| From | Greg Kroah-Hartman <> | Subject | [ 016/100] iscsi-target: Fix immediate queue starvation regression with DATAIN | Date | Tue, 12 Mar 2013 15:31:01 -0700 |
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3.8-stable review patch. If anyone has any objections, please let me know.
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From: Nicholas Bellinger <nab@linux-iscsi.org>
commit fd3a9025c0349bc9b01d627529f54e6e1e389015 upstream.
This patch addresses a v3.5+ regression in iscsi-target where TX thread process context -> handle_response_queue() execution is allowed to run unbounded while servicing constant outgoing flow of ISTATE_SEND_DATAIN response state.
This ends up preventing memory release of StatSN acknowledged commands in a timely manner when under heavy large block streaming DATAIN workloads.
The regression bug was initially introduced with:
commit 6f3c0e69a9c20441bdc6d3b2d18b83b244384ec6 Author: Andy Grover <agrover@redhat.com> Date: Tue Apr 3 15:51:09 2012 -0700
target/iscsi: Refactor target_tx_thread immediate+response queue loops
Go ahead and follow original iscsi_target_tx_thread() logic and check to break for immediate queue processing after each DataIN Sequence and/or Response PDU has been sent.
Reported-by: Benjamin ESTRABAUD <be@mpstor.com> Cc: Andy Grover <agrover@redhat.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/target/iscsi/iscsi_target.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
--- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -3570,6 +3570,10 @@ check_rsp_state: spin_lock_bh(&cmd->istate_lock); cmd->i_state = ISTATE_SENT_STATUS; spin_unlock_bh(&cmd->istate_lock); + + if (atomic_read(&conn->check_immediate_queue)) + return 1; + continue; } else if (ret == 2) { /* Still must send status, @@ -3659,7 +3663,7 @@ check_rsp_state: } if (atomic_read(&conn->check_immediate_queue)) - break; + return 1; } return 0; @@ -3703,12 +3707,15 @@ restart: signal_pending(current)) goto transport_err; +get_immediate: ret = handle_immediate_queue(conn); if (ret < 0) goto transport_err; ret = handle_response_queue(conn); - if (ret == -EAGAIN) + if (ret == 1) + goto get_immediate; + else if (ret == -EAGAIN) goto restart; else if (ret < 0) goto transport_err;
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