During cmd timeout handling in check_timedout_devices() due to
a race it can happen, that tcmu_set_next_deadline() does not
start a timer as expected:
1) Either tcmu_check_expired_ring_cmd() checks the
inflight_queue or tcmu_check_expired_queue_cmd() checks the
qfull_queue while jiffies has the value X
2) At the end of the check the queue contains one remaining
command with deadline X (time_after(X, X) is false and
thus the command is not handled as being timed out).
3) After tcmu_check_expired_xxxxx_cmd() a timer interrupt
happens and jiffies is incremented to X+1.
4) Now tcmu_set_next_deadline() is called, but it skips
the command, since time_after(X+1, X) is true. Therefore
tcmu_set_next_deadline() finds no new deadline and stops
the timer, which it shouldn't.
Since commands that time out are removed from inflight_queue
or qfull_queue, we don't need the check with time_after() in
tcmu_set_next_deadline(), but can use the deadline from the
first cmd in the queue.
Additionally I replaced the remaining time_after() calls in
tcmu_check_expired_xxxxx_cmd() with time_after_eq(), because
it is not useful to set the timeout to deadline, but then check
for jiffies being greater than deadline.
Next I simplified the end of tcmu_handle_completions() and
changed the check for no more pending commands from
"mb->cmd_tail == mb->cmd_head"
to
"idr_is_empty(&udev->commands)"
because the old check doesn't work correctly if paddings or in
the future TMRs are in the ring.
Finally tcmu_set_next_deadline() was shifted in the source as
preparation for later implementation of tmr_notify callback.
Signed-off-by: Bodo Stroesser <bstroesser@xxxxxxxxxxxxxx>
---
drivers/target/target_core_user.c | 59 +++++++++++++++------------------------
1 file changed, 23 insertions(+), 36 deletions(-)
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index eb68c5fee7b7..bddd40f07929 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -1129,6 +1129,18 @@ tcmu_queue_cmd(struct se_cmd *se_cmd)
return scsi_ret;
}
+static void tcmu_set_next_deadline(struct list_head *queue,
+ struct timer_list *timer)
+{
+ struct tcmu_cmd *cmd;
+
+ if (!list_empty(queue)) {
+ cmd = list_first_entry(queue, struct tcmu_cmd, queue_entry);
+ mod_timer(timer, cmd->deadline);
+ } else
+ del_timer(timer);
+}
+
static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *entry)
{
struct se_cmd *se_cmd = cmd->se_cmd;
@@ -1196,25 +1208,6 @@ static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *
tcmu_free_cmd(cmd);
}
-static void tcmu_set_next_deadline(struct list_head *queue,
- struct timer_list *timer)
-{
- struct tcmu_cmd *tcmu_cmd, *tmp_cmd;
- unsigned long deadline = 0;
-
- list_for_each_entry_safe(tcmu_cmd, tmp_cmd, queue, queue_entry) {
- if (!time_after(jiffies, tcmu_cmd->deadline)) {
- deadline = tcmu_cmd->deadline;
- break;
- }
- }
-
- if (deadline)
- mod_timer(timer, deadline);
- else
- del_timer(timer);
-}
-
static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
{
struct tcmu_mailbox *mb;
@@ -1267,22 +1260,16 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
handled++;
}
- if (mb->cmd_tail == mb->cmd_head) {
- /* no more pending commands */
- del_timer(&udev->cmd_timer);
-
- if (list_empty(&udev->qfull_queue)) {
- /*
- * no more pending or waiting commands so try to
- * reclaim blocks if needed.
- */
- if (atomic_read(&global_db_count) >
- tcmu_global_max_blocks)
- schedule_delayed_work(&tcmu_unmap_work, 0);
- }
- } else if (udev->cmd_time_out) {
- tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer);
+ if (atomic_read(&global_db_count) > tcmu_global_max_blocks &&
+ idr_is_empty(&udev->commands) && list_empty(&udev->qfull_queue)) {
+ /*
+ * Allocated blocks exceeded global block limit, currently no
+ * more pending or waiting commands so try to reclaim blocks.
+ */
+ schedule_delayed_work(&tcmu_unmap_work, 0);
}
+ if (udev->cmd_time_out)
+ tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer);
return handled;
}
@@ -1291,7 +1278,7 @@ static void tcmu_check_expired_ring_cmd(struct tcmu_cmd *cmd)
{
struct se_cmd *se_cmd;
- if (!time_after(jiffies, cmd->deadline))
+ if (!time_after_eq(jiffies, cmd->deadline))
return;
set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
@@ -1310,7 +1297,7 @@ static void tcmu_check_expired_queue_cmd(struct tcmu_cmd *cmd)
{
struct se_cmd *se_cmd;
- if (!time_after(jiffies, cmd->deadline))
+ if (!time_after_eq(jiffies, cmd->deadline))
return;
pr_debug("Timing out queued cmd %p on dev %s.\n",
--
2.12.3
