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Subject[PATCH-v2 3/4] target: Fix bug with task_sg chained transport_free_dev_tasks release
Date
From: Nicholas Bellinger <nab@linux-iscsi.org>

This patch addresses a bug in the target core release path for HW
operation where transport_free_dev_tasks() was incorrectly being called
from transport_lun_remove_cmd() while releasing a se_cmd reference and
calling struct target_core_fabric_ops->queue_data_in().

This would result in a OOPs with HW target mode when the release of
se_task->task_sg[] would happen before pci_unmap_sg() can be called in
HW target mode fabric module code. This patch addresses the issue by
moving transport_free_dev_tasks() from transport_lun_remove_cmd() into
transport_generic_free_cmd(), and adding TRANSPORT_FREE_CMD_INTR and
transport_generic_free_cmd_intr() to allow se_cmd descriptor release
to happen fromfrom within transport_processing_thread() process context
when release of se_cmd is not possible from HW interrupt context.

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
drivers/target/target_core_transport.c | 13 ++++++++++++-
include/target/target_core_base.h | 1 +
include/target/target_core_transport.h | 1 +
3 files changed, 14 insertions(+), 1 deletions(-)
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index fefe10a..3eeb3e2 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -762,7 +762,6 @@ static void transport_lun_remove_cmd(struct se_cmd *cmd)
transport_all_task_dev_remove_state(cmd);
spin_unlock_irqrestore(&T_TASK(cmd)->t_state_lock, flags);

- transport_free_dev_tasks(cmd);

check_lun:
spin_lock_irqsave(&lun->lun_cmd_lock, flags);
@@ -2058,6 +2057,13 @@ int transport_generic_handle_tmr(
}
EXPORT_SYMBOL(transport_generic_handle_tmr);

+void transport_generic_free_cmd_intr(
+ struct se_cmd *cmd)
+{
+ transport_add_cmd_to_queue(cmd, TRANSPORT_FREE_CMD_INTR);
+}
+EXPORT_SYMBOL(transport_generic_free_cmd_intr);
+
static int transport_stop_tasks_for_cmd(struct se_cmd *cmd)
{
struct se_task *task, *task_tmp;
@@ -5301,6 +5307,8 @@ void transport_generic_free_cmd(
if (wait_for_tasks && cmd->transport_wait_for_tasks)
cmd->transport_wait_for_tasks(cmd, 0, 0);

+ transport_free_dev_tasks(cmd);
+
transport_generic_remove(cmd, release_to_pool,
session_reinstatement);
}
@@ -6136,6 +6144,9 @@ get_cmd:
case TRANSPORT_REMOVE:
transport_generic_remove(cmd, 1, 0);
break;
+ case TRANSPORT_FREE_CMD_INTR:
+ transport_generic_free_cmd(cmd, 0, 1, 0);
+ break;
case TRANSPORT_PROCESS_TMR:
transport_generic_do_tmr(cmd);
break;
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 1d3b5b2..561ac99 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -98,6 +98,7 @@ enum transport_state_table {
TRANSPORT_REMOVE = 14,
TRANSPORT_FREE = 15,
TRANSPORT_NEW_CMD_MAP = 16,
+ TRANSPORT_FREE_CMD_INTR = 17,
};

/* Used for struct se_cmd->se_cmd_flags */
diff --git a/include/target/target_core_transport.h b/include/target/target_core_transport.h
index 59aa464..24a1c6c 100644
--- a/include/target/target_core_transport.h
+++ b/include/target/target_core_transport.h
@@ -172,6 +172,7 @@ extern int transport_generic_handle_cdb_map(struct se_cmd *);
extern int transport_generic_handle_data(struct se_cmd *);
extern void transport_new_cmd_failure(struct se_cmd *);
extern int transport_generic_handle_tmr(struct se_cmd *);
+extern void transport_generic_free_cmd_intr(struct se_cmd *);
extern void __transport_stop_task_timer(struct se_task *, unsigned long *);
extern unsigned char transport_asciihex_to_binaryhex(unsigned char val[2]);
extern int transport_generic_map_mem_to_cmd(struct se_cmd *cmd, struct scatterlist *, u32,
--
1.7.5.1


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