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out-of-date.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@xxxxxxxxxxxxxxxxx>
---
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 0f4f0c8a7825..367c1d9a55c6 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 9dc83c30e7bc..7df40792c032 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1867,6 +1867,7 @@ static inline void blk_ksm_unregister(struct request_queue *q) { }
struct block_device_operations {
blk_qc_t (*submit_bio) (struct bio *bio);
int (*poll)(struct request_queue *q, blk_qc_t cookie);
+ bool (*poll_capable)(struct gendisk *disk);
int (*open) (struct block_device *, fmode_t);
void (*release) (struct gendisk *, fmode_t);
int (*rw_page)(struct block_device *, sector_t, struct page *, unsigned int);
--
2.27.0
