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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 12-11-2007, 09:51 PM
Kiyoshi Ueda
 
Default 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>
---
block/ll_rw_blk.c | 72 ++++++++++++++++++++++++++++++++++++++++++++-----
include/linux/blkdev.h | 2 +
2 files changed, 68 insertions(+), 6 deletions(-)

Index: 2.6.24-rc4/block/ll_rw_blk.c
================================================== =================
--- 2.6.24-rc4.orig/block/ll_rw_blk.c
+++ 2.6.24-rc4/block/ll_rw_blk.c
@@ -3803,10 +3803,14 @@ static void complete_request(struct requ
}

/**
- * 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.
@@ -3814,9 +3818,10 @@ static void complete_request(struct requ
*
* 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;
@@ -3833,6 +3838,10 @@ int blk_end_request(struct request *rq,
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);
@@ -3841,6 +3850,25 @@ int blk_end_request(struct request *rq,

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);

/**
@@ -3879,6 +3907,38 @@ int __blk_end_request(struct request *rq
}
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)
{
Index: 2.6.24-rc4/include/linux/blkdev.h
================================================== =================
--- 2.6.24-rc4.orig/include/linux/blkdev.h
+++ 2.6.24-rc4/include/linux/blkdev.h
@@ -736,6 +736,8 @@ extern void end_that_request_last(struct
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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