block: add request submission interface

This patch adds blk_insert_cloned_request(), a generic request
submission interface for request stacking drivers.
Request-based dm will use it to submit their clones to underlying
devices.

blk_rq_check_limits() is also added because it is possible that
the lower queue has stronger limitations than the upper queue
if multiple drivers are stacking at request-level.
Not only for blk_insert_cloned_request()'s internal use, the function
will be used by request-based dm when the queue limitation is
modified (e.g. by replacing dm's table).

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Kiyoshi Ueda 2008-09-18 10:45:38 -04:00 committed by Jens Axboe
parent 32fab448e5
commit 82124d6035
2 changed files with 84 additions and 0 deletions

View File

@ -1529,6 +1529,87 @@ void submit_bio(int rw, struct bio *bio)
}
EXPORT_SYMBOL(submit_bio);
/**
* blk_rq_check_limits - Helper function to check a request for the queue limit
* @q: the queue
* @rq: the request being checked
*
* Description:
* @rq may have been made based on weaker limitations of upper-level queues
* in request stacking drivers, and it may violate the limitation of @q.
* Since the block layer and the underlying device driver trust @rq
* after it is inserted to @q, it should be checked against @q before
* the insertion using this generic function.
*
* This function should also be useful for request stacking drivers
* in some cases below, so export this fuction.
* Request stacking drivers like request-based dm may change the queue
* limits while requests are in the queue (e.g. dm's table swapping).
* Such request stacking drivers should check those requests agaist
* the new queue limits again when they dispatch those requests,
* although such checkings are also done against the old queue limits
* when submitting requests.
*/
int blk_rq_check_limits(struct request_queue *q, struct request *rq)
{
if (rq->nr_sectors > q->max_sectors ||
rq->data_len > q->max_hw_sectors << 9) {
printk(KERN_ERR "%s: over max size limit.\n", __func__);
return -EIO;
}
/*
* queue's settings related to segment counting like q->bounce_pfn
* may differ from that of other stacking queues.
* Recalculate it to check the request correctly on this queue's
* limitation.
*/
blk_recalc_rq_segments(rq);
if (rq->nr_phys_segments > q->max_phys_segments ||
rq->nr_phys_segments > q->max_hw_segments) {
printk(KERN_ERR "%s: over max segments limit.\n", __func__);
return -EIO;
}
return 0;
}
EXPORT_SYMBOL_GPL(blk_rq_check_limits);
/**
* blk_insert_cloned_request - Helper for stacking drivers to submit a request
* @q: the queue to submit the request
* @rq: the request being queued
*/
int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
{
unsigned long flags;
if (blk_rq_check_limits(q, rq))
return -EIO;
#ifdef CONFIG_FAIL_MAKE_REQUEST
if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
should_fail(&fail_make_request, blk_rq_bytes(rq)))
return -EIO;
#endif
spin_lock_irqsave(q->queue_lock, flags);
/*
* Submitting request must be dequeued before calling this function
* because it will be linked to another request_queue
*/
BUG_ON(blk_queued_rq(rq));
drive_stat_acct(rq, 1);
__elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
spin_unlock_irqrestore(q->queue_lock, flags);
return 0;
}
EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
/**
* __end_that_request_first - end I/O on a request
* @req: the request being processed

View File

@ -693,6 +693,9 @@ extern void __blk_put_request(struct request_queue *, struct request *);
extern struct request *blk_get_request(struct request_queue *, int, gfp_t);
extern void blk_insert_request(struct request_queue *, struct request *, int, void *);
extern void blk_requeue_request(struct request_queue *, struct request *);
extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);
extern int blk_insert_cloned_request(struct request_queue *q,
struct request *rq);
extern void blk_plug_device(struct request_queue *);
extern void blk_plug_device_unlocked(struct request_queue *);
extern int blk_remove_plug(struct request_queue *);