From c125311d96b1bfcce0f5930a4f0fdfe39ea14f7c Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 23 Aug 2018 09:34:46 -0600
Subject: [PATCH] blk-wbt: don't maintain inflight counts if disabled
A previous commit removed the ability to have per-rq flags. We used
those flags to maintain inflight counts. Since we don't have those
anymore, we have to always maintain inflight counts, even if wbt is
disabled. This is clearly suboptimal.
Add a queue quiesce around changing the wbt latency settings from sysfs
to work around this. With that, we can reliably put the enabled check in
our bio_to_wbt_flags(), since we know the WBT_TRACKED flag will be
consistent for the lifetime of the request.
Fixes: c1c80384c8f ("block: remove external dependency on wbt_flags")
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-sysfs.c | 19 ++++++++++++++++++-
block/blk-wbt.c | 3 +++
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index bb109bb0a0553..3772671cf2bc5 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -453,9 +453,26 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
else if (val >= 0)
val *= 1000ULL;
- wbt_set_min_lat(q, val);
+ /*
+ * Ensure that the queue is idled, in case the latency update
+ * ends up either enabling or disabling wbt completely. We can't
+ * have IO inflight if that happens.
+ */
+ if (q->mq_ops) {
+ blk_mq_freeze_queue(q);
+ blk_mq_quiesce_queue(q);
+ } else
+ blk_queue_bypass_start(q);
+ wbt_set_min_lat(q, val);
wbt_update_limits(q);
+
+ if (q->mq_ops) {
+ blk_mq_unquiesce_queue(q);
+ blk_mq_unfreeze_queue(q);
+ } else
+ blk_queue_bypass_end(q);
+
return count;
}
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index c9358f1981fb7..84507d3e9a981 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -540,6 +540,9 @@ static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio)
{
enum wbt_flags flags = 0;
+ if (!rwb_enabled(rwb))
+ return 0;
+
if (bio_op(bio) == REQ_OP_READ) {
flags = WBT_READ;
} else if (wbt_should_throttle(rwb, bio)) {
--
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