))
+                        return ISCSI_ERR_AHSLEN;
+
+                segment->total_size += ahslen;
+                segment->size += ahslen;
+                return 0;
         }
 
-        return rc;
-}
-
-static int
-iscsi_data_recv(struct iscsi_conn *conn)
-{
-        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-        int rc = 0, opcode;
-
-        opcode = tcp_conn->in.hdr->opcode & ISCSI_OPCODE_MASK;
-        switch (opcode) {
-        case ISCSI_OP_SCSI_DATA_IN:
-                rc = iscsi_scsi_data_in(conn);
-                break;
-        case ISCSI_OP_SCSI_CMD_RSP:
-        case ISCSI_OP_TEXT_RSP:
-        case ISCSI_OP_LOGIN_RSP:
-        case ISCSI_OP_ASYNC_EVENT:
-        case ISCSI_OP_REJECT:
-                /*
-                 * Collect data segment to the connection's data
-                 * placeholder
-                 */
-                if (iscsi_tcp_copy(conn, tcp_conn->in.datalen)) {
-                        rc = -EAGAIN;
-                        goto exit;
+        /* We're done processing the header. See if we're doing
+         * header digests; if so, set up the recv_digest buffer
+         * and go back for more. */
+        if (conn->hdrdgst_en) {
+                if (segment->digest_len == 0) {
+                        iscsi_tcp_segment_splice_digest(segment,
+                                                        segment->recv_digest);
+                        return 0;
                 }
+                iscsi_tcp_dgst_header(&tcp_conn->rx_hash, hdr,
+                                      segment->total_copied - ISCSI_DIGEST_SIZE,
+                                      segment->digest);
 
-                rc = iscsi_complete_pdu(conn, tcp_conn->in.hdr, conn->data,
-                                        tcp_conn->in.datalen);
-                if (!rc && conn->datadgst_en && opcode != ISCSI_OP_LOGIN_RSP)
-                        iscsi_recv_digest_update(tcp_conn, conn->data,
-                                                tcp_conn->in.datalen);
-                break;
-        default:
-                BUG_ON(1);
+                if (!iscsi_tcp_dgst_verify(tcp_conn, segment))
+                        return ISCSI_ERR_HDR_DGST;
         }
-exit:
-        return rc;
+
+        tcp_conn->in.hdr = hdr;
+        return iscsi_tcp_hdr_dissect(conn, hdr);
 }
 
 /**
- * iscsi_tcp_data_recv - TCP receive in sendfile fashion
+ * iscsi_tcp_recv - TCP receive in sendfile fashion
  * @rd_desc: read descriptor
  * @skb: socket buffer
  * @offset: offset in skb
  * @len: skb->len - offset
  **/
 static int
-iscsi_tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
-                unsigned int offset, size_t len)
+iscsi_tcp_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
+               unsigned int offset, size_t len)
 {
-        int rc;
         struct iscsi_conn *conn = rd_desc->arg.data;
         struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-        int processed;
-        char pad[ISCSI_PAD_LEN];
-        struct scatterlist sg;
-
-        /*
-         * Save current SKB and its offset in the corresponding
-         * connection context.
-         */
-        tcp_conn->in.copy = skb->len - offset;
-        tcp_conn->in.offset = offset;
-        tcp_conn->in.skb = skb;
-        tcp_conn->in.len = tcp_conn->in.copy;
-        BUG_ON(tcp_conn->in.copy <= 0);
-        debug_tcp("in %d bytes\n", tcp_conn->in.copy);
+        struct iscsi_segment *segment = &tcp_conn->in.segment;
+        struct skb_seq_state seq;
+        unsigned int consumed = 0;
+        int rc = 0;
 
-more:
-        tcp_conn->in.copied = 0;
-        rc = 0;
+        debug_tcp("in %d bytes\n", skb->len - offset);
 
         if (unlikely(conn->suspend_rx)) {
                 debug_tcp("conn %d Rx suspended!\n", conn->id);
                 return 0;
         }
 
-        if (tcp_conn->in_progress == IN_PROGRESS_WAIT_HEADER ||
-            tcp_conn->in_progress == IN_PROGRESS_HEADER_GATHER) {
-                rc = iscsi_hdr_extract(tcp_conn);
-                if (rc) {
-                       if (rc == -EAGAIN)
-                                goto nomore;
-                       else {
-                                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
-                                return 0;
-                       }
-                }
+        skb_prepare_seq_read(skb, offset, skb->len, &seq);
+        while (1) {
+                unsigned int avail;
+                const u8 *ptr;
 
-                /*
-                 * Verify and process incoming PDU header.
-                 */
-                rc = iscsi_tcp_hdr_recv(conn);
-                if (!rc && tcp_conn->in.datalen) {
-                        if (conn->datadgst_en)
-                                crypto_hash_init(&tcp_conn->rx_hash);
-                        tcp_conn->in_progress = IN_PROGRESS_DATA_RECV;
-                } else if (rc) {
-                        iscsi_conn_failure(conn, rc);
-                        return 0;
+                avail = skb_seq_read(consumed, &ptr, &seq);
+                if (avail == 0) {
+                        debug_tcp("no more data avail. Consumed %d\n",
+                                  consumed);
+                        break;
                 }
-        }
-
-        if (tcp_conn->in_progress == IN_PROGRESS_DDIGEST_RECV &&
-            tcp_conn->in.copy) {
-                uint32_t recv_digest;
-
-                debug_tcp("extra data_recv offset %d copy %d\n",
-                          tcp_conn->in.offset, tcp_conn->in.copy);
-
-                if (!tcp_conn->data_copied) {
-                        if (tcp_conn->in.padding) {
-                                debug_tcp("padding -> %d\n",
-                                          tcp_conn->in.padding);
-                                memset(pad, 0, tcp_conn->in.padding);
-                                sg_init_one(&sg, pad, tcp_conn->in.padding);
-                                crypto_hash_update(&tcp_conn->rx_hash,
-                                                   &sg, sg.length);
+                BUG_ON(segment->copied >= segment->size);
+
+                debug_tcp("skb %p ptr=%p avail=%u\n", skb, ptr, avail);
+                rc = iscsi_tcp_segment_recv(tcp_conn, segment, ptr, avail);
+                BUG_ON(rc == 0);
+                consumed += rc;
+
+                if (segment->total_copied >= segment->total_size) {
+                        debug_tcp("segment done\n");
+                        rc = segment->done(tcp_conn, segment);
+                        if (rc != 0) {
+                                skb_abort_seq_read(&seq);
+                                goto error;
                         }
-                        crypto_hash_final(&tcp_conn->rx_hash,
-                                          (u8 *) &tcp_conn->in.datadgst);
-                        debug_tcp("rx digest 0x%x\n", tcp_conn->in.datadgst);
-                }
 
-                rc = iscsi_tcp_copy(conn, sizeof(uint32_t));
-                if (rc) {
-                        if (rc == -EAGAIN)
-                                goto again;
-                        iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
-                        return 0;
-                }
-
-                memcpy(&recv_digest, conn->data, sizeof(uint32_t));
-                if (recv_digest != tcp_conn->in.datadgst) {
-                        debug_tcp("iscsi_tcp: data digest error!"
-                                  "0x%x != 0x%x\n", recv_digest,
-                                  tcp_conn->in.datadgst);
-                        iscsi_conn_failure(conn, ISCSI_ERR_DATA_DGST);
-                        return 0;
-                } else {
-                        debug_tcp("iscsi_tcp: data digest match!"
-                                  "0x%x == 0x%x\n", recv_digest,
-                                  tcp_conn->in.datadgst);
-                        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
+                        /* The done() functions sets up the
+                         * next segment. */
                 }
         }
+        skb_abort_seq_read(&seq);
+        conn->rxdata_octets += consumed;
+        return consumed;
 
