linux-toradex.git/drivers/md/dm-delay.c, branch v6.19

treewide, timers: Rename from_timer() to timer_container_of()

2025-06-08T07:07:37+00:00

Move this API to the canonical timer_*() namespace.

[ tglx: Redone against pre rc1 ]

Signed-off-by: Ingo Molnar 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/aB2X0jCKQO56WdMt@gmail.com

dm-delay: don't busy-wait in kthread

2025-05-04T09:35:05+00:00

When using a kthread to delay the IOs, dm-delay would continuously loop,
checking if IOs were ready to submit. It had a cond_resched() call in
the loop, but might still loop hundreds of millions of times waiting for
an IO that was scheduled to be submitted 10s of ms in the future. With
the change to make dm-delay over zoned devices always use kthreads
regardless of the length of the delay, this wasted work only gets worse.

To solve this and still keep roughly the same precision for very short
delays, dm-delay now calls fsleep() for 1/8th of the smallest non-zero
delay it will place on IOs, or 1 ms, whichever is smaller. The reason
that dm-delay doesn't just use the actual expiration time of the next
delayed IO to calculated the sleep time is that delay_dtr() must wait
for the kthread to finish before deleting the table. If a zoned device
with a long delay queued an IO shortly before being suspended and
removed, the IO would be flushed in delay_presuspend(), but the removing
the device would still have to wait for the remainder of the long delay.
This time is now capped at 1 ms.

Signed-off-by: Benjamin Marzinski 
Reviewed-by: Damien Le Moal 
Tested-by: Damien Le Moal 
Signed-off-by: Mikulas Patocka

dm-delay: support zoned devices

2025-03-24T17:28:32+00:00

Add support for zoned device by passing through report_zoned to the
underlying read device.

This is required to make enable xfstests xfs/311 on zoned devices.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Damien Le Moal 
Signed-off-by: Mikulas Patocka

dm-delay: remove timer_lock

2024-05-09T13:10:58+00:00

Instead of manually checking the timer details in queue_timeout(), call
timer_reduce() to start the timer or reduce the expiration time. This
avoids needing a lock.

Signed-off-by: Benjamin Marzinski 
Signed-off-by: Mike Snitzer

dm-delay: change locking to avoid contention

2024-05-09T13:10:58+00:00

The delayed_bios list is protected by one mutex shared by all dm-delay
devices. This mutex must be held whenever a bio is added or expired bios
are removed from the list.  Since a large number of expired bios could
be on the list, flush_delayed_bios() can schedule while holding the
mutex. This means a flush_delayed_bios() call on any dm-delay device can
slow down delay_map() calls on any other dm-delay device.

To keep dm-delay devices from slowing each other down and keep
processing delay bios from slowing adding delayed bios, the global mutex
has been removed, and each dm-delay device now has two locks.
delayed_bios_lock is a spinlock that must be held whenever the
delayed_bios list is accessed. process_bios_lock is a mutex that must be
held whenever a process has temporarily pulled bios off the delayed_bios
list to check which ones should be processed. It must be held until all
the bios that won't be processed are returned to the list. This is what
flush_delayed_bios() now does. The mutex is necessary to guarantee that
delay_presuspend() sees the entire list of delayed bios when it calls
flush_delayed_bios().

Signed-off-by: Benjamin Marzinski 
Signed-off-by: Mike Snitzer

dm-delay: fix max_delay calculations

2024-05-09T13:10:58+00:00

delay_ctr() pointlessly compared max_delay in cases where multiple delay
classes were initialized identically. Also, when write delays were
configured different than read delays, delay_ctr() never compared their
value against max_delay. Fix these issues.

Fixes: 70bbeb29fab0 ("dm delay: for short delays, use kthread instead of timers and wq")
Signed-off-by: Benjamin Marzinski 
Signed-off-by: Mike Snitzer

dm-delay: fix hung task introduced by kthread mode

2024-05-09T13:10:58+00:00

If the worker thread is not woken due to a bio, then it is not woken at
all. This causes the hung task check to trigger. This occurs, for
instance, when no bios are submitted. Also when a delay of 0 is
configured, delay_bio() returns without waking the worker.

Prevent the hung task check from triggering by creating the thread with
kthread_run() instead of using kthread_create() directly.

Fixes: 70bbeb29fab0 ("dm delay: for short delays, use kthread instead of timers and wq")
Signed-off-by: Joel Colledge 
Reviewed-by: Benjamin Marzinski 
Signed-off-by: Mike Snitzer

dm-delay: fix workqueue delay_timer race

2024-05-09T13:10:58+00:00

delay_timer could be pending when delay_dtr() is called. It needs to be
shut down before kdelayd_wq is destroyed, so it won't try queueing more
work to kdelayd_wq while that's getting destroyed.

Also the del_timer_sync() call in delay_presuspend() doesn't protect
against the timer getting immediately rearmed by the queued call to
flush_delayed_bios(), but there's no real harm if that does happen.
timer_delete() is less work, and is basically just as likely to stop a
pointless call to flush_delayed_bios().

Fixes: 26b9f228703f ("dm: delay target")
Signed-off-by: Benjamin Marzinski 
Signed-off-by: Mike Snitzer

dm-delay: avoid duplicate logic

2023-11-17T19:41:14+00:00

This is small refactoring of dm-delay - we avoid duplicate logic in
flush_delayed_bios and flush_delayed_bios_fast and join these two
functions into one.

We also add cond_resched() to flush_delayed_bios because the list may have
unbounded number of entries.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm-delay: fix bugs introduced by kthread mode

2023-11-17T19:41:14+00:00

This commit fixes the following bugs introduced by commit 70bbeb29fab0
("dm delay: for short delays, use kthread instead of timers and wq"):

* the function flush_worker_fn has no exit path - on unload, this
  function will just loop and consume 100% CPU without any progress

* the wake-up mechanism in flush_worker_fn is racy - a wake up will be
  missed if the process adds entries to the delayed_bios list just
  before set_current_state(TASK_INTERRUPTIBLE)

* flush_delayed_bios_fast submits a bio while holding a global mutex;
  this may deadlock if we have multiple stacked dm-delay devices and
  the underlying device attempts to acquire the mutex too

* if the target constructor fails, it will call delay_dtr. delay_dtr
  would attempt to free dc->timer_lock without it being initialized by
  the constructor.

* if the target constructor's kthread allocation fails, delay_dtr
  would crash trying to dereference dc->worker because it is non-NULL
  due to ERR_PTR.

Fixes: 70bbeb29fab0 ("dm delay: for short delays, use kthread instead of timers and wq")
Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer