[SCSI] iscsi: fix writepsace race

We can race and misset the suspend bit if iscsi_write_space is
called then iscsi_send returns with a failure indicating
there is no space.

To handle this this patch returns a error upwards allowing xmitworker
to decide if we need to try and transmit again. For the no
write space case xmitworker will not retry, and instead
let iscsi_write_space queue it back up if needed (this relies
on the work queue code to properly requeue us if needed).

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

3 files changed, 126 insertions, 95 deletions

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 2abda804a924..7fa85937a99f 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -1006,7 +1006,6 @@ iscsi_write_space(struct sock *sk)
 
         tcp_conn->old_write_space(sk);
         debug_tcp("iscsi_write_space: cid %d\n", conn->id);
-        clear_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx);
         scsi_queue_work(conn->session->host, &conn->xmitwork);
 }
 
@@ -1056,7 +1055,7 @@ iscsi_send(struct iscsi_conn *conn, struct iscsi_buf *buf, int size, int flags)
 {
         struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
         struct socket *sk = tcp_conn->sock;
-        int offset = buf->sg.offset + buf->sent;
+        int offset = buf->sg.offset + buf->sent, res;
 
         /*
          * if we got use_sg=0 or are sending something we kmallocd
@@ -1067,10 +1066,22 @@ iscsi_send(struct iscsi_conn *conn, struct iscsi_buf *buf, int size, int flags)
          * slab case.
          */
         if (buf->use_sendmsg)
-                return sock_no_sendpage(sk, buf->sg.page, offset, size, flags);
+                res = sock_no_sendpage(sk, buf->sg.page, offset, size, flags);
         else
-                return tcp_conn->sendpage(sk, buf->sg.page, offset, size,
-                                          flags);
+                res = tcp_conn->sendpage(sk, buf->sg.page, offset, size, flags);
+
+        if (res >= 0) {
+                conn->txdata_octets += res;
+                buf->sent += res;
+                return res;
+        }
+
+        tcp_conn->sendpage_failures_cnt++;
+        if (res == -EAGAIN)
+                res = -ENOBUFS;
+        else
+                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
+        return res;
 }
 
 /**
@@ -1085,7 +1096,6 @@ iscsi_send(struct iscsi_conn *conn, struct iscsi_buf *buf, int size, int flags)
 static inline int
 iscsi_sendhdr(struct iscsi_conn *conn, struct iscsi_buf *buf, int datalen)
 {
-        struct iscsi_tcp_conn *tcp_conn;
         int flags = 0; /* MSG_DONTWAIT; */
         int res, size;
 
@@ -1097,17 +1107,10 @@ iscsi_sendhdr(struct iscsi_conn *conn, struct iscsi_buf *buf, int datalen)
         res = iscsi_send(conn, buf, size, flags);
         debug_tcp("sendhdr %d bytes, sent %d res %d\n", size, buf->sent, res);
         if (res >= 0) {
-                conn->txdata_octets += res;
-                buf->sent += res;
                 if (size != res)
                         return -EAGAIN;
                 return 0;
-        } else if (res == -EAGAIN) {
-                tcp_conn = conn->dd_data;
-                tcp_conn->sendpage_failures_cnt++;
-                set_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx);
-        } else if (res == -EPIPE)
-                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
+        }
 
         return res;
 }
@@ -1126,7 +1129,6 @@ static inline int
 iscsi_sendpage(struct iscsi_conn *conn, struct iscsi_buf *buf,
                int *count, int *sent)
 {
-        struct iscsi_tcp_conn *tcp_conn;
         int flags = 0; /* MSG_DONTWAIT; */
         int res, size;
 