-        if (tcp_conn->in_progress == IN_PROGRESS_DATA_RECV &&
-            tcp_conn->in.copy) {
-                debug_tcp("data_recv offset %d copy %d\n",
-                       tcp_conn->in.offset, tcp_conn->in.copy);
-
-                rc = iscsi_data_recv(conn);
-                if (rc) {
-                        if (rc == -EAGAIN)
-                                goto again;
-                        iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
-                        return 0;
-                }
-
-                if (tcp_conn->in.padding)
-                        tcp_conn->in_progress = IN_PROGRESS_PAD_RECV;
-                else if (conn->datadgst_en)
-                        tcp_conn->in_progress = IN_PROGRESS_DDIGEST_RECV;
-                else
-                        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
-                tcp_conn->data_copied = 0;
-        }
-
-        if (tcp_conn->in_progress == IN_PROGRESS_PAD_RECV &&
-            tcp_conn->in.copy) {
-                int copylen = min(tcp_conn->in.padding - tcp_conn->data_copied,
-                                  tcp_conn->in.copy);
-
-                tcp_conn->in.copy -= copylen;
-                tcp_conn->in.offset += copylen;
-                tcp_conn->data_copied += copylen;
-
-                if (tcp_conn->data_copied != tcp_conn->in.padding)
-                        tcp_conn->in_progress = IN_PROGRESS_PAD_RECV;
-                else if (conn->datadgst_en)
-                        tcp_conn->in_progress = IN_PROGRESS_DDIGEST_RECV;
-                else
-                        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
-                tcp_conn->data_copied = 0;
-        }
-
-        debug_tcp("f, processed %d from out of %d padding %d\n",
-               tcp_conn->in.offset - offset, (int)len, tcp_conn->in.padding);
-        BUG_ON(tcp_conn->in.offset - offset > len);
-
-        if (tcp_conn->in.offset - offset != len) {
-                debug_tcp("continue to process %d bytes\n",
-                       (int)len - (tcp_conn->in.offset - offset));
-                goto more;
-        }
-
-nomore:
-        processed = tcp_conn->in.offset - offset;
-        BUG_ON(processed == 0);
-        return processed;
-
-again:
-        processed = tcp_conn->in.offset - offset;
-        debug_tcp("c, processed %d from out of %d rd_desc_cnt %d\n",
-                  processed, (int)len, (int)rd_desc->count);
-        BUG_ON(processed == 0);
-        BUG_ON(processed > len);
-
-        conn->rxdata_octets += processed;
-        return processed;
+error:
+        debug_tcp("Error receiving PDU, errno=%d\n", rc);
+        iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
+        return 0;
 }
 
 static void
 iscsi_tcp_data_ready(struct sock *sk, int flag)
 {
         struct iscsi_conn *conn = sk->sk_user_data;
+        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
         read_descriptor_t rd_desc;
 
         read_lock(&sk->sk_callback_lock);
 
         /*
-         * Use rd_desc to pass 'conn' to iscsi_tcp_data_recv.
+         * Use rd_desc to pass 'conn' to iscsi_tcp_recv.
          * We set count to 1 because we want the network layer to
-         * hand us all the skbs that are available. iscsi_tcp_data_recv
+         * hand us all the skbs that are available. iscsi_tcp_recv
          * handled pdus that cross buffers or pdus that still need data.
          */
         rd_desc.arg.data = conn;
         rd_desc.count = 1;
-        tcp_read_sock(sk, &rd_desc, iscsi_tcp_data_recv);
+        tcp_read_sock(sk, &rd_desc, iscsi_tcp_recv);
 
         read_unlock(&sk->sk_callback_lock);
+
+        /* If we had to (atomically) map a highmem page,
+         * unmap it now. */
+        iscsi_tcp_segment_unmap(&tcp_conn->in.segment);
 }
 
 static void
@@ -1077,121 +1079,173 @@ iscsi_conn_restore_callbacks(struct iscsi_tcp_conn *tcp_conn)
 }
 
 /**
- * iscsi_send - generic send routine
- * @sk: kernel's socket
- * @buf: buffer to write from
- * @size: actual size to write
- * @flags: socket's flags
- */
-static inline int
-iscsi_send(struct iscsi_conn *conn, struct iscsi_buf *buf, int size, int flags)
+ * iscsi_xmit - TCP transmit
+ **/
+static int
+iscsi_xmit(struct iscsi_conn *conn)
 {
         struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-        struct socket *sk = tcp_conn->sock;
-        int offset = buf->sg.offset + buf->sent, res;
+        struct iscsi_segment *segment = &tcp_conn->out.segment;
+        unsigned int consumed = 0;
+        int rc = 0;
 
-        /*
-         * if we got use_sg=0 or are sending something we kmallocd
-         * then we did not have to do kmap (kmap returns page_address)
-         *
-         * if we got use_sg > 0, but had to drop down, we do not
-         * set clustering so this should only happen for that
-         * slab case.
-         */
-        if (buf->use_sendmsg)
-                res = sock_no_sendpage(sk, sg_page(&buf->sg), offset, size, flags);
-        else
-                res = tcp_conn->sendpage(sk, sg_page(&buf->sg), offset, size, flags);
-
-        if (res >= 0) {
-                conn->txdata_octets += res;
-                buf->sent += res;
-                return res;
+        while (1) {
+                rc = iscsi_tcp_xmit_segment(tcp_conn, segment);
+                if (rc < 0)
+                        goto error;
+                if (rc == 0)
+                        break;
+
+                consumed += rc;
+
+                if (segment->total_copied >= segment->total_size) {
+                        if (segment->done != NULL) {
+                                rc = segment->done(tcp_conn, segment);
+                                if (rc < 0)
+                                        goto error;
+                        }
+                }
         }
 
-        tcp_conn->sendpage_failures_cnt++;
-        if (res == -EAGAIN)
-                res = -ENOBUFS;
-        else
-                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
-        return res;
+        debug_tcp("xmit %d bytes\n", consumed);
+
+        conn->txdata_octets += consumed;
+        return consumed;
+
+error:
+        /* Transmit error. We could initiate error recovery
+         * here. */
+        debug_tcp("Error sending PDU, errno=%d\n", rc);
+        iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
+        return rc;
 }
 
 /**
- * iscsi_sendhdr - send PDU Header via tcp_sendpage()
- * @conn: iscsi connection
- * @buf: buffer to write from
- * @datalen: lenght of data to be sent after the header
- *
- * Notes:
- *      (Tx, Fast Path)
- **/
+ * iscsi_tcp_xmit_qlen - return the number of bytes queued for xmit
+ */
 static inline int
-iscsi_sendhdr(struct iscsi_conn *conn, struct iscsi_buf *buf, int datalen)
+iscsi_tcp_xmit_qlen(struct iscsi_conn *conn)
 {
-        int flags = 0; /* MSG_DONTWAIT; */
-        int res, size;
-
-        size = buf->sg.length - buf->sent;
-        BUG_ON(buf->sent + size > buf->sg.length);
-        if (buf->sent + size != buf->sg.length || datalen)
-                flags |= MSG_MORE;
-
-        res = iscsi_send(conn, buf, size, flags);
-        debug_tcp("sendhdr %d bytes, sent %d res %d\n", size, buf->sent, res);
-        if (res >= 0) {
-                if (size != res)
-                        return -EAGAIN;
-                return 0;
-        }
+        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
+        struct iscsi_segment *segment = &tcp_conn->out.segment;
 
