* [PATCH v2 1/3] wbt: don't show valid wbt_lat_usec in sysfs while wbt is disabled
2022-09-19 7:09 [PATCH v2 0/3] blk-wbt: simple improvment to enable wbt correctly Yu Kuai
@ 2022-09-19 7:09 ` Yu Kuai
2022-09-19 7:09 ` [PATCH v2 2/3] block: add a helper to check elevator name Yu Kuai
2022-09-19 7:09 ` [PATCH v2 3/3] blk-wbt: don't enable throttling if default elevator is bfq Yu Kuai
2 siblings, 0 replies; 6+ messages in thread
From: Yu Kuai @ 2022-09-19 7:09 UTC (permalink / raw)
To: paolo.valente, axboe
Cc: linux-block, linux-kernel, yukuai3, yukuai1, yi.zhang
From: Yu Kuai <yukuai3@huawei.com>
Currently, if wbt is initialized and then disabled by
wbt_disable_default(), sysfs will still show valid wbt_lat_usec, which
will confuse users that wbt is still enabled.
This patch shows wbt_lat_usec as zero and forbid to set it while wbt
is disabled.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reported-and-tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
---
block/blk-sysfs.c | 9 ++++++++-
block/blk-wbt.c | 7 +++++++
block/blk-wbt.h | 5 +++++
3 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index e1f009aba6fd..1955bb6a284d 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -467,10 +467,14 @@ static ssize_t queue_io_timeout_store(struct request_queue *q, const char *page,
static ssize_t queue_wb_lat_show(struct request_queue *q, char *page)
{
+ u64 lat;
+
if (!wbt_rq_qos(q))
return -EINVAL;
- return sprintf(page, "%llu\n", div_u64(wbt_get_min_lat(q), 1000));
+ lat = wbt_disabled(q) ? 0 : div_u64(wbt_get_min_lat(q), 1000);
+
+ return sprintf(page, "%llu\n", lat);
}
static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
@@ -493,6 +497,9 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
return ret;
}
+ if (wbt_disabled(q))
+ return -EINVAL;
+
if (val == -1)
val = wbt_default_latency_nsec(q);
else if (val >= 0)
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index a9982000b667..68851c2c02d2 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -422,6 +422,13 @@ static void wbt_update_limits(struct rq_wb *rwb)
rwb_wake_all(rwb);
}
+bool wbt_disabled(struct request_queue *q)
+{
+ struct rq_qos *rqos = wbt_rq_qos(q);
+
+ return !rqos || RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT;
+}
+
u64 wbt_get_min_lat(struct request_queue *q)
{
struct rq_qos *rqos = wbt_rq_qos(q);
diff --git a/block/blk-wbt.h b/block/blk-wbt.h
index 7e44eccc676d..e42465ddcbb6 100644
--- a/block/blk-wbt.h
+++ b/block/blk-wbt.h
@@ -94,6 +94,7 @@ void wbt_enable_default(struct request_queue *);
u64 wbt_get_min_lat(struct request_queue *q);
void wbt_set_min_lat(struct request_queue *q, u64 val);
+bool wbt_disabled(struct request_queue *);
void wbt_set_write_cache(struct request_queue *, bool);
@@ -125,6 +126,10 @@ static inline u64 wbt_default_latency_nsec(struct request_queue *q)
{
return 0;
}
+static inline bool wbt_disabled(struct request_queue *q)
+{
+ return true;
+}
#endif /* CONFIG_BLK_WBT */
--
2.31.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v2 2/3] block: add a helper to check elevator name
2022-09-19 7:09 [PATCH v2 0/3] blk-wbt: simple improvment to enable wbt correctly Yu Kuai
2022-09-19 7:09 ` [PATCH v2 1/3] wbt: don't show valid wbt_lat_usec in sysfs while wbt is disabled Yu Kuai
@ 2022-09-19 7:09 ` Yu Kuai
2022-09-19 7:09 ` [PATCH v2 3/3] blk-wbt: don't enable throttling if default elevator is bfq Yu Kuai
2 siblings, 0 replies; 6+ messages in thread
From: Yu Kuai @ 2022-09-19 7:09 UTC (permalink / raw)
To: paolo.valente, axboe
Cc: linux-block, linux-kernel, yukuai3, yukuai1, yi.zhang
From: Yu Kuai <yukuai3@huawei.com>
The helper will be used in later patch to make sure wbt is not enabled
if default io scheduler is bfq.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
block/elevator.h | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/block/elevator.h b/block/elevator.h
index 3f0593b3bf9d..2ddc738cae97 100644
--- a/block/elevator.h
+++ b/block/elevator.h
@@ -104,6 +104,11 @@ struct elevator_queue
DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
};
+static inline bool check_elevator_name(struct elevator_queue *elevator,
+ const char *name)
+{
+ return elevator && !strcmp(elevator->type->elevator_name, name);
+}
/*
* block elevator interface
*/
--
2.31.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v2 3/3] blk-wbt: don't enable throttling if default elevator is bfq
2022-09-19 7:09 [PATCH v2 0/3] blk-wbt: simple improvment to enable wbt correctly Yu Kuai
2022-09-19 7:09 ` [PATCH v2 1/3] wbt: don't show valid wbt_lat_usec in sysfs while wbt is disabled Yu Kuai
2022-09-19 7:09 ` [PATCH v2 2/3] block: add a helper to check elevator name Yu Kuai
@ 2022-09-19 7:09 ` Yu Kuai
2022-09-20 7:25 ` Christoph Hellwig
2 siblings, 1 reply; 6+ messages in thread
From: Yu Kuai @ 2022-09-19 7:09 UTC (permalink / raw)
To: paolo.valente, axboe
Cc: linux-block, linux-kernel, yukuai3, yukuai1, yi.zhang
From: Yu Kuai <yukuai3@huawei.com>
Commit b5dc5d4d1f4f ("block,bfq: Disable writeback throttling") tries to
disable wbt for bfq, it's done by calling wbt_disable_default() in
bfq_init_queue(). However, wbt is still enabled if default elevator is
bfq:
device_add_disk
elevator_init_mq
bfq_init_queue
wbt_disable_default -> done nothing
blk_register_queue
wbt_enable_default -> wbt is enabled
Fix the problem by checking elevator name if wbt_enable_default() is
called from blk_register_queue().
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
block/bfq-iosched.c | 2 +-
block/blk-sysfs.c | 2 +-
block/blk-wbt.c | 6 +++++-
block/blk-wbt.h | 5 +++--
4 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 7ea427817f7f..f769c90744fd 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -7045,7 +7045,7 @@ static void bfq_exit_queue(struct elevator_queue *e)
#endif
blk_stat_disable_accounting(bfqd->queue);
- wbt_enable_default(bfqd->queue);
+ wbt_enable_default(bfqd->queue, false);
kfree(bfqd);
}
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 1955bb6a284d..3e8adb95ff02 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -850,7 +850,7 @@ int blk_register_queue(struct gendisk *disk)
goto put_dev;
blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);
- wbt_enable_default(q);
+ wbt_enable_default(q, true);
blk_throtl_register_queue(q);
/* Now everything is ready and send out KOBJ_ADD uevent */
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 68851c2c02d2..c6256e7c9e8e 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -27,6 +27,7 @@
#include "blk-wbt.h"
#include "blk-rq-qos.h"
+#include "elevator.h"
#define CREATE_TRACE_POINTS
#include <trace/events/wbt.h>
@@ -643,10 +644,13 @@ void wbt_set_write_cache(struct request_queue *q, bool write_cache_on)
/*
* Enable wbt if defaults are configured that way
*/
-void wbt_enable_default(struct request_queue *q)
+void wbt_enable_default(struct request_queue *q, bool check_elevator)
{
struct rq_qos *rqos = wbt_rq_qos(q);
+ if (check_elevator && check_elevator_name(q->elevator, "bfq"))
+ return;
+
/* Throttling already enabled? */
if (rqos) {
if (RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
diff --git a/block/blk-wbt.h b/block/blk-wbt.h
index e42465ddcbb6..eb028febaff0 100644
--- a/block/blk-wbt.h
+++ b/block/blk-wbt.h
@@ -90,7 +90,7 @@ static inline unsigned int wbt_inflight(struct rq_wb *rwb)
int wbt_init(struct request_queue *);
void wbt_disable_default(struct request_queue *);
-void wbt_enable_default(struct request_queue *);
+void wbt_enable_default(struct request_queue *, bool);
u64 wbt_get_min_lat(struct request_queue *q);
void wbt_set_min_lat(struct request_queue *q, u64 val);
@@ -109,7 +109,8 @@ static inline int wbt_init(struct request_queue *q)
static inline void wbt_disable_default(struct request_queue *q)
{
}
-static inline void wbt_enable_default(struct request_queue *q)
+static inline void wbt_enable_default(struct request_queue *q,
+ bool check_elevator)
{
}
static inline void wbt_set_write_cache(struct request_queue *q, bool wc)
--
2.31.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH v2 3/3] blk-wbt: don't enable throttling if default elevator is bfq
2022-09-19 7:09 ` [PATCH v2 3/3] blk-wbt: don't enable throttling if default elevator is bfq Yu Kuai
@ 2022-09-20 7:25 ` Christoph Hellwig
2022-09-20 7:48 ` Yu Kuai
0 siblings, 1 reply; 6+ messages in thread
From: Christoph Hellwig @ 2022-09-20 7:25 UTC (permalink / raw)
To: Yu Kuai; +Cc: paolo.valente, axboe, linux-block, linux-kernel, yukuai3,
yi.zhang
Matching names is always is a bad idea.
Just ad a flags field to elevator_mq_ops, add a DISABLE_WBT flag
to it, and check for that and everything should become much, much
simpler.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 3/3] blk-wbt: don't enable throttling if default elevator is bfq
2022-09-20 7:25 ` Christoph Hellwig
@ 2022-09-20 7:48 ` Yu Kuai
0 siblings, 0 replies; 6+ messages in thread
From: Yu Kuai @ 2022-09-20 7:48 UTC (permalink / raw)
To: Christoph Hellwig, Yu Kuai
Cc: paolo.valente, axboe, linux-block, linux-kernel, yi.zhang,
yukuai (C)
Hi, Christoph!
在 2022/09/20 15:25, Christoph Hellwig 写道:
> Matching names is always is a bad idea.
>
> Just ad a flags field to elevator_mq_ops, add a DISABLE_WBT flag
> to it, and check for that and everything should become much, much
> simpler.
Thanks for the adivce, that is a good idea!
Kuai
>
> .
>
^ permalink raw reply [flat|nested] 6+ messages in thread