@@ -1141,19 +1143,12 @@ iscsi_sendpage(struct iscsi_conn *conn, struct iscsi_buf *buf,
         debug_tcp("sendpage: %d bytes, sent %d left %d sent %d res %d\n",
                   size, buf->sent, *count, *sent, res);
         if (res >= 0) {
-                conn->txdata_octets += res;
-                buf->sent += res;
                 *count -= res;
                 *sent += res;
                 if (size != res)
                         return -EAGAIN;
                 return 0;
-        } else if (res == -EAGAIN) {
-                tcp_conn = conn->dd_data;
-                tcp_conn->sendpage_failures_cnt++;
-                set_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx);
-        } else if (res == -EPIPE)
-                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
+        }
 
         return res;
 }
@@ -1342,6 +1337,7 @@ 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);
@@ -1355,12 +1351,13 @@ iscsi_tcp_mtask_xmit(struct iscsi_conn *conn, struct iscsi_mgmt_task *mtask)
                     conn->hdrdgst_en)
                         iscsi_hdr_digest(conn, &tcp_mtask->headbuf,
                                         (u8*)tcp_mtask->hdrext);
-                if (iscsi_sendhdr(conn, &tcp_mtask->headbuf,
-                                  mtask->data_count)) {
+                rc = iscsi_sendhdr(conn, &tcp_mtask->headbuf,
+                                   mtask->data_count);
+                if (rc) {
                         tcp_mtask->xmstate |= XMSTATE_IMM_HDR;
                         if (mtask->data_count)
                                 tcp_mtask->xmstate &= ~XMSTATE_IMM_DATA;
-                        return -EAGAIN;
+                        return rc;
                 }
         }
 
@@ -1371,10 +1368,13 @@ iscsi_tcp_mtask_xmit(struct iscsi_conn *conn, struct iscsi_mgmt_task *mtask)
                  * Virtual buffer could be spreaded across multiple pages...
                  */
                 do {
-                        if (iscsi_sendpage(conn, &tcp_mtask->sendbuf,
-                                   &mtask->data_count, &tcp_mtask->sent)) {
+                        int rc;
+
+                        rc = iscsi_sendpage(conn, &tcp_mtask->sendbuf,
+                                        &mtask->data_count, &tcp_mtask->sent);
+                        if (rc) {
                                 tcp_mtask->xmstate |= XMSTATE_IMM_DATA;
-                                return -EAGAIN;
+                                return rc;
                         }
                 } while (mtask->data_count);
         }
@@ -1396,16 +1396,19 @@ static inline int
 handle_xmstate_r_hdr(struct iscsi_conn *conn,
                      struct iscsi_tcp_cmd_task *tcp_ctask)
 {
+        int rc;
+
         tcp_ctask->xmstate &= ~XMSTATE_R_HDR;
         if (conn->hdrdgst_en)
                 iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
                                  (u8*)tcp_ctask->hdrext);
-        if (!iscsi_sendhdr(conn, &tcp_ctask->headbuf, 0)) {
+        rc = iscsi_sendhdr(conn, &tcp_ctask->headbuf, 0);
+        if (!rc) {
                 BUG_ON(tcp_ctask->xmstate != XMSTATE_IDLE);
                 return 0; /* wait for Data-In */
         }
         tcp_ctask->xmstate |= XMSTATE_R_HDR;
-        return -EAGAIN;
+        return rc;
 }
 
 static inline int
@@ -1413,16 +1416,16 @@ handle_xmstate_w_hdr(struct iscsi_conn *conn,
                      struct iscsi_cmd_task *ctask)
 {
         struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
+        int rc;
 
         tcp_ctask->xmstate &= ~XMSTATE_W_HDR;
         if (conn->hdrdgst_en)
                 iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
                                  (u8*)tcp_ctask->hdrext);
-        if (iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->imm_count)) {
+        rc = iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->imm_count);
+        if (rc)
                 tcp_ctask->xmstate |= XMSTATE_W_HDR;
-                return -EAGAIN;
-        }
-        return 0;
+        return rc;
 }
 
 static inline int
@@ -1430,17 +1433,19 @@ handle_xmstate_data_digest(struct iscsi_conn *conn,
                            struct iscsi_cmd_task *ctask)
 {
         struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
+        int rc;
 
         tcp_ctask->xmstate &= ~XMSTATE_DATA_DIGEST;
         debug_tcp("resent data digest 0x%x\n", tcp_ctask->datadigest);
-        if (iscsi_digest_final_send(conn, ctask, &tcp_ctask->immbuf,
-                                    &tcp_ctask->datadigest, 0)) {
+        rc = iscsi_digest_final_send(conn, ctask, &tcp_ctask->immbuf,
+                                    &tcp_ctask->datadigest, 0);
+        if (rc) {
                 tcp_ctask->xmstate |= XMSTATE_DATA_DIGEST;
                 debug_tcp("resent data digest 0x%x fail!\n",
                           tcp_ctask->datadigest);
-                return -EAGAIN;
         }
-        return 0;
+
+        return rc;
 }
 
 static inline int
@@ -1448,6 +1453,7 @@ handle_xmstate_imm_data(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 rc;
 
