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A NULL pointer crash was reported for the case of having the BFQ IO scheduler attached to the underlying blk-mq paths of a DM multipath device. The crash occured in blk_mq_sched_insert_request()'s call to e->type->ops.mq.insert_requests(). Paolo Valente correctly summarized why the crash occured with: "the call chain (dm_mq_queue_rq -> map_request -> setup_clone -> blk_rq_prep_clone) creates a cloned request without invoking e->type->ops.mq.prepare_request for the target elevator e. The cloned request is therefore not initialized for the scheduler, but it is however inserted into the scheduler by blk_mq_sched_insert_request." All said, a request-based DM multipath device's IO scheduler should be the only one used -- when the original requests are issued to the underlying paths as cloned requests they are inserted directly in the underlying dispatch queue(s) rather than through an additional elevator. But commitbd166ef18("blk-mq-sched: add framework for MQ capable IO schedulers") switched blk_insert_cloned_request() from using blk_mq_insert_request() to blk_mq_sched_insert_request(). Which incorrectly added elevator machinery into a call chain that isn't supposed to have any. To fix this introduce a blk-mq private blk_mq_request_bypass_insert() that blk_insert_cloned_request() calls to insert the request without involving any elevator that may be attached to the cloned request's request_queue. Fixes:bd166ef183("blk-mq-sched: add framework for MQ capable IO schedulers") Cc: stable@vger.kernel.org Reported-by: Bart Van Assche <Bart.VanAssche@wdc.com> Tested-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
141 lines
4.0 KiB
C
141 lines
4.0 KiB
C
#ifndef INT_BLK_MQ_H
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#define INT_BLK_MQ_H
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#include "blk-stat.h"
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struct blk_mq_tag_set;
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struct blk_mq_ctx {
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struct {
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spinlock_t lock;
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struct list_head rq_list;
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} ____cacheline_aligned_in_smp;
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unsigned int cpu;
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unsigned int index_hw;
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/* incremented at dispatch time */
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unsigned long rq_dispatched[2];
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unsigned long rq_merged;
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/* incremented at completion time */
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unsigned long ____cacheline_aligned_in_smp rq_completed[2];
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struct request_queue *queue;
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struct kobject kobj;
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} ____cacheline_aligned_in_smp;
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void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
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void blk_mq_freeze_queue(struct request_queue *q);
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void blk_mq_free_queue(struct request_queue *q);
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int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr);
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void blk_mq_wake_waiters(struct request_queue *q);
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bool blk_mq_dispatch_rq_list(struct request_queue *, struct list_head *);
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void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list);
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bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx);
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bool blk_mq_get_driver_tag(struct request *rq, struct blk_mq_hw_ctx **hctx,
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bool wait);
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/*
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* Internal helpers for allocating/freeing the request map
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*/
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void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
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unsigned int hctx_idx);
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void blk_mq_free_rq_map(struct blk_mq_tags *tags);
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struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
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unsigned int hctx_idx,
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unsigned int nr_tags,
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unsigned int reserved_tags);
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int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
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unsigned int hctx_idx, unsigned int depth);
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/*
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* Internal helpers for request insertion into sw queues
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*/
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void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
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bool at_head);
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void blk_mq_request_bypass_insert(struct request *rq);
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void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
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struct list_head *list);
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/*
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* CPU -> queue mappings
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*/
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extern int blk_mq_hw_queue_to_node(unsigned int *map, unsigned int);
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static inline struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q,
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int cpu)
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{
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return q->queue_hw_ctx[q->mq_map[cpu]];
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}
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/*
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* sysfs helpers
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*/
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extern void blk_mq_sysfs_init(struct request_queue *q);
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extern void blk_mq_sysfs_deinit(struct request_queue *q);
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extern int __blk_mq_register_dev(struct device *dev, struct request_queue *q);
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extern int blk_mq_sysfs_register(struct request_queue *q);
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extern void blk_mq_sysfs_unregister(struct request_queue *q);
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extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx);
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extern void blk_mq_rq_timed_out(struct request *req, bool reserved);
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void blk_mq_release(struct request_queue *q);
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static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
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unsigned int cpu)
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{
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return per_cpu_ptr(q->queue_ctx, cpu);
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}
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/*
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* This assumes per-cpu software queueing queues. They could be per-node
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* as well, for instance. For now this is hardcoded as-is. Note that we don't
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* care about preemption, since we know the ctx's are persistent. This does
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* mean that we can't rely on ctx always matching the currently running CPU.
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*/
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static inline struct blk_mq_ctx *blk_mq_get_ctx(struct request_queue *q)
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{
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return __blk_mq_get_ctx(q, get_cpu());
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}
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static inline void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
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{
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put_cpu();
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}
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struct blk_mq_alloc_data {
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/* input parameter */
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struct request_queue *q;
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unsigned int flags;
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unsigned int shallow_depth;
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/* input & output parameter */
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struct blk_mq_ctx *ctx;
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struct blk_mq_hw_ctx *hctx;
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};
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static inline struct blk_mq_tags *blk_mq_tags_from_data(struct blk_mq_alloc_data *data)
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{
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if (data->flags & BLK_MQ_REQ_INTERNAL)
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return data->hctx->sched_tags;
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return data->hctx->tags;
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}
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static inline bool blk_mq_hctx_stopped(struct blk_mq_hw_ctx *hctx)
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{
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return test_bit(BLK_MQ_S_STOPPED, &hctx->state);
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}
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static inline bool blk_mq_hw_queue_mapped(struct blk_mq_hw_ctx *hctx)
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{
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return hctx->nr_ctx && hctx->tags;
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}
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void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
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unsigned int inflight[2]);
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#endif
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