-        return res;
+        return segment->total_copied - segment->total_size;
 }
 
-/**
- * iscsi_sendpage - send one page of iSCSI Data-Out.
- * @conn: iscsi connection
- * @buf: buffer to write from
- * @count: remaining data
- * @sent: number of bytes sent
- *
- * Notes:
- *      (Tx, Fast Path)
- **/
 static inline int
-iscsi_sendpage(struct iscsi_conn *conn, struct iscsi_buf *buf,
-               int *count, int *sent)
+iscsi_tcp_flush(struct iscsi_conn *conn)
 {
-        int flags = 0; /* MSG_DONTWAIT; */
-        int res, size;
-
-        size = buf->sg.length - buf->sent;
-        BUG_ON(buf->sent + size > buf->sg.length);
-        if (size > *count)
-                size = *count;
-        if (buf->sent + size != buf->sg.length || *count != size)
-                flags |= MSG_MORE;
-
-        res = iscsi_send(conn, buf, size, flags);
-        debug_tcp("sendpage: %d bytes, sent %d left %d sent %d res %d\n",
-                  size, buf->sent, *count, *sent, res);
-        if (res >= 0) {
-                *count -= res;
-                *sent += res;
-                if (size != res)
+        int rc;
+
+        while (iscsi_tcp_xmit_qlen(conn)) {
+                rc = iscsi_xmit(conn);
+                if (rc == 0)
                         return -EAGAIN;
-                return 0;
+                if (rc < 0)
+                        return rc;
         }
 
-        return res;
+        return 0;
 }
 
-static inline void
-iscsi_data_digest_init(struct iscsi_tcp_conn *tcp_conn,
-                      struct iscsi_tcp_cmd_task *tcp_ctask)
+/*
+ * This is called when we're done sending the header.
+ * Simply copy the data_segment to the send segment, and return.
+ */
+static int
+iscsi_tcp_send_hdr_done(struct iscsi_tcp_conn *tcp_conn,
+                        struct iscsi_segment *segment)
+{
+        tcp_conn->out.segment = tcp_conn->out.data_segment;
+        debug_tcp("Header done. Next segment size %u total_size %u\n",
+                  tcp_conn->out.segment.size, tcp_conn->out.segment.total_size);
+        return 0;
+}
+
+static void
+iscsi_tcp_send_hdr_prep(struct iscsi_conn *conn, void *hdr, size_t hdrlen)
 {
-        crypto_hash_init(&tcp_conn->tx_hash);
-        tcp_ctask->digest_count = 4;
+        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
+
+        debug_tcp("%s(%p%s)\n", __FUNCTION__, tcp_conn,
+                        conn->hdrdgst_en? ", digest enabled" : "");
+
+        /* Clear the data segment - needs to be filled in by the
+         * caller using iscsi_tcp_send_data_prep() */
+        memset(&tcp_conn->out.data_segment, 0, sizeof(struct iscsi_segment));
+
+        /* If header digest is enabled, compute the CRC and
+         * place the digest into the same buffer. We make
+         * sure that both iscsi_tcp_ctask and mtask have
+         * sufficient room.
+         */
+        if (conn->hdrdgst_en) {
+                iscsi_tcp_dgst_header(&tcp_conn->tx_hash, hdr, hdrlen,
+                                      hdr + hdrlen);
+                hdrlen += ISCSI_DIGEST_SIZE;
+        }
+
+        /* Remember header pointer for later, when we need
+         * to decide whether there's a payload to go along
+         * with the header. */
+        tcp_conn->out.hdr = hdr;
+
+        iscsi_segment_init_linear(&tcp_conn->out.segment, hdr, hdrlen,
+                                iscsi_tcp_send_hdr_done, NULL);
+}
+
+/*
+ * Prepare the send buffer for the payload data.
+ * Padding and checksumming will all be taken care
+ * of by the iscsi_segment routines.
+ */
+static int
+iscsi_tcp_send_data_prep(struct iscsi_conn *conn, struct scatterlist *sg,
+                         unsigned int count, unsigned int offset,
+                         unsigned int len)
+{
+        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
+        struct hash_desc *tx_hash = NULL;
+        unsigned int hdr_spec_len;
+
+        debug_tcp("%s(%p, offset=%d, datalen=%d%s)\n", __FUNCTION__,
+                        tcp_conn, offset, len,
+                        conn->datadgst_en? ", digest enabled" : "");
+
+        /* Make sure the datalen matches what the caller
+           said he would send. */
+        hdr_spec_len = ntoh24(tcp_conn->out.hdr->dlength);
+        WARN_ON(iscsi_padded(len) != iscsi_padded(hdr_spec_len));
+
+        if (conn->datadgst_en)
+                tx_hash = &tcp_conn->tx_hash;
+
+        return iscsi_segment_seek_sg(&tcp_conn->out.data_segment,
+                                   sg, count, offset, len,
+                                   NULL, tx_hash);
+}
+
+static void
+iscsi_tcp_send_linear_data_prepare(struct iscsi_conn *conn, void *data,
+                                   size_t len)
+{
+        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
+        struct hash_desc *tx_hash = NULL;
+        unsigned int hdr_spec_len;
+
+        debug_tcp("%s(%p, datalen=%d%s)\n", __FUNCTION__, tcp_conn, len,
+                  conn->datadgst_en? ", digest enabled" : "");
+
+        /* Make sure the datalen matches what the caller
+           said he would send. */
+        hdr_spec_len = ntoh24(tcp_conn->out.hdr->dlength);
+        WARN_ON(iscsi_padded(len) != iscsi_padded(hdr_spec_len));
+
+        if (conn->datadgst_en)
+                tx_hash = &tcp_conn->tx_hash;
+
+        iscsi_segment_init_linear(&tcp_conn->out.data_segment,
+                                data, len, NULL, tx_hash);
 }
 
 /**
@@ -1207,12 +1261,17 @@ iscsi_data_digest_init(struct iscsi_tcp_conn *tcp_conn,
  *
  *      Called under connection lock.
  **/
-static void
+static int
 iscsi_solicit_data_cont(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask,
-                        struct iscsi_r2t_info *r2t, int left)
+                        struct iscsi_r2t_info *r2t)
 {
         struct iscsi_data *hdr;
-        int new_offset;
+        int new_offset, left;
+
+        BUG_ON(r2t->data_length - r2t->sent < 0);
+        left = r2t->data_length - r2t->sent;
+        if (left == 0)
+                return 0;
 
         hdr = &r2t->dtask.hdr;
         memset(hdr, 0, sizeof(struct iscsi_data));
@@ -1233,43 +1292,46 @@ iscsi_solicit_data_cont(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask,
                 r2t->data_count = left;
                 hdr->flags = ISCSI_FLAG_CMD_FINAL;
         }
-        conn->dataout_pdus_cnt++;
-
-        iscsi_buf_init_iov(&r2t->headbuf, (char*)hdr,
-                           sizeof(struct iscsi_hdr));
-
-        if (iscsi_buf_left(&r2t->sendbuf))
-                return;
-
-        iscsi_buf_init_sg(&r2t->sendbuf, r2t->sg);
-        r2t->sg += 1;
-}
 
