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![Yufen Yu](/assets/img/avatar_default.png)
We got a null pointer deference BUG_ON in blk_mq_rq_timed_out()
as following:
[ 108.825472] BUG: kernel NULL pointer dereference, address: 0000000000000040
[ 108.827059] PGD 0 P4D 0
[ 108.827313] Oops: 0000 [#1] SMP PTI
[ 108.827657] CPU: 6 PID: 198 Comm: kworker/6:1H Not tainted 5.3.0-rc8+ #431
[ 108.829503] Workqueue: kblockd blk_mq_timeout_work
[ 108.829913] RIP: 0010:blk_mq_check_expired+0x258/0x330
[ 108.838191] Call Trace:
[ 108.838406] bt_iter+0x74/0x80
[ 108.838665] blk_mq_queue_tag_busy_iter+0x204/0x450
[ 108.839074] ? __switch_to_asm+0x34/0x70
[ 108.839405] ? blk_mq_stop_hw_queue+0x40/0x40
[ 108.839823] ? blk_mq_stop_hw_queue+0x40/0x40
[ 108.840273] ? syscall_return_via_sysret+0xf/0x7f
[ 108.840732] blk_mq_timeout_work+0x74/0x200
[ 108.841151] process_one_work+0x297/0x680
[ 108.841550] worker_thread+0x29c/0x6f0
[ 108.841926] ? rescuer_thread+0x580/0x580
[ 108.842344] kthread+0x16a/0x1a0
[ 108.842666] ? kthread_flush_work+0x170/0x170
[ 108.843100] ret_from_fork+0x35/0x40
The bug is caused by the race between timeout handle and completion for
flush request.
When timeout handle function blk_mq_rq_timed_out() try to read
'req->q->mq_ops', the 'req' have completed and reinitiated by next
flush request, which would call blk_rq_init() to clear 'req' as 0.
After commit 12f5b93145
("blk-mq: Remove generation seqeunce"),
normal requests lifetime are protected by refcount. Until 'rq->ref'
drop to zero, the request can really be free. Thus, these requests
cannot been reused before timeout handle finish.
However, flush request has defined .end_io and rq->end_io() is still
called even if 'rq->ref' doesn't drop to zero. After that, the 'flush_rq'
can be reused by the next flush request handle, resulting in null
pointer deference BUG ON.
We fix this problem by covering flush request with 'rq->ref'.
If the refcount is not zero, flush_end_io() return and wait the
last holder recall it. To record the request status, we add a new
entry 'rq_status', which will be used in flush_end_io().
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: stable@vger.kernel.org # v4.18+
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
-------
v2:
- move rq_status from struct request to struct blk_flush_queue
v3:
- remove unnecessary '{}' pair.
v4:
- let spinlock to protect 'fq->rq_status'
v5:
- move rq_status after flush_running_idx member of struct blk_flush_queue
Signed-off-by: Jens Axboe <axboe@kernel.dk>
355 lines
11 KiB
C
355 lines
11 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef BLK_INTERNAL_H
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#define BLK_INTERNAL_H
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#include <linux/idr.h>
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#include <linux/blk-mq.h>
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#include <xen/xen.h>
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#include "blk-mq.h"
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#include "blk-mq-sched.h"
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/* Max future timer expiry for timeouts */
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#define BLK_MAX_TIMEOUT (5 * HZ)
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#ifdef CONFIG_DEBUG_FS
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extern struct dentry *blk_debugfs_root;
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#endif
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struct blk_flush_queue {
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unsigned int flush_queue_delayed:1;
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unsigned int flush_pending_idx:1;
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unsigned int flush_running_idx:1;
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blk_status_t rq_status;
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unsigned long flush_pending_since;
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struct list_head flush_queue[2];
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struct list_head flush_data_in_flight;
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struct request *flush_rq;
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/*
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* flush_rq shares tag with this rq, both can't be active
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* at the same time
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*/
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struct request *orig_rq;
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spinlock_t mq_flush_lock;
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};
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extern struct kmem_cache *blk_requestq_cachep;
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extern struct kobj_type blk_queue_ktype;
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extern struct ida blk_queue_ida;
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static inline struct blk_flush_queue *
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blk_get_flush_queue(struct request_queue *q, struct blk_mq_ctx *ctx)
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{
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return blk_mq_map_queue(q, REQ_OP_FLUSH, ctx)->fq;
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}
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static inline void __blk_get_queue(struct request_queue *q)
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{
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kobject_get(&q->kobj);
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}
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static inline bool
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is_flush_rq(struct request *req, struct blk_mq_hw_ctx *hctx)
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{
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return hctx->fq->flush_rq == req;
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}
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struct blk_flush_queue *blk_alloc_flush_queue(struct request_queue *q,
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int node, int cmd_size, gfp_t flags);
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void blk_free_flush_queue(struct blk_flush_queue *q);
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void blk_freeze_queue(struct request_queue *q);
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static inline void blk_queue_enter_live(struct request_queue *q)
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{
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/*
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* Given that running in generic_make_request() context
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* guarantees that a live reference against q_usage_counter has
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* been established, further references under that same context
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* need not check that the queue has been frozen (marked dead).
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*/
