* [PATCH 0/2] blk-wbt: fix two wbt enable problems
@ 2021-06-19 9:36 Zhang Yi
2021-06-19 9:36 ` [PATCH 1/2] blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled() Zhang Yi
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Zhang Yi @ 2021-06-19 9:36 UTC (permalink / raw)
To: linux-block; +Cc: axboe, jbacik, yi.zhang, yukuai3
Commit a79050434b45 ("blk-rq-qos: refactor out common elements of
blk-wbt") introduce two wbt enable problems. The first one will cause
false positive check by rwb_enabled() and lead to IO hung, the second
one is wbt_enable_default() could not re-enable wbt after switch
elevator back from bfq to other one.
Zhang Yi (2):
blk-wbt: introduce a new disable state to prevent false positive by
rwb_enabled()
blk-wbt: make sure throttle is enabled properly
block/blk-wbt.c | 11 ++++++++---
block/blk-wbt.h | 1 +
2 files changed, 9 insertions(+), 3 deletions(-)
--
2.31.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH 1/2] blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled()
2021-06-19 9:36 [PATCH 0/2] blk-wbt: fix two wbt enable problems Zhang Yi
@ 2021-06-19 9:36 ` Zhang Yi
2021-06-19 9:37 ` [PATCH 2/2] blk-wbt: make sure throttle is enabled properly Zhang Yi
2021-06-21 16:07 ` [PATCH 0/2] blk-wbt: fix two wbt enable problems Jens Axboe
2 siblings, 0 replies; 4+ messages in thread
From: Zhang Yi @ 2021-06-19 9:36 UTC (permalink / raw)
To: linux-block; +Cc: axboe, jbacik, yi.zhang, yukuai3
Now that we disable wbt by simply zero out rwb->wb_normal in
wbt_disable_default() when switch elevator to bfq, but it's not safe
because it will become false positive if we change queue depth. If it
become false positive between wbt_wait() and wbt_track() when submit
write request, it will lead to drop rqw->inflight to -1 in wbt_done(),
which will end up trigger IO hung. Fix this issue by introduce a new
state which mean the wbt was disabled.
Fixes: a79050434b45 ("blk-rq-qos: refactor out common elements of blk-wbt")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
block/blk-wbt.c | 5 +++--
block/blk-wbt.h | 1 +
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 42aed0160f86..b098ac6a84f0 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -77,7 +77,8 @@ enum {
static inline bool rwb_enabled(struct rq_wb *rwb)
{
- return rwb && rwb->wb_normal != 0;
+ return rwb && rwb->enable_state != WBT_STATE_OFF_DEFAULT &&
+ rwb->wb_normal != 0;
}
static void wb_timestamp(struct rq_wb *rwb, unsigned long *var)
@@ -702,7 +703,7 @@ void wbt_disable_default(struct request_queue *q)
rwb = RQWB(rqos);
if (rwb->enable_state == WBT_STATE_ON_DEFAULT) {
blk_stat_deactivate(rwb->cb);
- rwb->wb_normal = 0;
+ rwb->enable_state = WBT_STATE_OFF_DEFAULT;
}
}
EXPORT_SYMBOL_GPL(wbt_disable_default);
diff --git a/block/blk-wbt.h b/block/blk-wbt.h
index 16bdc85b8df9..2eb01becde8c 100644
--- a/block/blk-wbt.h
+++ b/block/blk-wbt.h
@@ -34,6 +34,7 @@ enum {
enum {
WBT_STATE_ON_DEFAULT = 1,
WBT_STATE_ON_MANUAL = 2,
+ WBT_STATE_OFF_DEFAULT
};
struct rq_wb {
--
2.31.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 2/2] blk-wbt: make sure throttle is enabled properly
2021-06-19 9:36 [PATCH 0/2] blk-wbt: fix two wbt enable problems Zhang Yi
2021-06-19 9:36 ` [PATCH 1/2] blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled() Zhang Yi
@ 2021-06-19 9:37 ` Zhang Yi
2021-06-21 16:07 ` [PATCH 0/2] blk-wbt: fix two wbt enable problems Jens Axboe
2 siblings, 0 replies; 4+ messages in thread
From: Zhang Yi @ 2021-06-19 9:37 UTC (permalink / raw)
To: linux-block; +Cc: axboe, jbacik, yi.zhang, yukuai3
After commit a79050434b45 ("blk-rq-qos: refactor out common elements of
blk-wbt"), if throttle was disabled by wbt_disable_default(), we could
not enable again, fix this by set enable_state back to
WBT_STATE_ON_DEFAULT.
Fixes: a79050434b45 ("blk-rq-qos: refactor out common elements of blk-wbt")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
block/blk-wbt.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index b098ac6a84f0..f5e5ac915bf7 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -637,9 +637,13 @@ void wbt_set_write_cache(struct request_queue *q, bool write_cache_on)
void wbt_enable_default(struct request_queue *q)
{
struct rq_qos *rqos = wbt_rq_qos(q);
+
/* Throttling already enabled? */
- if (rqos)
+ if (rqos) {
+ if (RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
+ RQWB(rqos)->enable_state = WBT_STATE_ON_DEFAULT;
return;
+ }
/* Queue not registered? Maybe shutting down... */
if (!blk_queue_registered(q))
--
2.31.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 0/2] blk-wbt: fix two wbt enable problems
2021-06-19 9:36 [PATCH 0/2] blk-wbt: fix two wbt enable problems Zhang Yi
2021-06-19 9:36 ` [PATCH 1/2] blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled() Zhang Yi
2021-06-19 9:37 ` [PATCH 2/2] blk-wbt: make sure throttle is enabled properly Zhang Yi
@ 2021-06-21 16:07 ` Jens Axboe
2 siblings, 0 replies; 4+ messages in thread
From: Jens Axboe @ 2021-06-21 16:07 UTC (permalink / raw)
To: Zhang Yi, linux-block; +Cc: jbacik, yukuai3
On 6/19/21 3:36 AM, Zhang Yi wrote:
> Commit a79050434b45 ("blk-rq-qos: refactor out common elements of
> blk-wbt") introduce two wbt enable problems. The first one will cause
> false positive check by rwb_enabled() and lead to IO hung, the second
> one is wbt_enable_default() could not re-enable wbt after switch
> elevator back from bfq to other one.
Applied, thanks.
--
Jens Axboe
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-06-21 16:07 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2021-06-19 9:36 [PATCH 0/2] blk-wbt: fix two wbt enable problems Zhang Yi
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2021-06-19 9:37 ` [PATCH 2/2] blk-wbt: make sure throttle is enabled properly Zhang Yi
2021-06-21 16:07 ` [PATCH 0/2] blk-wbt: fix two wbt enable problems Jens Axboe
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