-static void iscsi_set_padding(struct iscsi_tcp_cmd_task *tcp_ctask,
-                              unsigned long len)
-{
-        tcp_ctask->pad_count = len & (ISCSI_PAD_LEN - 1);
-        if (!tcp_ctask->pad_count)
-                return;
-
-        tcp_ctask->pad_count = ISCSI_PAD_LEN - tcp_ctask->pad_count;
-        debug_scsi("write padding %d bytes\n", tcp_ctask->pad_count);
-        set_bit(XMSTATE_BIT_W_PAD, &tcp_ctask->xmstate);
+        conn->dataout_pdus_cnt++;
+        return 1;
 }
 
 /**
- * iscsi_tcp_cmd_init - Initialize iSCSI SCSI_READ or SCSI_WRITE commands
+ * iscsi_tcp_ctask - Initialize iSCSI SCSI_READ or SCSI_WRITE commands
  * @conn: iscsi connection
  * @ctask: scsi command task
  * @sc: scsi command
  **/
-static void
-iscsi_tcp_cmd_init(struct iscsi_cmd_task *ctask)
+static int
+iscsi_tcp_ctask_init(struct iscsi_cmd_task *ctask)
 {
         struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
+        struct iscsi_conn *conn = ctask->conn;
+        struct scsi_cmnd *sc = ctask->sc;
+        int err;
 
         BUG_ON(__kfifo_len(tcp_ctask->r2tqueue));
-        tcp_ctask->xmstate = 1 << XMSTATE_BIT_CMD_HDR_INIT;
+        tcp_ctask->sent = 0;
+        tcp_ctask->exp_datasn = 0;
+
+        /* Prepare PDU, optionally w/ immediate data */
+        debug_scsi("ctask deq [cid %d itt 0x%x imm %d unsol %d]\n",
+                    conn->id, ctask->itt, ctask->imm_count,
+                    ctask->unsol_count);
+        iscsi_tcp_send_hdr_prep(conn, ctask->hdr, ctask->hdr_len);
+
+        if (!ctask->imm_count)
+                return 0;
+
+        /* If we have immediate data, attach a payload */
+        err = iscsi_tcp_send_data_prep(conn, scsi_sglist(sc), scsi_sg_count(sc),
+                                       0, ctask->imm_count);
+        if (err)
+                return err;
+        tcp_ctask->sent += ctask->imm_count;
+        ctask->imm_count = 0;
+        return 0;
 }
 
 /**
@@ -1281,484 +1343,130 @@ iscsi_tcp_cmd_init(struct iscsi_cmd_task *ctask)
  *      The function can return -EAGAIN in which case caller must
  *      call it again later, or recover. '0' return code means successful
  *      xmit.
- *
- *      Management xmit state machine consists of these states:
- *              XMSTATE_BIT_IMM_HDR_INIT - calculate digest of PDU Header
- *              XMSTATE_BIT_IMM_HDR      - PDU Header xmit in progress
- *              XMSTATE_BIT_IMM_DATA     - PDU Data xmit in progress
- *              XMSTATE_VALUE_IDLE       - management PDU is done
  **/
 static int
 iscsi_tcp_mtask_xmit(struct iscsi_conn *conn, struct iscsi_mgmt_task *mtask)
 {
-        struct iscsi_tcp_mgmt_task *tcp_mtask = mtask->dd_data;
         int rc;
 
-        debug_scsi("mtask deq [cid %d state %x itt 0x%x]\n",
-                conn->id, tcp_mtask->xmstate, mtask->itt);
-
-        if (test_bit(XMSTATE_BIT_IMM_HDR_INIT, &tcp_mtask->xmstate)) {
-                iscsi_buf_init_iov(&tcp_mtask->headbuf, (char*)mtask->hdr,
-                                   sizeof(struct iscsi_hdr));
-
-                if (mtask->data_count) {
-                        set_bit(XMSTATE_BIT_IMM_DATA, &tcp_mtask->xmstate);
-                        iscsi_buf_init_iov(&tcp_mtask->sendbuf,
-                                           (char*)mtask->data,
-                                           mtask->data_count);
-                }
-
-                if (conn->c_stage != ISCSI_CONN_INITIAL_STAGE &&
-                    conn->stop_stage != STOP_CONN_RECOVER &&
-                    conn->hdrdgst_en)
-                        iscsi_hdr_digest(conn, &tcp_mtask->headbuf,
-                                        (u8*)tcp_mtask->hdrext);
-
-                tcp_mtask->sent = 0;
-                clear_bit(XMSTATE_BIT_IMM_HDR_INIT, &tcp_mtask->xmstate);
-                set_bit(XMSTATE_BIT_IMM_HDR, &tcp_mtask->xmstate);
-        }
-
-        if (test_bit(XMSTATE_BIT_IMM_HDR, &tcp_mtask->xmstate)) {
-                rc = iscsi_sendhdr(conn, &tcp_mtask->headbuf,
-                                   mtask->data_count);
-                if (rc)
-                        return rc;
-                clear_bit(XMSTATE_BIT_IMM_HDR, &tcp_mtask->xmstate);
-        }
-
-        if (test_and_clear_bit(XMSTATE_BIT_IMM_DATA, &tcp_mtask->xmstate)) {
-                BUG_ON(!mtask->data_count);
-                /* FIXME: implement.
-                 * Virtual buffer could be spreaded across multiple pages...
-                 */
-                do {
-                        int rc;
-
-                        rc = iscsi_sendpage(conn, &tcp_mtask->sendbuf,
-                                        &mtask->data_count, &tcp_mtask->sent);
-                        if (rc) {
-                                set_bit(XMSTATE_BIT_IMM_DATA, &tcp_mtask->xmstate);
-                                return rc;
-                        }
-                } while (mtask->data_count);
-        }
+        /* Flush any pending data first. */
+        rc = iscsi_tcp_flush(conn);
+        if (rc < 0)
+                return rc;
 
-        BUG_ON(tcp_mtask->xmstate != XMSTATE_VALUE_IDLE);
         if (mtask->hdr->itt == RESERVED_ITT) {
                 struct iscsi_session *session = conn->session;
 
                 spin_lock_bh(&session->lock);
-                list_del(&conn->mtask->running);
-                __kfifo_put(session->mgmtpool.queue, (void*)&conn->mtask,
-                            sizeof(void*));
+                iscsi_free_mgmt_task(conn, mtask);
                 spin_unlock_bh(&session->lock);
         }
+
         return 0;
 }
 
+/*
+ * iscsi_tcp_ctask_xmit - xmit normal PDU task
+ * @conn: iscsi connection
+ * @ctask: iscsi command task
+ *
+ * We're expected to return 0 when everything was transmitted succesfully,
+ * -EAGAIN if there's still data in the queue, or != 0 for any other kind
+ * of error.
+ */
 static int
-iscsi_send_cmd_hdr(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
+iscsi_tcp_ctask_xmit(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
 {
-        struct scsi_cmnd *sc = ctask->sc;
         struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
+        struct scsi_cmnd *sc = ctask->sc;
         int rc = 0;
 
