Commit e19a3ab0 authored by Kiyoshi Ueda's avatar Kiyoshi Ueda Committed by Jens Axboe
Browse files

blk_end_request: add callback feature (take 4) 



This patch adds a variant of the interface, blk_end_request_callback(),
which has driver callback feature.

Drivers may need to do special works between end_that_request_first()
and end_that_request_last().
For such drivers, blk_end_request_callback() allows it to pass
a callback function which is called between end_that_request_first()
and end_that_request_last().

This interface is only for fallback of other blk_end_request interfaces.
Drivers should avoid their tricky behaviors and use other interfaces
as much as possible.

Currently, only one driver, ide-cd, needs this interface.
So this interface should/will be removed, after the driver removes
such tricky behaviors.

o ide-cd (cdrom_newpc_intr())
  In PIO mode, cdrom_newpc_intr() needs to defer end_that_request_last()
  until the device clears DRQ_STAT and raises an interrupt after
  end_that_request_first().
  So end_that_request_first() and end_that_request_last() are called
  separately in cdrom_newpc_intr().

  This means blk_end_request_callback() has to return without
  completing request even if no leftover in the request.
  To satisfy the requirement, callback function has return value
  so that drivers can tell blk_end_request_callback() to return
  without completing request.

Signed-off-by: default avatarKiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 5e36bb6e

block/ll_rw_blk.c

+66 −6
Original line number Diff line number Diff line
@@ -3825,10 +3825,14 @@ static void complete_request(struct request *rq, int error) 
}



/**

 * blk_end_request - Helper function for drivers to complete the request.

 * blk_end_io - Generic end_io function to complete a request.

 * @rq:           the request being processed

 * @error:        0 for success, < 0 for error

 * @nr_bytes:     number of bytes to complete

 * @drv_callback: function called between completion of bios in the request

 *                and completion of the request.

 *                If the callback returns non 0, this helper returns without

 *                completion of the request.

 *

 * Description:

 *     Ends I/O on a number of bytes attached to @rq.
@@ -3836,9 +3840,10 @@ static void complete_request(struct request *rq, int error) 
 *

 * Return:

 *     0 - we are done with this request

 *     1 - still buffers pending for this request

 *     1 - this request is not freed yet, it still has pending buffers.

 **/

int blk_end_request(struct request *rq, int error, int nr_bytes)

static int blk_end_io(struct request *rq, int error, int nr_bytes,

		      int (drv_callback)(struct request *))

{

	struct request_queue *q = rq->q;

	unsigned long flags = 0UL;
@@ -3855,6 +3860,10 @@ int blk_end_request(struct request *rq, int error, int nr_bytes) 
			return 1;

	}



	/* Special feature for tricky drivers */

	if (drv_callback && drv_callback(rq))

		return 1;



	add_disk_randomness(rq->rq_disk);



	spin_lock_irqsave(q->queue_lock, flags);
@@ -3863,6 +3872,25 @@ int blk_end_request(struct request *rq, int error, int nr_bytes) 


	return 0;

}



/**

 * blk_end_request - Helper function for drivers to complete the request.

 * @rq:       the request being processed

 * @error:    0 for success, < 0 for error

 * @nr_bytes: number of bytes to complete

 *

 * Description:

 *     Ends I/O on a number of bytes attached to @rq.

 *     If @rq has leftover, sets it up for the next range of segments.

 *

 * Return:

 *     0 - we are done with this request

 *     1 - still buffers pending for this request

 **/

int blk_end_request(struct request *rq, int error, int nr_bytes)

{

	return blk_end_io(rq, error, nr_bytes, NULL);

}

EXPORT_SYMBOL_GPL(blk_end_request);



/**
@@ -3901,6 +3929,38 @@ int __blk_end_request(struct request *rq, int error, int nr_bytes) 
}

EXPORT_SYMBOL_GPL(__blk_end_request);



/**

 * blk_end_request_callback - Special helper function for tricky drivers

 * @rq:           the request being processed

 * @error:        0 for success, < 0 for error

 * @nr_bytes:     number of bytes to complete

 * @drv_callback: function called between completion of bios in the request

 *                and completion of the request.

 *                If the callback returns non 0, this helper returns without

 *                completion of the request.

 *

 * Description:

 *     Ends I/O on a number of bytes attached to @rq.

 *     If @rq has leftover, sets it up for the next range of segments.

 *

 *     This special helper function is used only for existing tricky drivers.

 *     (e.g. cdrom_newpc_intr() of ide-cd)

 *     This interface will be removed when such drivers are rewritten.

 *     Don't use this interface in other places anymore.

 *

 * Return:

 *     0 - we are done with this request

 *     1 - this request is not freed yet.

 *         this request still has pending buffers or

 *         the driver doesn't want to finish this request yet.

 **/

int blk_end_request_callback(struct request *rq, int error, int nr_bytes,

			     int (drv_callback)(struct request *))

{

	return blk_end_io(rq, error, nr_bytes, drv_callback);

}

EXPORT_SYMBOL_GPL(blk_end_request_callback);



static void blk_rq_bio_prep(struct request_queue *q, struct request *rq,

			    struct bio *bio)

{

include/linux/blkdev.h

+2 −0
Original line number Diff line number Diff line
@@ -734,6 +734,8 @@ extern void end_that_request_last(struct request *, int); 
extern void end_request(struct request *, int);

extern void end_queued_request(struct request *, int);

extern void end_dequeued_request(struct request *, int);

extern int blk_end_request_callback(struct request *rq, int error, int nr_bytes,

				    int (drv_callback)(struct request *));

extern void blk_complete_request(struct request *);



/*

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