[SCSI] libiscsi: Restructure iscsi_tcp r2t response logic

Restructure the iscsi_tcp_r2t_rsp routine in order to avoid allocating
r2t from r2tpool.queue and returning it back in case the parameters
rhdr->data_length and or rhdr->data_offset prohibit the requing.

Since the values of these parameters are known prior to the allocation,
we can pre-check and thus avoid futile allocations.

[jejb: checkpatch fixes]
Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 22 insertions, 21 deletions

diff --git a/drivers/scsi/libiscsi_tcp.c b/drivers/scsi/libiscsi_tcp.c
index 1d58d5336018..2f738dddd078 100644
--- a/drivers/scsi/libiscsi_tcp.c
+++ b/drivers/scsi/libiscsi_tcp.c
@@ -529,6 +529,8 @@ static int iscsi_tcp_r2t_rsp(struct iscsi_conn *conn, struct iscsi_task *task)
         struct iscsi_r2t_rsp *rhdr = (struct iscsi_r2t_rsp *)tcp_conn->in.hdr;
         struct iscsi_r2t_info *r2t;
         int r2tsn = be32_to_cpu(rhdr->r2tsn);
+        u32 data_length;
+        u32 data_offset;
         int rc;
 
         if (tcp_conn->in.datalen) {
@@ -554,40 +556,39 @@ static int iscsi_tcp_r2t_rsp(struct iscsi_conn *conn, struct iscsi_task *task)
                 return 0;
         }
 
-        rc = kfifo_out(&tcp_task->r2tpool.queue, (void*)&r2t, sizeof(void*));
-        if (!rc) {
-                iscsi_conn_printk(KERN_ERR, conn, "Could not allocate R2T. "
-                                  "Target has sent more R2Ts than it "
-                                  "negotiated for or driver has leaked.\n");
-                return ISCSI_ERR_PROTO;
-        }
-
-        r2t->exp_statsn = rhdr->statsn;
-        r2t->data_length = be32_to_cpu(rhdr->data_length);
-        if (r2t->data_length == 0) {
+        data_length = be32_to_cpu(rhdr->data_length);
+        if (data_length == 0) {
                 iscsi_conn_printk(KERN_ERR, conn,
                                   "invalid R2T with zero data len\n");
-                kfifo_in(&tcp_task->r2tpool.queue, (void*)&r2t,
-                            sizeof(void*));
                 return ISCSI_ERR_DATALEN;
         }
 
-        if (r2t->data_length > session->max_burst)
+        if (data_length > session->max_burst)
                 ISCSI_DBG_TCP(conn, "invalid R2T with data len %u and max "
                               "burst %u. Attempting to execute request.\n",
-                              r2t->data_length, session->max_burst);
+                              data_length, session->max_burst);
 
-        r2t->data_offset = be32_to_cpu(rhdr->data_offset);
-        if (r2t->data_offset + r2t->data_length > scsi_out(task->sc)->length) {
+        data_offset = be32_to_cpu(rhdr->data_offset);
+        if (data_offset + data_length > scsi_out(task->sc)->length) {
                 iscsi_conn_printk(KERN_ERR, conn,
                                   "invalid R2T with data len %u at offset %u "
-                                  "and total length %d\n", r2t->data_length,
-                                  r2t->data_offset, scsi_out(task->sc)->length);
-                kfifo_in(&tcp_task->r2tpool.queue, (void*)&r2t,
-                            sizeof(void*));
+                                  "and total length %d\n", data_length,
+                                  data_offset, scsi_out(task->sc)->length);
                 return ISCSI_ERR_DATALEN;
         }
 
+        rc = kfifo_out(&tcp_task->r2tpool.queue, (void *)&r2t, sizeof(void *));
+        if (!rc) {
+                iscsi_conn_printk(KERN_ERR, conn, "Could not allocate R2T. "
+                                  "Target has sent more R2Ts than it "
+                                  "negotiated for or driver has leaked.\n");
+                return ISCSI_ERR_PROTO;
+        }
+
+        r2t->exp_statsn = rhdr->statsn;
+        r2t->data_length = data_length;
+        r2t->data_offset = data_offset;
+
         r2t->ttt = rhdr->ttt; /* no flip */
         r2t->datasn = 0;
         r2t->sent = 0;