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    Subject[PATCH 3.11 007/272] iscsi-target: Fix mutex_trylock usage in iscsit_increment_maxcmdsn
    Date
    3.11.10.1 -stable review patch.  If anyone has any objections, please let me know.

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

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

    commit 5e8e6b4b3adebf01a9d97056cbbfd8c44330df99 upstream.

    This patch fixes a >= v3.10 regression bug with mutex_trylock() usage
    within iscsit_increment_maxcmdsn(), that was originally added to allow
    for a special case where ->cmdsn_mutex was already held from the
    iscsit_execute_cmd() exception path for ib_isert.

    When !mutex_trylock() was occuring under contention during normal RX/TX
    process context codepaths, the bug was manifesting itself as the following
    protocol error:

    Received CmdSN: 0x000fcbb7 is greater than MaxCmdSN: 0x000fcbb6, protocol error.
    Received CmdSN: 0x000fcbb8 is greater than MaxCmdSN: 0x000fcbb6, protocol error.

    This patch simply avoids the direct ib_isert callback in lio_queue_status()
    for the special iscsi_execute_cmd() exception cases, that allows the problematic
    mutex_trylock() usage in iscsit_increment_maxcmdsn() to go away.

    Reported-by: Moussa Ba <moussaba@micron.com>
    Tested-by: Moussa Ba <moussaba@micron.com>
    Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    drivers/target/iscsi/iscsi_target_configfs.c | 5 +++++
    drivers/target/iscsi/iscsi_target_device.c | 6 +-----
    2 files changed, 6 insertions(+), 5 deletions(-)

    diff --git a/drivers/target/iscsi/iscsi_target_configfs.c b/drivers/target/iscsi/iscsi_target_configfs.c
    index bbfd288..752ee53 100644
    --- a/drivers/target/iscsi/iscsi_target_configfs.c
    +++ b/drivers/target/iscsi/iscsi_target_configfs.c
    @@ -1786,6 +1786,11 @@ static int lio_queue_status(struct se_cmd *se_cmd)
    struct iscsi_cmd *cmd = container_of(se_cmd, struct iscsi_cmd, se_cmd);

    cmd->i_state = ISTATE_SEND_STATUS;
    +
    + if (cmd->se_cmd.scsi_status || cmd->sense_reason) {
    + iscsit_add_cmd_to_response_queue(cmd, cmd->conn, cmd->i_state);
    + return 0;
    + }
    cmd->conn->conn_transport->iscsit_queue_status(cmd->conn, cmd);

    return 0;
    diff --git a/drivers/target/iscsi/iscsi_target_device.c b/drivers/target/iscsi/iscsi_target_device.c
    index 1b74033..4edcc47 100644
    --- a/drivers/target/iscsi/iscsi_target_device.c
    +++ b/drivers/target/iscsi/iscsi_target_device.c
    @@ -60,11 +60,7 @@ void iscsit_increment_maxcmdsn(struct iscsi_cmd *cmd, struct iscsi_session *sess

    cmd->maxcmdsn_inc = 1;

    - if (!mutex_trylock(&sess->cmdsn_mutex)) {
    - sess->max_cmd_sn += 1;
    - pr_debug("Updated MaxCmdSN to 0x%08x\n", sess->max_cmd_sn);
    - return;
    - }
    + mutex_lock(&sess->cmdsn_mutex);
    sess->max_cmd_sn += 1;
    pr_debug("Updated MaxCmdSN to 0x%08x\n", sess->max_cmd_sn);
    mutex_unlock(&sess->cmdsn_mutex);
    --
    1.8.3.2


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