[dm-devel] [PATCH V4 11/12] block: add poll_capable method to support bio-based IO polling
Hannes Reinecke
hare at suse.de
Tue Mar 30 06:26:47 UTC 2021
On 3/29/21 5:26 PM, Ming Lei wrote:
> From: Jeffle Xu <jefflexu at linux.alibaba.com>
>
> This method can be used to check if bio-based device supports IO polling
> or not. For mq devices, checking for hw queue in polling mode is
> adequate, while the sanity check shall be implementation specific for
> bio-based devices. For example, dm device needs to check if all
> underlying devices are capable of IO polling.
>
> Though bio-based device may have done the sanity check during the
> device initialization phase, cacheing the result of this sanity check
> (such as by cacheing in the queue_flags) may not work. Because for dm
> devices, users could change the state of the underlying devices through
> '/sys/block/<dev>/io_poll', bypassing the dm device above. In this case,
> the cached result of the very beginning sanity check could be
> out-of-date. Thus the sanity check needs to be done every time 'io_poll'
> is to be modified.
>
> Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
> ---
> block/blk-sysfs.c | 14 +++++++++++---
> include/linux/blkdev.h | 1 +
> 2 files changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index db3268d41274..c8e7e4af66cb 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -426,9 +426,17 @@ static ssize_t queue_poll_store(struct request_queue *q, const char *page,
> unsigned long poll_on;
> ssize_t ret;
>
> - if (!q->tag_set || q->tag_set->nr_maps <= HCTX_TYPE_POLL ||
> - !q->tag_set->map[HCTX_TYPE_POLL].nr_queues)
> - return -EINVAL;
> + if (queue_is_mq(q)) {
> + if (!q->tag_set || q->tag_set->nr_maps <= HCTX_TYPE_POLL ||
> + !q->tag_set->map[HCTX_TYPE_POLL].nr_queues)
> + return -EINVAL;
> + } else {
> + struct gendisk *disk = queue_to_disk(q);
> +
> + if (!disk->fops->poll_capable ||
> + !disk->fops->poll_capable(disk))
> + return -EINVAL;
> + }
>
> ret = queue_var_store(&poll_on, page, count);
> if (ret < 0)
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index bfab74b45f15..a46f975f2a2f 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1881,6 +1881,7 @@ struct block_device_operations {
> int (*report_zones)(struct gendisk *, sector_t sector,
> unsigned int nr_zones, report_zones_cb cb, void *data);
> char *(*devnode)(struct gendisk *disk, umode_t *mode);
> + bool (*poll_capable)(struct gendisk *disk);
> struct module *owner;
> const struct pr_ops *pr_ops;
> };
>
I really wonder how this would work for nvme multipath; but I guess it
doesn't change the current situation.
So:
Reviewed-by: Hannes Reinecke <hare at suse.de>
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare at suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
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