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percpu_ref_get(&q->q_usage_counter);
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}
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static inline bool biovec_phys_mergeable(struct request_queue *q,
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struct bio_vec *vec1, struct bio_vec *vec2)
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{
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unsigned long mask = queue_segment_boundary(q);
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phys_addr_t addr1 = page_to_phys(vec1->bv_page) + vec1->bv_offset;
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phys_addr_t addr2 = page_to_phys(vec2->bv_page) + vec2->bv_offset;
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if (addr1 + vec1->bv_len != addr2)
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return false;
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if (xen_domain() && !xen_biovec_phys_mergeable(vec1, vec2->bv_page))
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return false;
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if ((addr1 | mask) != ((addr2 + vec2->bv_len - 1) | mask))
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return false;
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return true;
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}
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static inline bool __bvec_gap_to_prev(struct request_queue *q,
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struct bio_vec *bprv, unsigned int offset)
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{
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return (offset & queue_virt_boundary(q)) ||
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((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
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}
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/*
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* Check if adding a bio_vec after bprv with offset would create a gap in
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* the SG list. Most drivers don't care about this, but some do.
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*/
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static inline bool bvec_gap_to_prev(struct request_queue *q,
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struct bio_vec *bprv, unsigned int offset)
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{
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if (!queue_virt_boundary(q))
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return false;
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return __bvec_gap_to_prev(q, bprv, offset);
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}
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static inline void blk_rq_bio_prep(struct request *rq, struct bio *bio,
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unsigned int nr_segs)
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{
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rq->nr_phys_segments = nr_segs;
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rq->__data_len = bio->bi_iter.bi_size;
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rq->bio = rq->biotail = bio;
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rq->ioprio = bio_prio(bio);
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if (bio->bi_disk)
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rq->rq_disk = bio->bi_disk;
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}
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#ifdef CONFIG_BLK_DEV_INTEGRITY
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void blk_flush_integrity(void);
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bool __bio_integrity_endio(struct bio *);
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static inline bool bio_integrity_endio(struct bio *bio)
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{
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if (bio_integrity(bio))
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return __bio_integrity_endio(bio);
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return true;
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}
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static inline bool integrity_req_gap_back_merge(struct request *req,
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struct bio *next)
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{
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struct bio_integrity_payload *bip = bio_integrity(req->bio);
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struct bio_integrity_payload *bip_next = bio_integrity(next);
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return bvec_gap_to_prev(req->q, &bip->bip_vec[bip->bip_vcnt - 1],
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bip_next->bip_vec[0].bv_offset);
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}
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static inline bool integrity_req_gap_front_merge(struct request *req,
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struct bio *bio)
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{
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struct bio_integrity_payload *bip = bio_integrity(bio);
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struct bio_integrity_payload *bip_next = bio_integrity(req->bio);
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return bvec_gap_to_prev(req->q, &bip->bip_vec[bip->bip_vcnt - 1],
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bip_next->bip_vec[0].bv_offset);
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}
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#else /* CONFIG_BLK_DEV_INTEGRITY */
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static inline bool integrity_req_gap_back_merge(struct request *req,
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struct bio *next)
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{
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return false;
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}
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static inline bool integrity_req_gap_front_merge(struct request *req,
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struct bio *bio)
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{
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return false;
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}
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static inline void blk_flush_integrity(void)
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{
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}
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static inline bool bio_integrity_endio(struct bio *bio)
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{
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return true;
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}
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#endif /* CONFIG_BLK_DEV_INTEGRITY */
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unsigned long blk_rq_timeout(unsigned long timeout);