         BUG_ON(!ctask->imm_count);
         tcp_ctask->xmstate &= ~XMSTATE_IMM_DATA;
@@ -1458,8 +1464,9 @@ handle_xmstate_imm_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         }
 
         for (;;) {
-                if (iscsi_sendpage(conn, &tcp_ctask->sendbuf, &ctask->imm_count,
-                                   &tcp_ctask->sent)) {
+                rc = iscsi_sendpage(conn, &tcp_ctask->sendbuf,
+                                   &ctask->imm_count, &tcp_ctask->sent);
+                if (rc) {
                         tcp_ctask->xmstate |= XMSTATE_IMM_DATA;
                         if (conn->datadgst_en) {
                                 crypto_digest_final(tcp_conn->data_tx_tfm,
@@ -1467,7 +1474,7 @@ handle_xmstate_imm_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
                                 debug_tcp("tx imm sendpage fail 0x%x\n",
                                           tcp_ctask->datadigest);
                         }
-                        return -EAGAIN;
+                        return rc;
                 }
                 if (conn->datadgst_en)
                         crypto_digest_update(tcp_conn->data_tx_tfm,
@@ -1480,11 +1487,12 @@ handle_xmstate_imm_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         }
 
         if (conn->datadgst_en && !(tcp_ctask->xmstate & XMSTATE_W_PAD)) {
-                if (iscsi_digest_final_send(conn, ctask, &tcp_ctask->immbuf,
-                                            &tcp_ctask->immdigest, 1)) {
+                rc = iscsi_digest_final_send(conn, ctask, &tcp_ctask->immbuf,
+                                            &tcp_ctask->immdigest, 1);
+                if (rc) {
                         debug_tcp("sending imm digest 0x%x fail!\n",
                                   tcp_ctask->immdigest);
-                        return -EAGAIN;
+                        return rc;
                 }
                 debug_tcp("sending imm digest 0x%x\n", tcp_ctask->immdigest);
         }
@@ -1497,6 +1505,7 @@ handle_xmstate_uns_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;
 
         tcp_ctask->xmstate |= XMSTATE_UNS_DATA;
         if (tcp_ctask->xmstate & XMSTATE_UNS_INIT) {
@@ -1507,10 +1516,12 @@ handle_xmstate_uns_hdr(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
                                         (u8*)dtask->hdrext);
                 tcp_ctask->xmstate &= ~XMSTATE_UNS_INIT;
         }
-        if (iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->data_count)) {
+
+        rc = iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->data_count);
+        if (rc) {
                 tcp_ctask->xmstate &= ~XMSTATE_UNS_DATA;
                 tcp_ctask->xmstate |= XMSTATE_UNS_HDR;
-                return -EAGAIN;
+                return rc;
         }
 
         debug_scsi("uns dout [itt 0x%x dlen %d sent %d]\n",
@@ -1524,6 +1535,7 @@ handle_xmstate_uns_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
         struct iscsi_data_task *dtask = tcp_ctask->dtask;
         struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
+        int rc;
 
         BUG_ON(!ctask->data_count);
         tcp_ctask->xmstate &= ~XMSTATE_UNS_DATA;
@@ -1536,8 +1548,9 @@ handle_xmstate_uns_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         for (;;) {
                 int start = tcp_ctask->sent;
 
-                if (iscsi_sendpage(conn, &tcp_ctask->sendbuf,
-                                   &ctask->data_count, &tcp_ctask->sent)) {
+                rc = iscsi_sendpage(conn, &tcp_ctask->sendbuf,
+                                   &ctask->data_count, &tcp_ctask->sent);
+                if (rc) {
                         ctask->unsol_count -= tcp_ctask->sent - start;
                         tcp_ctask->xmstate |= XMSTATE_UNS_DATA;
                         /* will continue with this ctask later.. */
@@ -1547,7 +1560,7 @@ handle_xmstate_uns_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
                                 debug_tcp("tx uns data fail 0x%x\n",
                                           dtask->digest);
                         }
-                        return -EAGAIN;
+                        return rc;
                 }
 
