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authorYu Kuai <yukuai3@huawei.com>2022-09-13 18:57:49 +0800
committerJens Axboe <axboe@kernel.dk>2022-09-21 08:36:13 -0600
commit8c5035dfbb9475b67c82b3fdb7351236525bf52b (patch)
treeabcac6d89b9e248e7714ef76b1878b06ea33e346 /block
parentf7de4886fe8f008ac4f7beeacd9bedb6b91241f5 (diff)
blk-wbt: call rq_qos_add() after wb_normal is initialized
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>
Diffstat (limited to 'block')
-rw-r--r--block/blk-wbt.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index a9982000b667..246467926253 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -843,6 +843,10 @@ 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.
@@ -853,11 +857,6 @@ int wbt_init(struct request_queue *q)
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;
err_free: