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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: 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 2007-12-11 17:51:02 -05:00 committed by Jens Axboe
parent 5e36bb6ee8
commit e19a3ab058
2 changed files with 68 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
block/ll_rw_blk.c
View File

@ -3825,10 +3825,14 @@ static void complete_request(struct request *rq, int error)
}
/**
* 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
* 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)
{

2
include/linux/blkdev.h
View File

@ -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 *);
/*