                 BUG_ON(tcp_ctask->sent > ctask->total_length);
@@ -1574,12 +1587,13 @@ handle_xmstate_uns_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
          */
         if (ctask->unsol_count) {
                 if (conn->datadgst_en) {
-                        if (iscsi_digest_final_send(conn, ctask,
+                        rc = iscsi_digest_final_send(conn, ctask,
                                                     &dtask->digestbuf,
-                                                    &dtask->digest, 1)) {
+                                                    &dtask->digest, 1);
+                        if (rc) {
                                 debug_tcp("send uns digest 0x%x fail\n",
                                           dtask->digest);
-                                return -EAGAIN;
+                                return rc;
                         }
                         debug_tcp("sending uns digest 0x%x, more uns\n",
                                   dtask->digest);
@@ -1589,12 +1603,13 @@ handle_xmstate_uns_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         }
 
         if (conn->datadgst_en && !(tcp_ctask->xmstate & XMSTATE_W_PAD)) {
-                if (iscsi_digest_final_send(conn, ctask,
+                rc = iscsi_digest_final_send(conn, ctask,
                                             &dtask->digestbuf,
-                                            &dtask->digest, 1)) {
+                                            &dtask->digest, 1);
+                if (rc) {
                         debug_tcp("send last uns digest 0x%x fail\n",
                                    dtask->digest);
-                        return -EAGAIN;
+                        return rc;
                 }
                 debug_tcp("sending uns digest 0x%x\n",dtask->digest);
         }
@@ -1610,7 +1625,7 @@ handle_xmstate_sol_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
         struct iscsi_r2t_info *r2t = tcp_ctask->r2t;
         struct iscsi_data_task *dtask = &r2t->dtask;
-        int left;
+        int left, rc;
 
         tcp_ctask->xmstate &= ~XMSTATE_SOL_DATA;
         tcp_ctask->dtask = dtask;
@@ -1626,7 +1641,8 @@ solicit_again:
         if (!r2t->data_count)
                 goto data_out_done;
 
-        if (iscsi_sendpage(conn, &r2t->sendbuf, &r2t->data_count, &r2t->sent)) {
+        rc = iscsi_sendpage(conn, &r2t->sendbuf, &r2t->data_count, &r2t->sent);
+        if (rc) {
                 tcp_ctask->xmstate |= XMSTATE_SOL_DATA;
                 /* will continue with this ctask later.. */
                 if (conn->datadgst_en) {
@@ -1634,7 +1650,7 @@ solicit_again:
                                           (u8 *)&dtask->digest);
                         debug_tcp("r2t data send fail 0x%x\n", dtask->digest);
                 }
-                return -EAGAIN;
+                return rc;
         }
 
         BUG_ON(r2t->data_count < 0);
@@ -1661,12 +1677,13 @@ data_out_done:
         left = r2t->data_length - r2t->sent;
         if (left) {
                 if (conn->datadgst_en) {
-                        if (iscsi_digest_final_send(conn, ctask,
+                        rc = iscsi_digest_final_send(conn, ctask,
                                                     &dtask->digestbuf,
-                                                    &dtask->digest, 1)) {
+                                                    &dtask->digest, 1);
+                        if (rc) {
                                 debug_tcp("send r2t data digest 0x%x"
                                           "fail\n", dtask->digest);
-                                return -EAGAIN;
+                                return rc;
                         }
                         debug_tcp("r2t data send digest 0x%x\n",
                                   dtask->digest);
@@ -1683,11 +1700,12 @@ data_out_done:
          */
         BUG_ON(tcp_ctask->r2t_data_count - r2t->data_length < 0);
         if (conn->datadgst_en) {
-                if (iscsi_digest_final_send(conn, ctask, &dtask->digestbuf,
-                                            &dtask->digest, 1)) {
+                rc = iscsi_digest_final_send(conn, ctask, &dtask->digestbuf,
+                                            &dtask->digest, 1);
+                if (rc) {
                         debug_tcp("send last r2t data digest 0x%x"
                                   "fail\n", dtask->digest);
-                        return -EAGAIN;
+                        return rc;
                 }
                 debug_tcp("r2t done dout digest 0x%x\n", dtask->digest);
         }
@@ -1713,15 +1731,16 @@ handle_xmstate_w_pad(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;
         struct iscsi_data_task *dtask = tcp_ctask->dtask;
-        int sent;
+        int sent, rc;
 
