[SCSI] iscsi_tcp: rewrite recv path

Rewrite recv path. Fixes:
- data digest processing and error handling.
- ahs support.

Some fixups by Mike Christie

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

3 files changed, 552 insertions, 536 deletions

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 4b226b88b68a..1b540e03f5bf 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
@@ -67,10 +67,15 @@ 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_chunk *chunk);
+
 static inline void
 iscsi_buf_init_iov(struct iscsi_buf *ibuf, char *vbuf, int size)
 {
-        sg_init_one(&ibuf->sg, vbuf, size);
+        ibuf->sg.page = virt_to_page(vbuf);
+        ibuf->sg.offset = offset_in_page(vbuf);
+        ibuf->sg.length = size;
         ibuf->sent = 0;
         ibuf->use_sendmsg = 1;
 }
@@ -78,12 +83,13 @@ iscsi_buf_init_iov(struct iscsi_buf *ibuf, char *vbuf, int size)
 static inline void
 iscsi_buf_init_sg(struct iscsi_buf *ibuf, struct scatterlist *sg)
 {
-        sg_init_table(&ibuf->sg, 1);
-        sg_set_page(&ibuf->sg, sg_page(sg), sg->length, sg->offset);
+        ibuf->sg.page = sg->page;
+        ibuf->sg.offset = sg->offset;
+        ibuf->sg.length = sg->length;
         /*
          * Fastpath: sg element fits into single page
          */
-        if (sg->length + sg->offset <= PAGE_SIZE && !PageSlab(sg_page(sg)))
+        if (sg->length + sg->offset <= PAGE_SIZE && !PageSlab(sg->page))
                 ibuf->use_sendmsg = 0;
         else
                 ibuf->use_sendmsg = 1;
@@ -110,72 +116,331 @@ iscsi_hdr_digest(struct iscsi_conn *conn, struct iscsi_buf *buf,
         buf->sg.length += sizeof(u32);
 }
 
+/*
+ * Scatterlist handling: inside the iscsi_chunk, 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_chunk_init_sg - init indicated scatterlist entry
+ * @chunk: the buffer object
+ * @idx: index into scatterlist
+ * @offset: byte offset into that sg entry
+ *
+ * This function sets up the chunk so that subsequent
+ * data is copied to the indicated sg entry, at the given
+ * offset.
+ */
+static inline void
+iscsi_tcp_chunk_init_sg(struct iscsi_chunk *chunk,
+                        unsigned int idx, unsigned int offset)
+{
+        struct scatterlist *sg;
+
+        BUG_ON(chunk->sg == NULL);
+
+        sg = &chunk->sg[idx];
+        chunk->sg_index = idx;
+        chunk->sg_offset = offset;
+        chunk->size = min(sg->length - offset, chunk->total_size);
+        chunk->data = NULL;
+}
+
+/**
+ * iscsi_tcp_chunk_map - map the current S/G page
+ * @chunk: iscsi chunk
+ *
+ * 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_tcp_chunk_map(struct iscsi_chunk *chunk)
+{
+        struct scatterlist *sg;
+
+        if (chunk->data != NULL || !chunk->sg)
+                return;
+
+        sg = &chunk->sg[chunk->sg_index];
+        BUG_ON(chunk->sg_mapped);
+        BUG_ON(sg->length == 0);
+        chunk->sg_mapped = kmap_atomic(sg->page, KM_SOFTIRQ0);
+        chunk->data = chunk->sg_mapped + sg->offset + chunk->sg_offset;
+}
+
+static inline void
+iscsi_tcp_chunk_unmap(struct iscsi_chunk *chunk)
+{
+        if (chunk->sg_mapped) {
+                kunmap_atomic(chunk->sg_mapped, KM_SOFTIRQ0);
+                chunk->sg_mapped = NULL;
+                chunk->data = NULL;
+        }
+}
+
+/*
+ * Splice the digest buffer into the buffer
+ */
+static inline void
+iscsi_tcp_chunk_splice_digest(struct iscsi_chunk *chunk, void *digest)
+{
+        chunk->data = digest;
+        chunk->digest_len = ISCSI_DIGEST_SIZE;
+        chunk->total_size += ISCSI_DIGEST_SIZE;
+        chunk->size = ISCSI_DIGEST_SIZE;
+        chunk->copied = 0;
+        chunk->sg = NULL;
+        chunk->sg_index = 0;
+        chunk->hash = NULL;
+}
+
+/**
+ * iscsi_tcp_chunk_done - check whether the chunk is complete
+ * @chunk: iscsi chunk to check
+ *
+ * Check if we're done receiving this chunk. 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_chunk_done(struct iscsi_chunk *chunk)
 {
-        struct sk_buff *skb = tcp_conn->in.skb;
+        static unsigned char padbuf[ISCSI_PAD_LEN];
+
+        if (chunk->copied < chunk->size) {
+                iscsi_tcp_chunk_map(chunk);
+                return 0;
+        }
 
