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Commit 5e8e6b4b authored by Nicholas Bellinger's avatar Nicholas Bellinger
Browse files

iscsi-target: Fix mutex_trylock usage in iscsit_increment_maxcmdsn 



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: default avatarMoussa Ba <moussaba@micron.com>
Tested-by: default avatarMoussa Ba <moussaba@micron.com>
Cc: <stable@vger.kernel.org> # v3.10+
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent 0f59cc3f

drivers/target/iscsi/iscsi_target_configfs.c

+5 −0
Original line number Diff line number Diff line
@@ -1790,6 +1790,11 @@ 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;

drivers/target/iscsi/iscsi_target_device.c

+1 −5
Original line number Diff line number Diff line
@@ -58,11 +58,7 @@ 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);