         tcp_ctask->xmstate &= ~XMSTATE_W_PAD;
         iscsi_buf_init_iov(&tcp_ctask->sendbuf, (char*)&tcp_ctask->pad,
                             tcp_ctask->pad_count);
-        if (iscsi_sendpage(conn, &tcp_ctask->sendbuf, &tcp_ctask->pad_count,
-                           &sent)) {
+        rc = iscsi_sendpage(conn, &tcp_ctask->sendbuf, &tcp_ctask->pad_count,
+                           &sent);
+        if (rc) {
                 tcp_ctask->xmstate |= XMSTATE_W_PAD;
-                return -EAGAIN;
+                return rc;
         }
 
         if (conn->datadgst_en) {
@@ -1729,22 +1748,24 @@ handle_xmstate_w_pad(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
                                      &tcp_ctask->sendbuf.sg, 1);
                 /* imm data? */
                 if (!dtask) {
-                        if (iscsi_digest_final_send(conn, ctask,
+                        rc = iscsi_digest_final_send(conn, ctask,
                                                     &tcp_ctask->immbuf,
-                                                    &tcp_ctask->immdigest, 1)) {
+                                                    &tcp_ctask->immdigest, 1);
+                        if (rc) {
                                 debug_tcp("send padding digest 0x%x"
                                           "fail!\n", tcp_ctask->immdigest);
-                                return -EAGAIN;
+                                return rc;
                         }
                         debug_tcp("done with padding, digest 0x%x\n",
                                   tcp_ctask->datadigest);
                 } else {
-                        if (iscsi_digest_final_send(conn, ctask,
+                        rc = iscsi_digest_final_send(conn, ctask,
                                                     &dtask->digestbuf,
-                                                    &dtask->digest, 1)) {
+                                                    &dtask->digest, 1);
+                        if (rc) {
                                 debug_tcp("send padding digest 0x%x"
                                           "fail\n", dtask->digest);
-                                return -EAGAIN;
+                                return rc;
                         }
                         debug_tcp("done with padding, digest 0x%x\n",
                                   dtask->digest);
@@ -1769,10 +1790,8 @@ iscsi_tcp_ctask_xmit(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         if (ctask->mtask)
                 return rc;
 
-        if (tcp_ctask->xmstate & XMSTATE_R_HDR) {
-                rc = handle_xmstate_r_hdr(conn, tcp_ctask);
-                return rc;
-        }
+        if (tcp_ctask->xmstate & XMSTATE_R_HDR)
+                return handle_xmstate_r_hdr(conn, tcp_ctask);
 
         if (tcp_ctask->xmstate & XMSTATE_W_HDR) {
                 rc = handle_xmstate_w_hdr(conn, ctask);
@@ -1824,10 +1843,11 @@ solicit_head_again:
                 if (conn->hdrdgst_en)
                         iscsi_hdr_digest(conn, &r2t->headbuf,
                                         (u8*)r2t->dtask.hdrext);
-                if (iscsi_sendhdr(conn, &r2t->headbuf, r2t->data_count)) {
+                rc = iscsi_sendhdr(conn, &r2t->headbuf, r2t->data_count);
+                if (rc) {
                         tcp_ctask->xmstate &= ~XMSTATE_SOL_DATA;
                         tcp_ctask->xmstate |= XMSTATE_SOL_HDR;
-                        return -EAGAIN;
+                        return rc;
                 }
 
                 debug_scsi("sol dout [dsn %d itt 0x%x dlen %d sent %d]\n",
diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 256b87a85978..2673a11a9495 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -513,10 +513,11 @@ EXPORT_SYMBOL_GPL(iscsi_conn_failure);
 static int iscsi_data_xmit(struct iscsi_conn *conn)
 {
         struct iscsi_transport *tt;
+        int rc = 0;
 
         if (unlikely(conn->suspend_tx)) {
                 debug_scsi("conn %d Tx suspended!\n", conn->id);
-                return 0;
+                return -ENODATA;
         }
         tt = conn->session->tt;
 
