Re: [PATCH RFC] iser-target: avoid reinitializing rdma contexts for isert commands

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Hi Bharat,

Thanks for the patch, comment below.

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@xxxxxxxxxxx>
---
  drivers/infiniband/ulp/isert/ib_isert.c | 7 +++++++
  drivers/infiniband/ulp/isert/ib_isert.h | 1 +
  2 files changed, 8 insertions(+)

diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 720dfb3a1ac2..fd55163801a3 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/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);

I'm not convinced this is sufficient, for reads (isert_put_datain) we
need to skip duplicating the post_recv as well.
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