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void blk_add_timer(struct request *req);
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bool bio_attempt_front_merge(struct request *req, struct bio *bio,
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unsigned int nr_segs);
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bool bio_attempt_back_merge(struct request *req, struct bio *bio,
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unsigned int nr_segs);
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bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
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struct bio *bio);
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bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
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unsigned int nr_segs, struct request **same_queue_rq);
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void blk_account_io_start(struct request *req, bool new_io);
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void blk_account_io_completion(struct request *req, unsigned int bytes);
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void blk_account_io_done(struct request *req, u64 now);
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/*
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* Internal elevator interface
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*/
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#define ELV_ON_HASH(rq) ((rq)->rq_flags & RQF_HASHED)
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void blk_insert_flush(struct request *rq);
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void elevator_init_mq(struct request_queue *q);
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int elevator_switch_mq(struct request_queue *q,
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struct elevator_type *new_e);
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void __elevator_exit(struct request_queue *, struct elevator_queue *);
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int elv_register_queue(struct request_queue *q, bool uevent);
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void elv_unregister_queue(struct request_queue *q);
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static inline void elevator_exit(struct request_queue *q,
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struct elevator_queue *e)
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{
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lockdep_assert_held(&q->sysfs_lock);
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blk_mq_sched_free_requests(q);
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__elevator_exit(q, e);
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}
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struct hd_struct *__disk_get_part(struct gendisk *disk, int partno);
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#ifdef CONFIG_FAIL_IO_TIMEOUT
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int blk_should_fake_timeout(struct request_queue *);
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ssize_t part_timeout_show(struct device *, struct device_attribute *, char *);
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ssize_t part_timeout_store(struct device *, struct device_attribute *,
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const char *, size_t);
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#else
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static inline int blk_should_fake_timeout(struct request_queue *q)
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{
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return 0;
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}
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#endif
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void __blk_queue_split(struct request_queue *q, struct bio **bio,
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unsigned int *nr_segs);
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int ll_back_merge_fn(struct request *req, struct bio *bio,
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unsigned int nr_segs);
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int ll_front_merge_fn(struct request *req, struct bio *bio,
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unsigned int nr_segs);
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struct request *attempt_back_merge(struct request_queue *q, struct request *rq);
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struct request *attempt_front_merge(struct request_queue *q, struct request *rq);
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int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
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struct request *next);
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unsigned int blk_recalc_rq_segments(struct request *rq);
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void blk_rq_set_mixed_merge(struct request *rq);
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bool blk_rq_merge_ok(struct request *rq, struct bio *bio);
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enum elv_merge blk_try_merge(struct request *rq, struct bio *bio);
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int blk_dev_init(void);
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/*
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* Contribute to IO statistics IFF:
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*
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* a) it's attached to a gendisk, and
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* b) the queue had IO stats enabled when this request was started, and
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* c) it's a file system request
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*/
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static inline bool blk_do_io_stat(struct request *rq)
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{
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return rq->rq_disk &&
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(rq->rq_flags & RQF_IO_STAT) &&
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!blk_rq_is_passthrough(rq);
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}
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static inline void req_set_nomerge(struct request_queue *q, struct request *req)
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{
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req->cmd_flags |= REQ_NOMERGE;
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if (req == q->last_merge)
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q->last_merge = NULL;
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}
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/*
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* The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size
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* is defined as 'unsigned int', meantime it has to aligned to with logical
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* block size which is the minimum accepted unit by hardware.
