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authorBodo Stroesser <bstroesser@ts.fujitsu.com>2020-07-26 17:35:08 +0200
committerMartin K. Petersen <martin.petersen@oracle.com>2020-07-28 22:25:29 -0400
commited212ca878972d6de88ee7f175f84399fc2e3f01 (patch)
tree1f8a54c56a2aa539e66de71cdafd0af62da4eff2 /drivers/target
parent3d3f9d56a57014174ea9b997c95b71b50fdc4cc3 (diff)
scsi: target: tcmu: Fix and simplify timeout handling
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, replace 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. Simplify the end of tcmu_handle_completions() and change 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. Link: https://lore.kernel.org/r/20200726153510.13077-7-bstroesser@ts.fujitsu.com Reviewed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/target')
-rw-r--r--drivers/target/target_core_user.c59
1 files 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 @@ out:
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",