-        if (test_bit(XMSTATE_BIT_CMD_HDR_INIT, &tcp_ctask->xmstate)) {
-                tcp_ctask->sent = 0;
-                tcp_ctask->sg_count = 0;
-                tcp_ctask->exp_datasn = 0;
-
-                if (sc->sc_data_direction == DMA_TO_DEVICE) {
-                        struct scatterlist *sg = scsi_sglist(sc);
-
-                        iscsi_buf_init_sg(&tcp_ctask->sendbuf, sg);
-                        tcp_ctask->sg = sg + 1;
-                        tcp_ctask->bad_sg = sg + scsi_sg_count(sc);
-
-                        debug_scsi("cmd [itt 0x%x total %d imm_data %d "
-                                   "unsol count %d, unsol offset %d]\n",
-                                   ctask->itt, scsi_bufflen(sc),
-                                   ctask->imm_count, ctask->unsol_count,
-                                   ctask->unsol_offset);
-                }
-
-                iscsi_buf_init_iov(&tcp_ctask->headbuf, (char*)ctask->hdr,
-                                  sizeof(struct iscsi_hdr));
-
-                if (conn->hdrdgst_en)
-                        iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
-                                         (u8*)tcp_ctask->hdrext);
-                clear_bit(XMSTATE_BIT_CMD_HDR_INIT, &tcp_ctask->xmstate);
-                set_bit(XMSTATE_BIT_CMD_HDR_XMIT, &tcp_ctask->xmstate);
-        }
-
-        if (test_bit(XMSTATE_BIT_CMD_HDR_XMIT, &tcp_ctask->xmstate)) {
-                rc = iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->imm_count);
-                if (rc)
-                        return rc;
-                clear_bit(XMSTATE_BIT_CMD_HDR_XMIT, &tcp_ctask->xmstate);
-
-                if (sc->sc_data_direction != DMA_TO_DEVICE)
-                        return 0;
-
-                if (ctask->imm_count) {
-                        set_bit(XMSTATE_BIT_IMM_DATA, &tcp_ctask->xmstate);
-                        iscsi_set_padding(tcp_ctask, ctask->imm_count);
-
-                        if (ctask->conn->datadgst_en) {
-                                iscsi_data_digest_init(ctask->conn->dd_data,
-                                                       tcp_ctask);
-                                tcp_ctask->immdigest = 0;
-                        }
-                }
-
-                if (ctask->unsol_count) {
-                        set_bit(XMSTATE_BIT_UNS_HDR, &tcp_ctask->xmstate);
-                        set_bit(XMSTATE_BIT_UNS_INIT, &tcp_ctask->xmstate);
-                }
-        }
-        return rc;
-}
-
-static int
-iscsi_send_padding(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
-{
-        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
-        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-        int sent = 0, rc;
-
-        if (test_bit(XMSTATE_BIT_W_PAD, &tcp_ctask->xmstate)) {
-                iscsi_buf_init_iov(&tcp_ctask->sendbuf, (char*)&tcp_ctask->pad,
-                                   tcp_ctask->pad_count);
-                if (conn->datadgst_en)
-                        crypto_hash_update(&tcp_conn->tx_hash,
-                                           &tcp_ctask->sendbuf.sg,
-                                           tcp_ctask->sendbuf.sg.length);
-        } else if (!test_bit(XMSTATE_BIT_W_RESEND_PAD, &tcp_ctask->xmstate))
-                return 0;
-
-        clear_bit(XMSTATE_BIT_W_PAD, &tcp_ctask->xmstate);
-        clear_bit(XMSTATE_BIT_W_RESEND_PAD, &tcp_ctask->xmstate);
-        debug_scsi("sending %d pad bytes for itt 0x%x\n",
-                   tcp_ctask->pad_count, ctask->itt);
-        rc = iscsi_sendpage(conn, &tcp_ctask->sendbuf, &tcp_ctask->pad_count,
-                           &sent);
-        if (rc) {
-                debug_scsi("padding send failed %d\n", rc);
-                set_bit(XMSTATE_BIT_W_RESEND_PAD, &tcp_ctask->xmstate);
-        }
-        return rc;
-}
-
-static int
-iscsi_send_digest(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask,
-                        struct iscsi_buf *buf, uint32_t *digest)
-{
-        struct iscsi_tcp_cmd_task *tcp_ctask;
-        struct iscsi_tcp_conn *tcp_conn;
-        int rc, sent = 0;
-
-        if (!conn->datadgst_en)
-                return 0;
-
-        tcp_ctask = ctask->dd_data;
-        tcp_conn = conn->dd_data;
-
-        if (!test_bit(XMSTATE_BIT_W_RESEND_DATA_DIGEST, &tcp_ctask->xmstate)) {
-                crypto_hash_final(&tcp_conn->tx_hash, (u8*)digest);
-                iscsi_buf_init_iov(buf, (char*)digest, 4);
-        }
-        clear_bit(XMSTATE_BIT_W_RESEND_DATA_DIGEST, &tcp_ctask->xmstate);
-
-        rc = iscsi_sendpage(conn, buf, &tcp_ctask->digest_count, &sent);
-        if (!rc)
-                debug_scsi("sent digest 0x%x for itt 0x%x\n", *digest,
-                          ctask->itt);
-        else {
-                debug_scsi("sending digest 0x%x failed for itt 0x%x!\n",
-                          *digest, ctask->itt);
-                set_bit(XMSTATE_BIT_W_RESEND_DATA_DIGEST, &tcp_ctask->xmstate);
-        }
-        return rc;
-}
-
-static int
-iscsi_send_data(struct iscsi_cmd_task *ctask, struct iscsi_buf *sendbuf,
-                struct scatterlist **sg, int *sent, int *count,
-                struct iscsi_buf *digestbuf, uint32_t *digest)
-{
-        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
-        struct iscsi_conn *conn = ctask->conn;
-        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
-        int rc, buf_sent, offset;
-
-        while (*count) {
-                buf_sent = 0;
-                offset = sendbuf->sent;
-
-                rc = iscsi_sendpage(conn, sendbuf, count, &buf_sent);
-                *sent = *sent + buf_sent;
-                if (buf_sent && conn->datadgst_en)
-                        partial_sg_digest_update(&tcp_conn->tx_hash,
-                                &sendbuf->sg, sendbuf->sg.offset + offset,
-                                buf_sent);
-                if (!iscsi_buf_left(sendbuf) && *sg != tcp_ctask->bad_sg) {
-                        iscsi_buf_init_sg(sendbuf, *sg);
-                        *sg = *sg + 1;
-                }
-
-                if (rc)
-                        return rc;
-        }
-
-        rc = iscsi_send_padding(conn, ctask);
-        if (rc)
+flush:
+        /* Flush any pending data first. */
+        rc = iscsi_tcp_flush(conn);
+        if (rc < 0)
                 return rc;
 
-        return iscsi_send_digest(conn, ctask, digestbuf, digest);
-}
-
-static int
-iscsi_send_unsol_hdr(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
-{
-        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
-        struct iscsi_data_task *dtask;
-        int rc;
-
-        set_bit(XMSTATE_BIT_UNS_DATA, &tcp_ctask->xmstate);
-        if (test_bit(XMSTATE_BIT_UNS_INIT, &tcp_ctask->xmstate)) {
-                dtask = &tcp_ctask->unsol_dtask;
-
-                iscsi_prep_unsolicit_data_pdu(ctask, &dtask->hdr);
-                iscsi_buf_init_iov(&tcp_ctask->headbuf, (char*)&dtask->hdr,
-                                   sizeof(struct iscsi_hdr));
-                if (conn->hdrdgst_en)
-                        iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
-                                        (u8*)dtask->hdrext);
-
-                clear_bit(XMSTATE_BIT_UNS_INIT, &tcp_ctask->xmstate);
-                iscsi_set_padding(tcp_ctask, ctask->data_count);
-        }
-
-        rc = iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->data_count);
-        if (rc) {
-                clear_bit(XMSTATE_BIT_UNS_DATA, &tcp_ctask->xmstate);
-                set_bit(XMSTATE_BIT_UNS_HDR, &tcp_ctask->xmstate);
-                return rc;
-        }
+        /* Are we done already? */
+        if (sc->sc_data_direction != DMA_TO_DEVICE)
+                return 0;
 
