From fd2ef39cc9a6b9c4c41864ac506906c52f94b06a Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 23 Jun 2021 11:36:34 +0200 Subject: blk: Fix lock inversion between ioc lock and bfqd lock Lockdep complains about lock inversion between ioc->lock and bfqd->lock: bfqd -> ioc: put_io_context+0x33/0x90 -> ioc->lock grabbed blk_mq_free_request+0x51/0x140 blk_put_request+0xe/0x10 blk_attempt_req_merge+0x1d/0x30 elv_attempt_insert_merge+0x56/0xa0 blk_mq_sched_try_insert_merge+0x4b/0x60 bfq_insert_requests+0x9e/0x18c0 -> bfqd->lock grabbed blk_mq_sched_insert_requests+0xd6/0x2b0 blk_mq_flush_plug_list+0x154/0x280 blk_finish_plug+0x40/0x60 ext4_writepages+0x696/0x1320 do_writepages+0x1c/0x80 __filemap_fdatawrite_range+0xd7/0x120 sync_file_range+0xac/0xf0 ioc->bfqd: bfq_exit_icq+0xa3/0xe0 -> bfqd->lock grabbed put_io_context_active+0x78/0xb0 -> ioc->lock grabbed exit_io_context+0x48/0x50 do_exit+0x7e9/0xdd0 do_group_exit+0x54/0xc0 To avoid this inversion we change blk_mq_sched_try_insert_merge() to not free the merged request but rather leave that upto the caller similarly to blk_mq_sched_try_merge(). And in bfq_insert_requests() we make sure to free all the merged requests after dropping bfqd->lock. Fixes: aee69d78dec0 ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler") Reviewed-by: Ming Lei Acked-by: Paolo Valente Signed-off-by: Jan Kara Link: https://lore.kernel.org/r/20210623093634.27879-3-jack@suse.cz Signed-off-by: Jens Axboe --- block/bfq-iosched.c | 6 ++++-- block/blk-merge.c | 19 ++++++++----------- block/blk-mq-sched.c | 5 +++-- block/blk-mq-sched.h | 3 ++- block/blk-mq.h | 11 +++++++++++ block/blk.h | 2 +- block/elevator.c | 11 ++++++++--- block/mq-deadline-main.c | 5 ++++- 8 files changed, 41 insertions(+), 21 deletions(-) (limited to 'block') diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 9433d38e486c..727955918563 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2345,9 +2345,9 @@ static bool bfq_bio_merge(struct request_queue *q, struct bio *bio, ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free); + spin_unlock_irq(&bfqd->lock); if (free) blk_mq_free_request(free); - spin_unlock_irq(&bfqd->lock); return ret; } @@ -5969,14 +5969,16 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, struct bfq_queue *bfqq; bool idle_timer_disabled = false; unsigned int cmd_flags; + LIST_HEAD(free); #ifdef CONFIG_BFQ_GROUP_IOSCHED if (!cgroup_subsys_on_dfl(io_cgrp_subsys) && rq->bio) bfqg_stats_update_legacy_io(q, rq); #endif spin_lock_irq(&bfqd->lock); - if (blk_mq_sched_try_insert_merge(q, rq)) { + if (blk_mq_sched_try_insert_merge(q, rq, &free)) { spin_unlock_irq(&bfqd->lock); + blk_mq_free_requests(&free); return; } diff --git a/block/blk-merge.c b/block/blk-merge.c index 4d97fb6dd226..1398b52a24b4 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -846,18 +846,15 @@ static struct request *attempt_front_merge(struct request_queue *q, return NULL; } -int blk_attempt_req_merge(struct request_queue *q, struct request *rq, - struct request *next) +/* + * Try to merge 'next' into 'rq'. Return true if the merge happened, false + * otherwise. The caller is responsible for freeing 'next' if the merge + * happened. + */ +bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, + struct request *next) { - struct request *free; - - free = attempt_merge(q, rq, next); - if (free) { - blk_put_request(free); - return 1; - } - - return 0; + return attempt_merge(q, rq, next); } bool blk_rq_merge_ok(struct request *rq, struct bio *bio) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 2403a5c2b053..c838d81ac058 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -399,9 +399,10 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio, return ret; } -bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq) +bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq, + struct list_head *free) { - return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq); + return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq, free); } EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge); diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h index aff037cfd8e7..5246ae040704 100644 --- a/block/blk-mq-sched.h +++ b/block/blk-mq-sched.h @@ -13,7 +13,8 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs, struct request **merged_request); bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs); -bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq); +bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq, + struct list_head *free); void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx); void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx); diff --git a/block/blk-mq.h b/block/blk-mq.h index 4b1ca7b7bbeb..d08779f77a26 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -302,6 +302,17 @@ static inline struct blk_plug *blk_mq_plug(struct request_queue *q, return NULL; } +/* Free all requests on the list */ +static inline void blk_mq_free_requests(struct list_head *list) +{ + while (!list_empty(list)) { + struct request *rq = list_entry_rq(list->next); + + list_del_init(&rq->queuelist); + blk_mq_free_request(rq); + } +} + /* * For shared tag users, we track the number of currently active users * and attempt to provide a fair share of the tag depth for each of them. diff --git a/block/blk.h b/block/blk.h index 4fcd7a032377..4b885c0f6708 100644 --- a/block/blk.h +++ b/block/blk.h @@ -224,7 +224,7 @@ ssize_t part_timeout_store(struct device *, struct device_attribute *, void __blk_queue_split(struct bio **bio, unsigned int *nr_segs); int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs); -int blk_attempt_req_merge(struct request_queue *q, struct request *rq, +bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, struct request *next); unsigned int blk_recalc_rq_segments(struct request *rq); void blk_rq_set_mixed_merge(struct request *rq); diff --git a/block/elevator.c b/block/elevator.c index 85d0d4adbb64..52ada14cfe45 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -350,9 +350,11 @@ enum elv_merge elv_merge(struct request_queue *q, struct request **req, * we can append 'rq' to an existing request, so we can throw 'rq' away * afterwards. * - * Returns true if we merged, false otherwise + * Returns true if we merged, false otherwise. 'free' will contain all + * requests that need to be freed. */ -bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) +bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq, + struct list_head *free) { struct request *__rq; bool ret; @@ -363,8 +365,10 @@ bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) /* * First try one-hit cache. */ - if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) + if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) { + list_add(&rq->queuelist, free); return true; + } if (blk_queue_noxmerges(q)) return false; @@ -378,6 +382,7 @@ bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) if (!__rq || !blk_attempt_req_merge(q, __rq, rq)) break; + list_add(&rq->queuelist, free); /* The merged request could be merged with others, try again */ ret = true; rq = __rq; diff --git a/block/mq-deadline-main.c b/block/mq-deadline-main.c index 4815e536091f..9db6da9ef4c6 100644 --- a/block/mq-deadline-main.c +++ b/block/mq-deadline-main.c @@ -719,6 +719,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, struct dd_per_prio *per_prio; enum dd_prio prio; struct dd_blkcg *blkcg; + LIST_HEAD(free); lockdep_assert_held(&dd->lock); @@ -742,8 +743,10 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, WARN_ON_ONCE(rq->elv.priv[0]); rq->elv.priv[0] = blkcg; - if (blk_mq_sched_try_insert_merge(q, rq)) + if (blk_mq_sched_try_insert_merge(q, rq, &free)) { + blk_mq_free_requests(&free); return; + } trace_block_rq_insert(rq); -- cgit