* [PATCH 5.10 1/3] block: wbt: Remove unnecessary invoking of wbt_update_limits in wbt_init
2022-10-18 1:43 [PATCH 5.10 0/3] wbt stable patches Yu Kuai
@ 2022-10-18 1:43 ` Yu Kuai
2022-10-18 1:43 ` [PATCH 5.10 2/3] blk-wbt: call rq_qos_add() after wb_normal is initialized Yu Kuai
2022-10-18 1:43 ` [PATCH 5.10 3/3] blk-wbt: fix that 'rwb->wc' is always set to 1 in wbt_init() Yu Kuai
2 siblings, 0 replies; 7+ messages in thread
From: Yu Kuai @ 2022-10-18 1:43 UTC (permalink / raw)
To: gregkh, axboe, yukuai3
Cc: stable, linux-block, linux-kernel, yukuai1, yi.zhang
From: Lei Chen <lennychen@tencent.com>
commit 5a20d073ec54a72d9a732fa44bfe14954eb6332f upstream.
It's unnecessary to call wbt_update_limits explicitly within wbt_init,
because it will be called in the following function wbt_queue_depth_changed.
Signed-off-by: Lei Chen <lennychen@tencent.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
block/blk-wbt.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 35d81b5deae1..4ec0a018a2ad 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -840,7 +840,6 @@ int wbt_init(struct request_queue *q)
rwb->enable_state = WBT_STATE_ON_DEFAULT;
rwb->wc = 1;
rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
- wbt_update_limits(rwb);
/*
* Assign rwb and add the stats callback.
--
2.31.1
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH 5.10 2/3] blk-wbt: call rq_qos_add() after wb_normal is initialized
2022-10-18 1:43 [PATCH 5.10 0/3] wbt stable patches Yu Kuai
2022-10-18 1:43 ` [PATCH 5.10 1/3] block: wbt: Remove unnecessary invoking of wbt_update_limits in wbt_init Yu Kuai
@ 2022-10-18 1:43 ` Yu Kuai
2022-10-26 16:47 ` Greg KH
2022-10-18 1:43 ` [PATCH 5.10 3/3] blk-wbt: fix that 'rwb->wc' is always set to 1 in wbt_init() Yu Kuai
2 siblings, 1 reply; 7+ messages in thread
From: Yu Kuai @ 2022-10-18 1:43 UTC (permalink / raw)
To: gregkh, axboe, yukuai3
Cc: stable, linux-block, linux-kernel, yukuai1, yi.zhang
From: Yu Kuai <yukuai3@huawei.com>
commit 8c5035dfbb9475b67c82b3fdb7351236525bf52b upstream.
Our test found a problem that wbt inflight counter is negative, which
will cause io hang(noted that this problem doesn't exist in mainline):
t1: device create t2: issue io
add_disk
blk_register_queue
wbt_enable_default
wbt_init
rq_qos_add
// wb_normal is still 0
/*
* in mainline, disk can't be opened before
* bdev_add(), however, in old kernels, disk
* can be opened before blk_register_queue().
*/
blkdev_issue_flush
// disk size is 0, however, it's not checked
submit_bio_wait
submit_bio
blk_mq_submit_bio
rq_qos_throttle
wbt_wait
bio_to_wbt_flags
rwb_enabled
// wb_normal is 0, inflight is not increased
wbt_queue_depth_changed(&rwb->rqos);
wbt_update_limits
// wb_normal is initialized
rq_qos_track
wbt_track
rq->wbt_flags |= bio_to_wbt_flags(rwb, bio);
// wb_normal is not 0，wbt_flags will be set
t3: io completion
blk_mq_free_request
rq_qos_done
wbt_done
wbt_is_tracked
// return true
__wbt_done
wbt_rqw_done
atomic_dec_return(&rqw->inflight);
// inflight is decreased
commit 8235b5c1e8c1 ("block: call bdev_add later in device_add_disk") can
avoid this problem, however it's better to fix this problem in wbt:
1) Lower kernel can't backport this patch due to lots of refactor.
2) Root cause is that wbt call rq_qos_add() before wb_normal is
initialized.
Fixes: e34cbd307477 ("blk-wbt: add general throttling mechanism")
Cc: <stable@vger.kernel.org>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20220913105749.3086243-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-wbt.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 4ec0a018a2ad..bafdb8098893 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -840,6 +840,10 @@ int wbt_init(struct request_queue *q)
rwb->enable_state = WBT_STATE_ON_DEFAULT;
rwb->wc = 1;
rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
+ rwb->min_lat_nsec = wbt_default_latency_nsec(q);
+
+ wbt_queue_depth_changed(&rwb->rqos);
+ wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
/*
* Assign rwb and add the stats callback.
@@ -847,10 +851,5 @@ int wbt_init(struct request_queue *q)
rq_qos_add(q, &rwb->rqos);
blk_stat_add_callback(q, rwb->cb);
- rwb->min_lat_nsec = wbt_default_latency_nsec(q);
-
- wbt_queue_depth_changed(&rwb->rqos);
- wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
-
return 0;
}
--
2.31.1
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH 5.10 3/3] blk-wbt: fix that 'rwb->wc' is always set to 1 in wbt_init()
2022-10-18 1:43 [PATCH 5.10 0/3] wbt stable patches Yu Kuai
2022-10-18 1:43 ` [PATCH 5.10 1/3] block: wbt: Remove unnecessary invoking of wbt_update_limits in wbt_init Yu Kuai
2022-10-18 1:43 ` [PATCH 5.10 2/3] blk-wbt: call rq_qos_add() after wb_normal is initialized Yu Kuai
@ 2022-10-18 1:43 ` Yu Kuai
2 siblings, 0 replies; 7+ messages in thread
From: Yu Kuai @ 2022-10-18 1:43 UTC (permalink / raw)
To: gregkh, axboe, yukuai3
Cc: stable, linux-block, linux-kernel, yukuai1, yi.zhang
From: Yu Kuai <yukuai3@huawei.com>
commit 285febabac4a16655372d23ff43e89ff6f216691 upstream.
commit 8c5035dfbb94 ("blk-wbt: call rq_qos_add() after wb_normal is
initialized") moves wbt_set_write_cache() before rq_qos_add(), which
is wrong because wbt_rq_qos() is still NULL.
Fix the problem by removing wbt_set_write_cache() and setting 'rwb->wc'
directly. Noted that this patch also remove the redundant setting of
'rab->wc'.
Fixes: 8c5035dfbb94 ("blk-wbt: call rq_qos_add() after wb_normal is initialized")
Reported-by: kernel test robot <yujie.liu@intel.com>
Link: https://lore.kernel.org/r/202210081045.77ddf59b-yujie.liu@intel.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20221009101038.1692875-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-wbt.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index bafdb8098893..6f63920f073c 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -838,12 +838,11 @@ int wbt_init(struct request_queue *q)
rwb->last_comp = rwb->last_issue = jiffies;
rwb->win_nsec = RWB_WINDOW_NSEC;
rwb->enable_state = WBT_STATE_ON_DEFAULT;
- rwb->wc = 1;
+ rwb->wc = test_bit(QUEUE_FLAG_WC, &q->queue_flags);
rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
rwb->min_lat_nsec = wbt_default_latency_nsec(q);
wbt_queue_depth_changed(&rwb->rqos);
- wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
/*
* Assign rwb and add the stats callback.
--
2.31.1
^ permalink raw reply [flat|nested] 7+ messages in thread