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    Subject[PATCH 3.11 044/144] iscsi-target: Perform release of acknowledged tags from RX context
    Date
    3.11.10.7 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Nicholas Bellinger <nab@linux-iscsi.org>

    commit f56cbbb4b5871e5bc2838ddeeba5b29debc2a734 upstream.

    This patch converts iscsit_ack_from_expstatsn() to populate a local
    ack_list of commands, and call iscsit_free_cmd() directly from RX
    thread context, instead of using iscsit_add_cmd_to_immediate_queue()
    to queue the acknowledged commands to be released from TX thread
    context.

    It is helpful to release the acknowledge commands as quickly as
    possible, along with the associated percpu_ida tags, in order to
    prevent percpu_ida_alloc() from having to steal tags from other
    CPUs while waiting for iscsit_free_cmd() to happen from TX thread
    context.

    Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    drivers/target/iscsi/iscsi_target.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
    index 9c6136e..f6de529 100644
    --- a/drivers/target/iscsi/iscsi_target.c
    +++ b/drivers/target/iscsi/iscsi_target.c
    @@ -774,7 +774,8 @@ static void iscsit_unmap_iovec(struct iscsi_cmd *cmd)

    static void iscsit_ack_from_expstatsn(struct iscsi_conn *conn, u32 exp_statsn)
    {
    - struct iscsi_cmd *cmd;
    + LIST_HEAD(ack_list);
    + struct iscsi_cmd *cmd, *cmd_p;

    conn->exp_statsn = exp_statsn;

    @@ -782,19 +783,23 @@ static void iscsit_ack_from_expstatsn(struct iscsi_conn *conn, u32 exp_statsn)
    return;

    spin_lock_bh(&conn->cmd_lock);
    - list_for_each_entry(cmd, &conn->conn_cmd_list, i_conn_node) {
    + list_for_each_entry_safe(cmd, cmd_p, &conn->conn_cmd_list, i_conn_node) {
    spin_lock(&cmd->istate_lock);
    if ((cmd->i_state == ISTATE_SENT_STATUS) &&
    iscsi_sna_lt(cmd->stat_sn, exp_statsn)) {
    cmd->i_state = ISTATE_REMOVE;
    spin_unlock(&cmd->istate_lock);
    - iscsit_add_cmd_to_immediate_queue(cmd, conn,
    - cmd->i_state);
    + list_move_tail(&cmd->i_conn_node, &ack_list);
    continue;
    }
    spin_unlock(&cmd->istate_lock);
    }
    spin_unlock_bh(&conn->cmd_lock);
    +
    + list_for_each_entry_safe(cmd, cmd_p, &ack_list, i_conn_node) {
    + list_del(&cmd->i_conn_node);
    + iscsit_free_cmd(cmd, false);
    + }
    }

    static int iscsit_allocate_iovecs(struct iscsi_cmd *cmd)
    --
    1.9.1


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