@@ -536,13 +537,15 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
         BUG_ON(conn->ctask && conn->mtask);
 
         if (conn->ctask) {
-                if (tt->xmit_cmd_task(conn, conn->ctask))
+                rc = tt->xmit_cmd_task(conn, conn->ctask);
+                if (rc)
                         goto again;
                 /* done with this in-progress ctask */
                 conn->ctask = NULL;
         }
         if (conn->mtask) {
-                if (tt->xmit_mgmt_task(conn, conn->mtask))
+                rc = tt->xmit_mgmt_task(conn, conn->mtask);
+                if (rc)
                         goto again;
                 /* done with this in-progress mtask */
                 conn->mtask = NULL;
@@ -556,7 +559,8 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
                         list_add_tail(&conn->mtask->running,
                                       &conn->mgmt_run_list);
                         spin_unlock_bh(&conn->session->lock);
-                        if (tt->xmit_mgmt_task(conn, conn->mtask))
+                        rc = tt->xmit_mgmt_task(conn, conn->mtask);
+                        if (rc)
                                 goto again;
                 }
                 /* done with this mtask */
@@ -574,7 +578,8 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
                 if (list_empty(&conn->ctask->running))
                         list_add_tail(&conn->ctask->running, &conn->run_list);
                 spin_unlock_bh(&conn->session->lock);
-                if (tt->xmit_cmd_task(conn, conn->ctask))
+                rc = tt->xmit_cmd_task(conn, conn->ctask);
+                if (rc)
                         goto again;
         }
         /* done with this ctask */
@@ -588,32 +593,34 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
                         list_add_tail(&conn->mtask->running,
                                       &conn->mgmt_run_list);
                         spin_unlock_bh(&conn->session->lock);
-                        if (tt->xmit_mgmt_task(conn, conn->mtask))
+                        rc = tt->xmit_mgmt_task(conn, conn->mtask);
+                        if (rc)
                                 goto again;
                 }
                 /* done with this mtask */
                 conn->mtask = NULL;
         }
 
-        return 0;
+        return -ENODATA;
 
 again:
         if (unlikely(conn->suspend_tx))
-                return 0;
+                return -ENODATA;
 
-        return -EAGAIN;
+        return rc;
 }
 
 static void iscsi_xmitworker(void *data)
 {
         struct iscsi_conn *conn = data;
-
+        int rc;
         /*
          * serialize Xmit worker on a per-connection basis.
          */
         mutex_lock(&conn->xmitmutex);
-        if (iscsi_data_xmit(conn))
-                scsi_queue_work(conn->session->host, &conn->xmitwork);
+        do {
+                rc = iscsi_data_xmit(conn);
+        } while (rc >= 0 || rc == -EAGAIN);
         mutex_unlock(&conn->xmitmutex);
 }
 
diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
index 92129b97d31e..b684426a5900 100644
--- a/include/scsi/scsi_transport_iscsi.h
+++ b/include/scsi/scsi_transport_iscsi.h
@@ -57,8 +57,12 @@ struct iscsi_mgmt_task;
  *                      Called from queuecommand with session lock held.
  * @init_mgmt_task:     Initialize a iscsi_mgmt_task and any internal structs.
  *                      Called from iscsi_conn_send_generic with xmitmutex.
- * @xmit_cmd_task:      requests LLD to transfer cmd task
- * @xmit_mgmt_task:     requests LLD to transfer mgmt task
+ * @xmit_cmd_task:      Requests LLD to transfer cmd task. Returns 0 or the
+ *                      the number of bytes transferred on success, and -Exyz
+ *                      value on error.
+ * @xmit_mgmt_task:     Requests LLD to transfer mgmt task. Returns 0 or the
+ *                      the number of bytes transferred on success, and -Exyz
+ *                      value on error.
  * @cleanup_cmd_task:   requests LLD to fail cmd task. Called with xmitmutex
  *                      and session->lock after the connection has been
  *                      suspended and terminated during recovery. If called