-        tcp_conn->in.zero_copy_hdr = 0;
+        chunk->total_copied += chunk->copied;
+        chunk->copied = 0;
+        chunk->size = 0;
 
-        if (tcp_conn->in.copy >= tcp_conn->hdr_size &&
-            tcp_conn->in_progress == IN_PROGRESS_WAIT_HEADER) {
-                /*
-                 * Zero-copy PDU Header: using connection context
-                 * to store header pointer.
-                 */
-                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;
-                } 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;
+        /* Unmap the current scatterlist page, if there is one. */
+        iscsi_tcp_chunk_unmap(chunk);
+
+        /* Do we have more scatterlist entries? */
+        if (chunk->total_copied < chunk->total_size) {
+                /* Proceed to the next entry in the scatterlist. */
+                iscsi_tcp_chunk_init_sg(chunk, chunk->sg_index + 1, 0);
+                iscsi_tcp_chunk_map(chunk);
+                BUG_ON(chunk->size == 0);
+                return 0;
+        }
+
+        /* Do we need to handle padding? */
+        if (chunk->total_copied & (ISCSI_PAD_LEN-1)) {
+                unsigned int pad;
+
+                pad = ISCSI_PAD_LEN - (chunk->total_copied & (ISCSI_PAD_LEN-1));
+                debug_tcp("consume %d pad bytes\n", pad);
+                chunk->total_size += pad;
+                chunk->size = pad;
+                chunk->data = padbuf;
+                return 0;
+        }
+
+        /*
+         * Set us up for receiving the data digest. hdr digest
+         * is completely handled in hdr done function.
+         */
+        if (chunk->hash) {
+                if (chunk->digest_len == 0) {
+                        crypto_hash_final(chunk->hash, chunk->digest);
+                        iscsi_tcp_chunk_splice_digest(chunk,
+                                                      chunk->recv_digest);
+                        return 0;
                 }
-                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.
-                 */
+        return 1;
+}
+
+/**
+ * iscsi_tcp_chunk_recv - copy data to chunk
+ * @tcp_conn: the iSCSI TCP connection
+ * @chunk: 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_chunk_recv(struct iscsi_tcp_conn *tcp_conn,
+                     struct iscsi_chunk *chunk, const void *ptr,
+                     unsigned int len)
+{
+        struct scatterlist sg;
+        unsigned int copy, copied = 0;
+
+        while (!iscsi_tcp_chunk_done(chunk)) {
+                if (copied == len)
+                        goto out;
+
+                copy = min(len - copied, chunk->size - chunk->copied);
+                memcpy(chunk->data + chunk->copied, ptr + copied, copy);
+
+                if (chunk->hash) {
+                        sg_init_one(&sg, ptr + copied, copy);
+                        crypto_hash_update(chunk->hash, &sg, copy);
+                }
+                chunk->copied += copy;
+                copied += copy;
+        }
+
+out:
+        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;
+
+        sg_init_one(&sg, hdr, hdrlen);
+        crypto_hash_digest(hash, &sg, hdrlen, digest);
+}
+
+static inline int
+iscsi_tcp_dgst_verify(struct iscsi_tcp_conn *tcp_conn,
+                      struct iscsi_chunk *chunk)
+{
+        if (!chunk->digest_len)
+                return 1;
+
+        if (memcmp(chunk->recv_digest, chunk->digest, chunk->digest_len)) {
+                debug_scsi("digest mismatch\n");
+                return 0;
+        }
 
-                hdr_remains = tcp_conn->hdr_size - tcp_conn->in.hdr_offset;
-                BUG_ON(hdr_remains <= 0);
+        return 1;
+}
 
-                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);
+/*
+ * Helper function to set up chunk buffer
+ */
+static inline void
+__iscsi_chunk_init(struct iscsi_chunk *chunk, size_t size,
+                   iscsi_chunk_done_fn_t *done, struct hash_desc *hash)
+{
+        memset(chunk, 0, sizeof(*chunk));
+        chunk->total_size = size;
+        chunk->done = done;
 
-                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 (hash) {
+                chunk->hash = hash;
+                crypto_hash_init(hash);
+        }
+}
 