-        if (conn->datadgst_en) {
-                dtask = &tcp_ctask->unsol_dtask;
-                iscsi_data_digest_init(ctask->conn->dd_data, tcp_ctask);
-                dtask->digest = 0;
-        }
+        if (ctask->unsol_count != 0) {
+                struct iscsi_data *hdr = &tcp_ctask->unsol_dtask.hdr;
 
-        debug_scsi("uns dout [itt 0x%x dlen %d sent %d]\n",
-                   ctask->itt, ctask->unsol_count, tcp_ctask->sent);
-        return 0;
-}
+                /* Prepare a header for the unsolicited PDU.
+                 * The amount of data we want to send will be
+                 * in ctask->data_count.
+                 * FIXME: return the data count instead.
+                 */
+                iscsi_prep_unsolicit_data_pdu(ctask, hdr);
 
-static int
-iscsi_send_unsol_pdu(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
-{
-        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
-        int rc;
+                debug_tcp("unsol dout [itt 0x%x doff %d dlen %d]\n",
+                                ctask->itt, tcp_ctask->sent, ctask->data_count);
 
-        if (test_and_clear_bit(XMSTATE_BIT_UNS_HDR, &tcp_ctask->xmstate)) {
-                BUG_ON(!ctask->unsol_count);
-send_hdr:
-                rc = iscsi_send_unsol_hdr(conn, ctask);
+                iscsi_tcp_send_hdr_prep(conn, hdr, sizeof(*hdr));
+                rc = iscsi_tcp_send_data_prep(conn, scsi_sglist(sc),
+                                              scsi_sg_count(sc),
+                                              tcp_ctask->sent,
+                                              ctask->data_count);
                 if (rc)
-                        return rc;
-        }
-
-        if (test_bit(XMSTATE_BIT_UNS_DATA, &tcp_ctask->xmstate)) {
-                struct iscsi_data_task *dtask = &tcp_ctask->unsol_dtask;
-                int start = tcp_ctask->sent;
+                        goto fail;
+                tcp_ctask->sent += ctask->data_count;
+                ctask->unsol_count -= ctask->data_count;
+                goto flush;
+        } else {
+                struct iscsi_session *session = conn->session;
+                struct iscsi_r2t_info *r2t;
 
-                rc = iscsi_send_data(ctask, &tcp_ctask->sendbuf, &tcp_ctask->sg,
-                                     &tcp_ctask->sent, &ctask->data_count,
-                                     &dtask->digestbuf, &dtask->digest);
-                ctask->unsol_count -= tcp_ctask->sent - start;
-                if (rc)
-                        return rc;
-                clear_bit(XMSTATE_BIT_UNS_DATA, &tcp_ctask->xmstate);
-                /*
-                 * Done with the Data-Out. Next, check if we need
-                 * to send another unsolicited Data-Out.
+                /* All unsolicited PDUs sent. Check for solicited PDUs.
                  */
-                if (ctask->unsol_count) {
-                        debug_scsi("sending more uns\n");
-                        set_bit(XMSTATE_BIT_UNS_INIT, &tcp_ctask->xmstate);
-                        goto send_hdr;
+                spin_lock_bh(&session->lock);
+                r2t = tcp_ctask->r2t;
+                if (r2t != NULL) {
+                        /* Continue with this R2T? */
+                        if (!iscsi_solicit_data_cont(conn, ctask, r2t)) {
+                                debug_scsi("  done with r2t %p\n", r2t);
+
+                                __kfifo_put(tcp_ctask->r2tpool.queue,
+                                            (void*)&r2t, sizeof(void*));
+                                tcp_ctask->r2t = r2t = NULL;
+                        }
                 }
-        }
-        return 0;
-}
-
-static int iscsi_send_sol_pdu(struct iscsi_conn *conn,
-                              struct iscsi_cmd_task *ctask)
-{
-        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
-        struct iscsi_session *session = conn->session;
-        struct iscsi_r2t_info *r2t;
-        struct iscsi_data_task *dtask;
-        int left, rc;
 
-        if (test_bit(XMSTATE_BIT_SOL_HDR_INIT, &tcp_ctask->xmstate)) {
-                if (!tcp_ctask->r2t) {
-                        spin_lock_bh(&session->lock);
+                if (r2t == NULL) {
                         __kfifo_get(tcp_ctask->r2tqueue, (void*)&tcp_ctask->r2t,
                                     sizeof(void*));
-                        spin_unlock_bh(&session->lock);
+                        r2t = tcp_ctask->r2t;
                 }
-send_hdr:
-                r2t = tcp_ctask->r2t;
-                dtask = &r2t->dtask;
-
-                if (conn->hdrdgst_en)
-                        iscsi_hdr_digest(conn, &r2t->headbuf,
-                                        (u8*)dtask->hdrext);
-                clear_bit(XMSTATE_BIT_SOL_HDR_INIT, &tcp_ctask->xmstate);
-                set_bit(XMSTATE_BIT_SOL_HDR, &tcp_ctask->xmstate);
-        }
-
-        if (test_bit(XMSTATE_BIT_SOL_HDR, &tcp_ctask->xmstate)) {
-                r2t = tcp_ctask->r2t;
-                dtask = &r2t->dtask;
-
-                rc = iscsi_sendhdr(conn, &r2t->headbuf, r2t->data_count);
-                if (rc)
-                        return rc;
-                clear_bit(XMSTATE_BIT_SOL_HDR, &tcp_ctask->xmstate);
-                set_bit(XMSTATE_BIT_SOL_DATA, &tcp_ctask->xmstate);
+                spin_unlock_bh(&session->lock);
 
-                if (conn->datadgst_en) {
-                        iscsi_data_digest_init(conn->dd_data, tcp_ctask);
-                        dtask->digest = 0;
+                /* Waiting for more R2Ts to arrive. */
+                if (r2t == NULL) {
+                        debug_tcp("no R2Ts yet\n");
+                        return 0;
                 }
 
-                iscsi_set_padding(tcp_ctask, r2t->data_count);
-                debug_scsi("sol dout [dsn %d itt 0x%x dlen %d sent %d]\n",
-                        r2t->solicit_datasn - 1, ctask->itt, r2t->data_count,
-                        r2t->sent);
-        }
+                debug_scsi("sol dout %p [dsn %d itt 0x%x doff %d dlen %d]\n",
+                        r2t, r2t->solicit_datasn - 1, ctask->itt,
+                        r2t->data_offset + r2t->sent, r2t->data_count);
 
-        if (test_bit(XMSTATE_BIT_SOL_DATA, &tcp_ctask->xmstate)) {
-                r2t = tcp_ctask->r2t;
-                dtask = &r2t->dtask;
+                iscsi_tcp_send_hdr_prep(conn, &r2t->dtask.hdr,
+                                        sizeof(struct iscsi_hdr));
 
