Re: [PATCH 09/18] ledtrig-blkdev: Periodically check devices for activity & blink LEDs

Greg KH
2021-09-04T06:01:46Z

On Fri, Sep 03, 2021 at 03:45:39PM -0500, Ian Pilcher wrote:
> Use a delayed workqueue to periodically check configured block devices for
> activity since the last check. Blink LEDs associated with devices on which
> the configured type of activity (read/write) has occurred.
>
> Signed-off-by: Ian Pilcher <arequipeno@gmail.com>
> ---
> drivers/leds/trigger/ledtrig-blkdev.c | 88 +++++++++++++++++++++++++++
> 1 file changed, 88 insertions(+)
>
> diff --git a/drivers/leds/trigger/ledtrig-blkdev.c b/drivers/leds/trigger/ledtrig-blkdev.c
> index 1f319529c3be..37ba9bb3542e 100644
> --- a/drivers/leds/trigger/ledtrig-blkdev.c
> +++ b/drivers/leds/trigger/ledtrig-blkdev.c
> @@ -7,7 +7,9 @@
> */
>
> #include <linux/ctype.h>
> +#include <linux/leds.h>
> #include <linux/module.h>
> +#include <linux/part_stat.h>
>
> #include "ledtrig-blkdev.h"
>
> @@ -68,6 +70,10 @@ static unsigned int ledtrig_blkdev_count;
> /* How often to check for drive activity - in jiffies */
> static unsigned int ledtrig_blkdev_interval;
>
> +/* Delayed work used to periodically check for activity & blink LEDs */
> +static void blkdev_process(struct work_struct *const work);
> +static DECLARE_DELAYED_WORK(ledtrig_blkdev_work, blkdev_process);
> +
>
> /*
> *
> @@ -110,3 +116,85 @@ static bool blkdev_write_mode(const enum ledtrig_blkdev_mode mode)
> {
> return mode != LEDTRIG_BLKDEV_MODE_RO;
> }
> +
> +
> +/*
> + *
> + * Periodically check for device acitivity and blink LEDs
> + *
> + */
> +
> +static void blkdev_blink(const struct ledtrig_blkdev_led *const led)
> +{
> + unsigned long delay_on = READ_ONCE(led->blink_msec);
> + unsigned long delay_off = 1; /* 0 leaves LED turned on */
> +
> + led_blink_set_oneshot(led->led_dev, &delay_on, &delay_off, 0);
> +}
> +
> +static void blkdev_update_disk(struct ledtrig_blkdev_disk *const disk,
> + const unsigned int generation)
> +{
> + const struct block_device *const part0 = disk->gd->part0;
> + const unsigned long read_ios = part_stat_read(part0, ios[STAT_READ]);
> + const unsigned long write_ios = part_stat_read(part0, ios[STAT_WRITE])
> + + part_stat_read(part0, ios[STAT_DISCARD])
> + + part_stat_read(part0, ios[STAT_FLUSH]);
> +
> + if (disk->read_ios != read_ios) {
> + disk->read_act = true;
> + disk->read_ios = read_ios;
> + } else {
> + disk->read_act = false;
> + }
> +
> + if (disk->write_ios != write_ios) {
> + disk->write_act = true;
> + disk->write_ios = write_ios;
> + } else {
> + disk->write_act = false;
> + }
> +
> + disk->generation = generation;
> +}
> +
> +static void blkdev_process(struct work_struct *const work)
> +{
> + static unsigned int generation;
> +
> + struct ledtrig_blkdev_led *led;
> + struct ledtrig_blkdev_link *link;
> + unsigned long delay;
> +
> + if (!mutex_trylock(&ledtrig_blkdev_mutex))
> + goto exit_reschedule;
> +
> + hlist_for_each_entry(led, &ledtrig_blkdev_leds, leds_node) {
> +
> + hlist_for_each_entry(link, &led->disks, led_disks_node) {
> +
> + struct ledtrig_blkdev_disk *const disk = link->disk;
> +
> + if (disk->generation != generation)
> + blkdev_update_disk(disk, generation);
> +
> + if (disk->read_act && blkdev_read_mode(led->mode)) {
> + blkdev_blink(led);
> + break;
> + }
> +
> + if (disk->write_act && blkdev_write_mode(led->mode)) {
> + blkdev_blink(led);
> + break;
> + }
> + }
> + }
> +
> + ++generation;
> +
> + mutex_unlock(&ledtrig_blkdev_mutex);
> +
> +exit_reschedule:
> + delay = READ_ONCE(ledtrig_blkdev_interval);
> + WARN_ON_ONCE(!schedule_delayed_work(&ledtrig_blkdev_work, delay));

You just rebooted a machine if it hit this :(

Please never use WARN_ON() in new code unless the machine is really
broken and you can not do anything else here.

thanks,

greg k-h