-                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;
+static inline void
+iscsi_chunk_init_linear(struct iscsi_chunk *chunk, void *data, size_t size,
+                        iscsi_chunk_done_fn_t *done, struct hash_desc *hash)
+{
+        __iscsi_chunk_init(chunk, size, done, hash);
+        chunk->data = data;
+        chunk->size = size;
+}
+
+static inline int
+iscsi_chunk_seek_sg(struct iscsi_chunk *chunk,
+                    struct scatterlist *sg, unsigned int sg_count,
+                    unsigned int offset, size_t size,
+                    iscsi_chunk_done_fn_t *done, struct hash_desc *hash)
+{
+        unsigned int i;
+
+        __iscsi_chunk_init(chunk, size, done, hash);
+        for (i = 0; i < sg_count; ++i) {
+                if (offset < sg[i].length) {
+                        chunk->sg = sg;
+                        chunk->sg_count = sg_count;
+                        iscsi_tcp_chunk_init_sg(chunk, i, 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[i].length;
         }
 
+        return ISCSI_ERR_DATA_OFFSET;
+}
+
+/**
+ * iscsi_tcp_hdr_recv_prep - prep chunk 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_chunk_init_linear(&tcp_conn->in.chunk,
+                                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_chunk *chunk)
+{
+        struct iscsi_conn *conn = tcp_conn->iscsi_conn;
+        int rc = 0;
+
+        if (!iscsi_tcp_dgst_verify(tcp_conn, chunk))
+                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_chunk_init_linear(&tcp_conn->in.chunk,
+                                conn->data, tcp_conn->in.datalen,
+                                iscsi_tcp_data_recv_done, rx_hash);
+}
+
 /*
  * must be called with session lock
  */
@@ -417,16 +682,49 @@ iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *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_chunk *chunk)
+{
+        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, chunk))
+                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);
@@ -435,77 +733,72 @@ 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) {
+                /* XXX: what does this do? */
                 tcp_conn->in.datalen = 0; /* force drop */
                 return 0;
         } else 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];
+                rc = iscsi_data_rsp(conn, ctask);
                 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_chunk 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_chunk_seek_sg(&tcp_conn->in.chunk,
+                                                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 if (ctask->sc->sc_data_direction == DMA_TO_DEVICE)
+                        rc = iscsi_r2t_rsp(conn, ctask);
                 else
                         rc = ISCSI_ERR_PROTO;
                 break;
@@ -518,8 +811,7 @@ 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,
@@ -528,8 +820,13 @@ 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:
@@ -541,129 +838,15 @@ 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;
-}
-
-/**
- * iscsi_tcp_copy - copy skb bits to the destanation buffer
- * @conn: iscsi tcp connection
- *
- * 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;
+        return rc;
 }
 
 static inline void
@@ -677,325 +860,146 @@ partial_sg_digest_update(struct hash_desc *desc, struct scatterlist *sg,
         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)
+/**
+ * iscsi_tcp_hdr_recv_done - process PDU header
+ *
+ * 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_chunk *chunk)
 {
-        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 (chunk->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;
+
+                chunk->total_size += ahslen;
+                chunk->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 (chunk->digest_len == 0) {
+                        iscsi_tcp_chunk_splice_digest(chunk,
+                                                      chunk->recv_digest);
+                        return 0;
                 }
+                iscsi_tcp_dgst_header(&tcp_conn->rx_hash, hdr,
+                                      chunk->total_copied - ISCSI_DIGEST_SIZE,
+                                      chunk->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, chunk))
+                        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_chunk *chunk = &tcp_conn->in.chunk;
+        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;
-                       }
-                }
-
-                /*
-                 * 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;
-                }
-        }
-
-        if (tcp_conn->in_progress == IN_PROGRESS_DDIGEST_RECV &&
-            tcp_conn->in.copy) {
-                uint32_t recv_digest;
+        skb_prepare_seq_read(skb, offset, skb->len, &seq);
+        while (1) {
+                unsigned int avail;
+                const u8 *ptr;
 
-                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);
+                avail = skb_seq_read(consumed, &ptr, &seq);
+                if (avail == 0)
+                        break;
+                BUG_ON(chunk->copied >= chunk->size);
+
+                debug_tcp("skb %p ptr=%p avail=%u\n", skb, ptr, avail);
+                rc = iscsi_tcp_chunk_recv(tcp_conn, chunk, ptr, avail);
+                BUG_ON(rc == 0);
+                consumed += rc;
+
+                if (chunk->total_copied >= chunk->total_size) {
+                        rc = chunk->done(tcp_conn, chunk);
+                        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;
-                }
-        }
-
-        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;
+                        /* The done() functions sets up the
+                         * next chunk. */
                 }
-
-                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);
+        conn->rxdata_octets += consumed;
+        return consumed;
 
-        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_chunk_unmap(&tcp_conn->in.chunk);
 }
 
 static void
@@ -1097,9 +1101,9 @@ iscsi_send(struct iscsi_conn *conn, struct iscsi_buf *buf, int size, int flags)
          * slab case.
          */
         if (buf->use_sendmsg)
-                res = sock_no_sendpage(sk, sg_page(&buf->sg), offset, size, flags);
+                res = sock_no_sendpage(sk, buf->sg.page, offset, size, flags);
         else
-                res = tcp_conn->sendpage(sk, sg_page(&buf->sg), offset, size, flags);
+                res = tcp_conn->sendpage(sk, buf->sg.page, offset, size, flags);
 
         if (res >= 0) {
                 conn->txdata_octets += res;
@@ -1783,9 +1787,6 @@ 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);
@@ -1862,11 +1863,9 @@ 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,
@@ -1966,7 +1965,7 @@ 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:
@@ -2059,9 +2058,6 @@ 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);
diff --git a/drivers/scsi/iscsi_tcp.h b/drivers/scsi/iscsi_tcp.h
index 7eba44df0a7f..f1c541151100 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -24,13 +24,6 @@
 
 #include <scsi/libiscsi.h>
 
-/* Socket's Receive state machine */
-#define IN_PROGRESS_WAIT_HEADER         0x0
-#define IN_PROGRESS_HEADER_GATHER       0x1
-#define IN_PROGRESS_DATA_RECV           0x2
-#define IN_PROGRESS_DDIGEST_RECV        0x3
-#define IN_PROGRESS_PAD_RECV            0x4
-
 /* xmit state machine */
 #define XMSTATE_IDLE                    0x0
 #define XMSTATE_CMD_HDR_INIT            0x1
@@ -54,41 +47,64 @@
 
 struct crypto_hash;
 struct socket;
+struct iscsi_tcp_conn;
+struct iscsi_chunk;
+
+typedef int iscsi_chunk_done_fn_t(struct iscsi_tcp_conn *,
+                                  struct iscsi_chunk *);
+
+struct iscsi_chunk {
+        unsigned char           *data;
+        unsigned int            size;
+        unsigned int            copied;
+        unsigned int            total_size;
+        unsigned int            total_copied;
+
+        struct hash_desc        *hash;
+        unsigned char           recv_digest[ISCSI_DIGEST_SIZE];
+        unsigned char           digest[ISCSI_DIGEST_SIZE];
+        unsigned int            digest_len;
+
+        struct scatterlist      *sg;
+        void                    *sg_mapped;
+        unsigned int            sg_offset;
+        unsigned int            sg_index;
+        unsigned int            sg_count;
+
+        iscsi_chunk_done_fn_t   *done;
+};
 
 /* Socket connection recieve helper */
 struct iscsi_tcp_recv {
         struct iscsi_hdr        *hdr;
-        struct sk_buff          *skb;
-        int                     offset;
-        int                     len;
-        int                     hdr_offset;
-        int                     copy;
-        int                     copied;
-        int                     padding;
-        struct iscsi_cmd_task   *ctask;         /* current cmd in progress */
+        struct iscsi_chunk      chunk;
+
+        /* Allocate buffer for BHS + AHS */
+        uint32_t                hdr_buf[64];
 
         /* copied and flipped values */
         int                     datalen;
-        int                     datadgst;
-        char                    zero_copy_hdr;
+};
+
+/* Socket connection send helper */
+struct iscsi_tcp_send {
+        struct iscsi_hdr        *hdr;
+        struct iscsi_chunk      chunk;
+        struct iscsi_chunk      data_chunk;
+
+        /* Allocate buffer for BHS + AHS */
+        uint32_t                hdr_buf[64];
 };
 
 struct iscsi_tcp_conn {
         struct iscsi_conn       *iscsi_conn;
         struct socket           *sock;
-        struct iscsi_hdr        hdr;            /* header placeholder */
-        char                    hdrext[4*sizeof(__u16) +
-                                    sizeof(__u32)];
-        int                     data_copied;
         int                     stop_stage;     /* conn_stop() flag: *
                                                  * stop to recover,  *
                                                  * stop to terminate */
-        /* iSCSI connection-wide sequencing */
-        int                     hdr_size;       /* PDU header size */
-
         /* control data */
         struct iscsi_tcp_recv   in;             /* TCP receive context */
-        int                     in_progress;    /* connection state machine */
+        struct iscsi_tcp_send   out;            /* TCP send context */
 
         /* old values for socket callbacks */
         void                    (*old_data_ready)(struct sock *, int);
diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index 89429f433f85..e1fb3d0927b0 100644
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -77,6 +77,10 @@ enum {
 
 #define ISCSI_ADDRESS_BUF_LEN           64
 
+enum {
+        ISCSI_DIGEST_SIZE = sizeof(__u32),
+};
+
 struct iscsi_mgmt_task {
         /*
          * Becuae LLDs allocate their hdr differently, this is a pointer to