-                rc = iscsi_send_data(ctask, &r2t->sendbuf, &r2t->sg,
-                                     &r2t->sent, &r2t->data_count,
-                                     &dtask->digestbuf, &dtask->digest);
+                rc = iscsi_tcp_send_data_prep(conn, scsi_sglist(sc),
+                                              scsi_sg_count(sc),
+                                              r2t->data_offset + r2t->sent,
+                                              r2t->data_count);
                 if (rc)
-                        return rc;
-                clear_bit(XMSTATE_BIT_SOL_DATA, &tcp_ctask->xmstate);
-
-                /*
-                 * Done with this Data-Out. Next, check if we have
-                 * to send another Data-Out for this R2T.
-                 */
-                BUG_ON(r2t->data_length - r2t->sent < 0);
-                left = r2t->data_length - r2t->sent;
-                if (left) {
-                        iscsi_solicit_data_cont(conn, ctask, r2t, left);
-                        goto send_hdr;
-                }
-
-                /*
-                 * Done with this R2T. Check if there are more
-                 * outstanding R2Ts ready to be processed.
-                 */
-                spin_lock_bh(&session->lock);
-                tcp_ctask->r2t = NULL;
-                __kfifo_put(tcp_ctask->r2tpool.queue, (void*)&r2t,
-                            sizeof(void*));
-                if (__kfifo_get(tcp_ctask->r2tqueue, (void*)&r2t,
-                                sizeof(void*))) {
-                        tcp_ctask->r2t = r2t;
-                        spin_unlock_bh(&session->lock);
-                        goto send_hdr;
-                }
-                spin_unlock_bh(&session->lock);
+                        goto fail;
+                tcp_ctask->sent += r2t->data_count;
+                r2t->sent += r2t->data_count;
+                goto flush;
         }
         return 0;
-}
-
-/**
- * iscsi_tcp_ctask_xmit - xmit normal PDU task
- * @conn: iscsi connection
- * @ctask: iscsi command task
- *
- * Notes:
- *      The function can return -EAGAIN in which case caller must
- *      call it again later, or recover. '0' return code means successful
- *      xmit.
- *      The function is devided to logical helpers (above) for the different
- *      xmit stages.
- *
- *iscsi_send_cmd_hdr()
- *      XMSTATE_BIT_CMD_HDR_INIT - prepare Header and Data buffers Calculate
- *                                 Header Digest
- *      XMSTATE_BIT_CMD_HDR_XMIT - Transmit header in progress
- *
- *iscsi_send_padding
- *      XMSTATE_BIT_W_PAD        - Prepare and send pading
- *      XMSTATE_BIT_W_RESEND_PAD - retry send pading
- *
- *iscsi_send_digest
- *      XMSTATE_BIT_W_RESEND_DATA_DIGEST - Finalize and send Data Digest
- *      XMSTATE_BIT_W_RESEND_DATA_DIGEST - retry sending digest
- *
- *iscsi_send_unsol_hdr
- *      XMSTATE_BIT_UNS_INIT     - prepare un-solicit data header and digest
- *      XMSTATE_BIT_UNS_HDR      - send un-solicit header
- *
- *iscsi_send_unsol_pdu
- *      XMSTATE_BIT_UNS_DATA     - send un-solicit data in progress
- *
- *iscsi_send_sol_pdu
- *      XMSTATE_BIT_SOL_HDR_INIT - solicit data header and digest initialize
- *      XMSTATE_BIT_SOL_HDR      - send solicit header
- *      XMSTATE_BIT_SOL_DATA     - send solicit data
- *
- *iscsi_tcp_ctask_xmit
- *      XMSTATE_BIT_IMM_DATA     - xmit managment data (??)
- **/
-static int
-iscsi_tcp_ctask_xmit(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
-{
-        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
-        int rc = 0;
-
-        debug_scsi("ctask deq [cid %d xmstate %x itt 0x%x]\n",
-                conn->id, tcp_ctask->xmstate, ctask->itt);
-
-        rc = iscsi_send_cmd_hdr(conn, ctask);
-        if (rc)
-                return rc;
-        if (ctask->sc->sc_data_direction != DMA_TO_DEVICE)
-                return 0;
-
-        if (test_bit(XMSTATE_BIT_IMM_DATA, &tcp_ctask->xmstate)) {
-                rc = iscsi_send_data(ctask, &tcp_ctask->sendbuf, &tcp_ctask->sg,
-                                     &tcp_ctask->sent, &ctask->imm_count,
-                                     &tcp_ctask->immbuf, &tcp_ctask->immdigest);
-                if (rc)
-                        return rc;
-                clear_bit(XMSTATE_BIT_IMM_DATA, &tcp_ctask->xmstate);
-        }
-
-        rc = iscsi_send_unsol_pdu(conn, ctask);
-        if (rc)
-                return rc;
-
-        rc = iscsi_send_sol_pdu(conn, ctask);
-        if (rc)
-                return rc;
-
-        return rc;
+fail:
+        iscsi_conn_failure(conn, rc);
+        return -EIO;
 }
 
 static struct iscsi_cls_conn *
@@ -1784,9 +1492,6 @@ iscsi_tcp_conn_create(struct iscsi_cls_session *cls_session, uint32_t conn_idx)
 
         conn->dd_data = tcp_conn;
         tcp_conn->iscsi_conn = conn;
-        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
-        /* initial operational parameters */
-        tcp_conn->hdr_size = sizeof(struct iscsi_hdr);
 
         tcp_conn->tx_hash.tfm = crypto_alloc_hash("crc32c", 0,
                                                   CRYPTO_ALG_ASYNC);
@@ -1863,11 +1568,9 @@ static void
 iscsi_tcp_conn_stop(struct iscsi_cls_conn *cls_conn, int flag)
 {
         struct iscsi_conn *conn = cls_conn->dd_data;
-        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
 
         iscsi_conn_stop(cls_conn, flag);
         iscsi_tcp_release_conn(conn);
-        tcp_conn->hdr_size = sizeof(struct iscsi_hdr);
 }
 
 static int iscsi_tcp_get_addr(struct iscsi_conn *conn, struct socket *sock,
@@ -1967,7 +1670,7 @@ iscsi_tcp_conn_bind(struct iscsi_cls_session *cls_session,
         /*
          * set receive state machine into initial state
          */
-        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
+        iscsi_tcp_hdr_recv_prep(tcp_conn);
         return 0;
 
 free_socket:
@@ -1977,10 +1680,17 @@ free_socket:
 
 /* called with host lock */
 static void
-iscsi_tcp_mgmt_init(struct iscsi_conn *conn, struct iscsi_mgmt_task *mtask)
+iscsi_tcp_mtask_init(struct iscsi_conn *conn, struct iscsi_mgmt_task *mtask)
 {
-        struct iscsi_tcp_mgmt_task *tcp_mtask = mtask->dd_data;
-        tcp_mtask->xmstate = 1 << XMSTATE_BIT_IMM_HDR_INIT;
+        debug_scsi("mtask deq [cid %d itt 0x%x]\n", conn->id, mtask->itt);
+
+        /* Prepare PDU, optionally w/ immediate data */
+        iscsi_tcp_send_hdr_prep(conn, mtask->hdr, sizeof(*mtask->hdr));
+
+        /* If we have immediate data, attach a payload */
+        if (mtask->data_count)
+                iscsi_tcp_send_linear_data_prepare(conn, mtask->data,
+                                                   mtask->data_count);
 }
 
 static int
@@ -2003,8 +1713,7 @@ iscsi_r2tpool_alloc(struct iscsi_session *session)
                  */
 
