iser-target: avoid reinitializing rdma contexts for isert commands

isert commands that failed during isert_rdma_rw_ctx_post() are queued to
Queue-Full(QF) queue and are scheduled to be reposted during queue-full
queue processing. During this reposting, the rdma contexts are initialised
again in isert_rdma_rw_ctx_post(), which is leaking significant memory.

unreferenced object 0xffff8830201d9640 (size 64):
  comm "kworker/0:2", pid 195, jiffies 4295374851 (age 4528.436s)
  hex dump (first 32 bytes):
    00 60 8b cb 2e 00 00 00 00 10 00 00 00 00 00 00  .`..............
    00 90 e3 cb 2e 00 00 00 00 10 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff8170711e>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff811f8ba5>] __kmalloc+0x125/0x2b0
    [<ffffffffa046b24f>] rdma_rw_ctx_init+0x15f/0x6f0 [ib_core]
    [<ffffffffa07ab644>] isert_rdma_rw_ctx_post+0xc4/0x3c0 [ib_isert]
    [<ffffffffa07ad972>] isert_put_datain+0x112/0x1c0 [ib_isert]
    [<ffffffffa07dddce>] lio_queue_data_in+0x2e/0x30 [iscsi_target_mod]
    [<ffffffffa076c322>] target_qf_do_work+0x2b2/0x4b0 [target_core_mod]
    [<ffffffff81080c3b>] process_one_work+0x1db/0x5d0
    [<ffffffff8108107d>] worker_thread+0x4d/0x3e0
    [<ffffffff81088667>] kthread+0x117/0x150
    [<ffffffff81713fa7>] ret_from_fork+0x27/0x40
    [<ffffffffffffffff>] 0xffffffffffffffff

Here is patch to use the older rdma contexts while reposting
the isert commands intead of reinitialising them.
Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/ulp/isert/ib_isert.c

@@ -2123,6 +2123,9 @@ isert_rdma_rw_ctx_post(struct isert_cmd *cmd, struct isert_conn *conn,
 	u32 rkey, offset;
 	int ret;
 
+	if (cmd->ctx_init_done)
+		goto rdma_ctx_post;
+
 	if (dir == DMA_FROM_DEVICE) {
 		addr = cmd->write_va;
 		rkey = cmd->write_stag;
@@ -2150,11 +2153,15 @@ isert_rdma_rw_ctx_post(struct isert_cmd *cmd, struct isert_conn *conn,
 				se_cmd->t_data_sg, se_cmd->t_data_nents,
 				offset, addr, rkey, dir);
 	}
+
 	if (ret < 0) {
 		isert_err("Cmd: %p failed to prepare RDMA res\n", cmd);
 		return ret;
 	}
 
+	cmd->ctx_init_done = true;
+
+rdma_ctx_post:
 	ret = rdma_rw_ctx_post(&cmd->rw, conn->qp, port_num, cqe, chain_wr);
 	if (ret < 0)
 		isert_err("Cmd: %p failed to post RDMA res\n", cmd);

drivers/infiniband/ulp/isert/ib_isert.h

@@ -126,6 +126,7 @@ struct isert_cmd {
 	struct rdma_rw_ctx	rw;
 	struct work_struct	comp_work;
 	struct scatterlist	sg;
+	bool			ctx_init_done;
 };
 
 static inline struct isert_cmd *tx_desc_to_cmd(struct iser_tx_desc *desc)