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blk-mq: rework flush sequencing logic

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Witch to using a preallocated flush_rq for blk-mq similar to what's done
with the old request path.  This allows us to set up the request properly
with a tag from the actually allowed range and ->rq_disk as needed by
some drivers.  To make life easier we also switch to dynamic allocation
of ->flush_rq for the old path.

This effectively reverts most of

    "blk-mq: fix for flush deadlock"

and

    "blk-mq: Don't reserve a tag for flush request"

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig 2014-02-10 09:29:00 -07:00 • committed by Jens Axboe
parent ce2c350b2c
commit 18741986a4
7 changed files with 76 additions and 117 deletions
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5
include/linux/blk-mq.h
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@ -36,15 +36,12 @@ struct blk_mq_hw_ctx {
struct list_head page_list;
struct blk_mq_tags *tags;
atomic_t pending_flush;
unsigned long queued;
unsigned long run;
#define BLK_MQ_MAX_DISPATCH_ORDER 10
unsigned long dispatched[BLK_MQ_MAX_DISPATCH_ORDER];
unsigned int queue_depth;
unsigned int reserved_tags;
unsigned int numa_node;
unsigned int cmd_size; /* per-request extra data */
@ -129,7 +126,7 @@ void blk_mq_insert_request(struct request_queue *, struct request *,
void blk_mq_run_queues(struct request_queue *q, bool async);
void blk_mq_free_request(struct request *rq);
bool blk_mq_can_queue(struct blk_mq_hw_ctx *);
struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp, bool reserved);
struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp);
struct request *blk_mq_alloc_reserved_request(struct request_queue *q, int rw, gfp_t gfp);
struct request *blk_mq_rq_from_tag(struct request_queue *q, unsigned int tag);