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*/
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static inline unsigned int bio_allowed_max_sectors(struct request_queue *q)
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{
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return round_down(UINT_MAX, queue_logical_block_size(q)) >> 9;
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}
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/*
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* Internal io_context interface
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*/
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void get_io_context(struct io_context *ioc);
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struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q);
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struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
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gfp_t gfp_mask);
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void ioc_clear_queue(struct request_queue *q);
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int create_task_io_context(struct task_struct *task, gfp_t gfp_mask, int node);
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/**
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* create_io_context - try to create task->io_context
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* @gfp_mask: allocation mask
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* @node: allocation node
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*
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* If %current->io_context is %NULL, allocate a new io_context and install
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* it. Returns the current %current->io_context which may be %NULL if
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* allocation failed.
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*
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* Note that this function can't be called with IRQ disabled because
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* task_lock which protects %current->io_context is IRQ-unsafe.
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*/
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static inline struct io_context *create_io_context(gfp_t gfp_mask, int node)
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{
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WARN_ON_ONCE(irqs_disabled());
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if (unlikely(!current->io_context))
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create_task_io_context(current, gfp_mask, node);
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return current->io_context;
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}
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/*
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* Internal throttling interface
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*/
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#ifdef CONFIG_BLK_DEV_THROTTLING
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extern void blk_throtl_drain(struct request_queue *q);
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extern int blk_throtl_init(struct request_queue *q);
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extern void blk_throtl_exit(struct request_queue *q);
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extern void blk_throtl_register_queue(struct request_queue *q);
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#else /* CONFIG_BLK_DEV_THROTTLING */
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static inline void blk_throtl_drain(struct request_queue *q) { }
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static inline int blk_throtl_init(struct request_queue *q) { return 0; }
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static inline void blk_throtl_exit(struct request_queue *q) { }
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static inline void blk_throtl_register_queue(struct request_queue *q) { }
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#endif /* CONFIG_BLK_DEV_THROTTLING */
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#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
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extern ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page);
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extern ssize_t blk_throtl_sample_time_store(struct request_queue *q,
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const char *page, size_t count);
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extern void blk_throtl_bio_endio(struct bio *bio);
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extern void blk_throtl_stat_add(struct request *rq, u64 time);
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#else
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static inline void blk_throtl_bio_endio(struct bio *bio) { }
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static inline void blk_throtl_stat_add(struct request *rq, u64 time) { }
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#endif
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#ifdef CONFIG_BOUNCE
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extern int init_emergency_isa_pool(void);
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extern void blk_queue_bounce(struct request_queue *q, struct bio **bio);
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#else
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static inline int init_emergency_isa_pool(void)
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{
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return 0;
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}
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static inline void blk_queue_bounce(struct request_queue *q, struct bio **bio)
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{
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}
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#endif /* CONFIG_BOUNCE */
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#ifdef CONFIG_BLK_CGROUP_IOLATENCY
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extern int blk_iolatency_init(struct request_queue *q);
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#else
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static inline int blk_iolatency_init(struct request_queue *q) { return 0; }
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#endif
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struct bio *blk_next_bio(struct bio *bio, unsigned int nr_pages, gfp_t gfp);
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#ifdef CONFIG_BLK_DEV_ZONED
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void blk_queue_free_zone_bitmaps(struct request_queue *q);
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#else
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static inline void blk_queue_free_zone_bitmaps(struct request_queue *q) {}
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#endif
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#endif /* BLK_INTERNAL_H */
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