linux-kernel - [PATCH v8 11/18] null_blk: Support shared tag bitmap

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Date:   Wed, 19 Aug 2020 23:20:29 +0800
From:   John Garry <john.garry@...wei.com>
To:     <axboe@...nel.dk>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <don.brace@...rosemi.com>,
        <kashyap.desai@...adcom.com>, <ming.lei@...hat.com>,
        <bvanassche@....org>, <dgilbert@...erlog.com>,
        <paolo.valente@...aro.org>, <hare@...e.de>, <hch@....de>
CC:     <sumit.saxena@...adcom.com>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <esc.storagedev@...rosemi.com>, <megaraidlinux.pdl@...adcom.com>,
        <chenxiang66@...ilicon.com>, <luojiaxing@...wei.com>,
        John Garry <john.garry@...wei.com>
Subject: [PATCH v8 11/18] null_blk: Support shared tag bitmap

Support a shared tag bitmap, whereby request tags are unique over all
submission queues, and not just per submission queue.

As such, per device total queue depth is normally hw_queue_depth *
submit_queues, but hw_queue_depth when set. And a similar story for when
shared_tags is set, where that is the queue depth over all null blk
devices.

Signed-off-by: John Garry <john.garry@...wei.com>
---
 drivers/block/null_blk_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 47a9dad880af..19c04e074880 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -164,6 +164,10 @@ static bool shared_tags;
 module_param(shared_tags, bool, 0444);
 MODULE_PARM_DESC(shared_tags, "Share tag set between devices for blk-mq");
 
+static bool g_shared_tag_bitmap;
+module_param_named(shared_tag_bitmap, g_shared_tag_bitmap, bool, 0444);
+MODULE_PARM_DESC(shared_tag_bitmap, "Use shared tag bitmap for all submission queues for blk-mq");
+
 static int g_irqmode = NULL_IRQ_SOFTIRQ;
 
 static int null_set_irqmode(const char *str, const struct kernel_param *kp)
@@ -1692,6 +1696,8 @@ static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set *set)
 	set->flags = BLK_MQ_F_SHOULD_MERGE;
 	if (g_no_sched)
 		set->flags |= BLK_MQ_F_NO_SCHED;
+	if (g_shared_tag_bitmap)
+		set->flags |= BLK_MQ_F_TAG_HCTX_SHARED;
 	set->driver_data = NULL;
 
 	if ((nullb && nullb->dev->blocking) || g_blocking)
-- 
2.26.2