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From: Jeffle Xu <[email protected]>
To: [email protected], [email protected]
Cc: [email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected]
Subject: [PATCH v5 04/12] block: add poll_capable method to support bio-based IO polling
Date: Wed,  3 Mar 2021 19:57:32 +0800	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

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out-of-date.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 <[email protected]>
---
 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


  parent reply	other threads:[~2021-03-04  0:26 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-03 11:57 [PATCH v5 00/12] dm: support polling Jeffle Xu
2021-03-03 11:57 ` [PATCH v5 01/12] block: move definition of blk_qc_t to types.h Jeffle Xu
2021-03-03 11:57 ` [PATCH v5 02/12] block: add queue_to_disk() to get gendisk from request_queue Jeffle Xu
2021-03-03 11:57 ` [PATCH v5 03/12] block: add poll method to support bio-based IO polling Jeffle Xu
2021-03-10 22:01   ` Mike Snitzer
2021-03-11  5:31     ` [dm-devel] " JeffleXu
2021-03-03 11:57 ` Jeffle Xu [this message]
2021-03-10 22:21   ` [PATCH v5 04/12] block: add poll_capable " Mike Snitzer
2021-03-11  5:43     ` [dm-devel] " JeffleXu
2021-03-03 11:57 ` [PATCH v5 05/12] blk-mq: extract one helper function polling hw queue Jeffle Xu
2021-03-03 11:57 ` [PATCH v5 06/12] blk-mq: add iterator for polling hw queues Jeffle Xu
2021-03-03 11:57 ` [PATCH v5 07/12] blk-mq: add one helper function getting hw queue Jeffle Xu
2021-03-03 11:57 ` [PATCH v5 08/12] dm: always return BLK_QC_T_NONE for bio-based device Jeffle Xu
2021-03-03 11:57 ` [PATCH v5 09/12] nvme/pci: don't wait for locked polling queue Jeffle Xu
2021-03-10 21:57   ` Mike Snitzer
2021-03-03 11:57 ` [PATCH v5 10/12] block: fastpath for bio-based polling Jeffle Xu
2021-03-10 23:18   ` Mike Snitzer
2021-03-11  6:36     ` [dm-devel] " JeffleXu
2021-03-12  2:26       ` JeffleXu
2021-03-11 13:56   ` Ming Lei
2021-03-12  1:56     ` [dm-devel] " JeffleXu
2021-03-03 11:57 ` [PATCH v5 11/12] block: sub-fastpath " Jeffle Xu
2021-03-03 11:57 ` [PATCH v5 12/12] dm: support IO polling for bio-based dm device Jeffle Xu

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