                 /* R2T pool */
-                if (iscsi_pool_init(&tcp_ctask->r2tpool, session->max_r2t * 4,
-                                    (void***)&tcp_ctask->r2ts,
+                if (iscsi_pool_init(&tcp_ctask->r2tpool, session->max_r2t * 4, NULL,
                                     sizeof(struct iscsi_r2t_info))) {
                         goto r2t_alloc_fail;
                 }
@@ -2013,8 +1722,7 @@ iscsi_r2tpool_alloc(struct iscsi_session *session)
                 tcp_ctask->r2tqueue = kfifo_alloc(
                       session->max_r2t * 4 * sizeof(void*), GFP_KERNEL, NULL);
                 if (tcp_ctask->r2tqueue == ERR_PTR(-ENOMEM)) {
-                        iscsi_pool_free(&tcp_ctask->r2tpool,
-                                        (void**)tcp_ctask->r2ts);
+                        iscsi_pool_free(&tcp_ctask->r2tpool);
                         goto r2t_alloc_fail;
                 }
         }
@@ -2027,8 +1735,7 @@ r2t_alloc_fail:
                 struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
 
                 kfifo_free(tcp_ctask->r2tqueue);
-                iscsi_pool_free(&tcp_ctask->r2tpool,
-                                (void**)tcp_ctask->r2ts);
+                iscsi_pool_free(&tcp_ctask->r2tpool);
         }
         return -ENOMEM;
 }
@@ -2043,8 +1750,7 @@ iscsi_r2tpool_free(struct iscsi_session *session)
                 struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
 
                 kfifo_free(tcp_ctask->r2tqueue);
-                iscsi_pool_free(&tcp_ctask->r2tpool,
-                                (void**)tcp_ctask->r2ts);
+                iscsi_pool_free(&tcp_ctask->r2tpool);
         }
 }
 
@@ -2060,9 +1766,6 @@ iscsi_conn_set_param(struct iscsi_cls_conn *cls_conn, enum iscsi_param param,
         switch(param) {
         case ISCSI_PARAM_HDRDGST_EN:
                 iscsi_set_param(cls_conn, param, buf, buflen);
-                tcp_conn->hdr_size = sizeof(struct iscsi_hdr);
-                if (conn->hdrdgst_en)
-                        tcp_conn->hdr_size += sizeof(__u32);
                 break;
         case ISCSI_PARAM_DATADGST_EN:
                 iscsi_set_param(cls_conn, param, buf, buflen);
@@ -2071,12 +1774,12 @@ iscsi_conn_set_param(struct iscsi_cls_conn *cls_conn, enum iscsi_param param,
                 break;
         case ISCSI_PARAM_MAX_R2T:
                 sscanf(buf, "%d", &value);
-                if (session->max_r2t == roundup_pow_of_two(value))
+                if (value <= 0 || !is_power_of_2(value))
+                        return -EINVAL;
+                if (session->max_r2t == value)
                         break;
                 iscsi_r2tpool_free(session);
                 iscsi_set_param(cls_conn, param, buf, buflen);
-                if (session->max_r2t & (session->max_r2t - 1))
-                        session->max_r2t = roundup_pow_of_two(session->max_r2t);
                 if (iscsi_r2tpool_alloc(session))
                         return -ENOMEM;
                 break;
@@ -2183,14 +1886,15 @@ iscsi_tcp_session_create(struct iscsi_transport *iscsit,
                 struct iscsi_cmd_task *ctask = session->cmds[cmd_i];
                 struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
 
-                ctask->hdr = &tcp_ctask->hdr;
+                ctask->hdr = &tcp_ctask->hdr.cmd_hdr;
+                ctask->hdr_max = sizeof(tcp_ctask->hdr) - ISCSI_DIGEST_SIZE;
         }
 
         for (cmd_i = 0; cmd_i < session->mgmtpool_max; cmd_i++) {
                 struct iscsi_mgmt_task *mtask = session->mgmt_cmds[cmd_i];
                 struct iscsi_tcp_mgmt_task *tcp_mtask = mtask->dd_data;
 
-                mtask->hdr = &tcp_mtask->hdr;
+                mtask->hdr = (struct iscsi_hdr *) &tcp_mtask->hdr;
         }
 
         if (iscsi_r2tpool_alloc(class_to_transport_session(cls_session)))
@@ -2222,12 +1926,14 @@ static struct scsi_host_template iscsi_sht = {
         .queuecommand           = iscsi_queuecommand,
         .change_queue_depth     = iscsi_change_queue_depth,
         .can_queue              = ISCSI_DEF_XMIT_CMDS_MAX - 1,
-        .sg_tablesize           = ISCSI_SG_TABLESIZE,
+        .sg_tablesize           = 4096,
         .max_sectors            = 0xFFFF,
         .cmd_per_lun            = ISCSI_DEF_CMD_PER_LUN,
         .eh_abort_handler       = iscsi_eh_abort,
+        .eh_device_reset_handler= iscsi_eh_device_reset,
         .eh_host_reset_handler  = iscsi_eh_host_reset,
         .use_clustering         = DISABLE_CLUSTERING,
+        .use_sg_chaining        = ENABLE_SG_CHAINING,
         .slave_configure        = iscsi_tcp_slave_configure,
         .proc_name              = "iscsi_tcp",
         .this_id                = -1,
@@ -2257,14 +1963,17 @@ static struct iscsi_transport iscsi_tcp_transport = {
                                   ISCSI_PERSISTENT_ADDRESS |
                                   ISCSI_TARGET_NAME | ISCSI_TPGT |
                                   ISCSI_USERNAME | ISCSI_PASSWORD |
-                                  ISCSI_USERNAME_IN | ISCSI_PASSWORD_IN,
+                                  ISCSI_USERNAME_IN | ISCSI_PASSWORD_IN |
+                                  ISCSI_FAST_ABORT | ISCSI_ABORT_TMO |
+                                  ISCSI_LU_RESET_TMO |
+                                  ISCSI_PING_TMO | ISCSI_RECV_TMO,
         .host_param_mask        = ISCSI_HOST_HWADDRESS | ISCSI_HOST_IPADDRESS |
                                   ISCSI_HOST_INITIATOR_NAME |
                                   ISCSI_HOST_NETDEV_NAME,
         .host_template          = &iscsi_sht,
         .conndata_size          = sizeof(struct iscsi_conn),
         .max_conn               = 1,
-        .max_cmd_len            = ISCSI_TCP_MAX_CMD_LEN,
+        .max_cmd_len            = 16,
         /* session management */
         .create_session         = iscsi_tcp_session_create,
         .destroy_session        = iscsi_tcp_session_destroy,
@@ -2283,8 +1992,8 @@ static struct iscsi_transport iscsi_tcp_transport = {
         /* IO */
         .send_pdu               = iscsi_conn_send_pdu,
         .get_stats              = iscsi_conn_get_stats,
-        .init_cmd_task          = iscsi_tcp_cmd_init,
-        .init_mgmt_task         = iscsi_tcp_mgmt_init,
+        .init_cmd_task          = iscsi_tcp_ctask_init,
+        .init_mgmt_task         = iscsi_tcp_mtask_init,
         .xmit_cmd_task          = iscsi_tcp_ctask_xmit,
         .xmit_mgmt_task         = iscsi_tcp_mtask_xmit,
         .cleanup_cmd_task       = iscsi_tcp_cleanup_ctask,