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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 11-30-2007, 10:34 PM
Kiyoshi Ueda
 
Default blk_end_request: add callback feature (take 3)

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

There are 2 drivers which need to do special works between
end_that_request_first() and end_that_request_last():
ide-cd and scsi bidi.

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 should/will be removed, after the drivers remove
such tricky behaviors.

o ide-cd (cdrom_newpc_intr())
cdrom_newpc_intr() needs to:
1. call post_transform_command() to modify request contents
2. wait completing request until DRQ_STAT is cleared
after end_that_request_first() and before end_that_request_last().

As for the second one, ide-cd will wait for the interrupt from device.
So end_that_request_first() and end_that_request_last() are called
separately in ide-cd.
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.

o scsi mid-layer for bidi request (scsi_end_bidi_request())
Bidi sets its specific value to rq->data_len before the request is
completed so that upper-layer can read it.
This setting must be between end_that_request_chunk() and
end_that_request_last(), because rq->data_len may be used
in end_that_request_chunk() by blk_trace and so on.

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 | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/blkdev.h | 3 ++
2 files changed, 53 insertions(+)

Index: 2.6.24-rc3-mm2/block/ll_rw_blk.c
================================================== =================
--- 2.6.24-rc3-mm2.orig/block/ll_rw_blk.c
+++ 2.6.24-rc3-mm2/block/ll_rw_blk.c
@@ -3850,6 +3850,56 @@ 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
+ * @uptodate: 1 for success, 0 for I/O error, < 0 for specific 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 uptodate, int nr_bytes,
+ int (drv_callback)(struct request *))
+{
+ struct request_queue *q = rq->q;
+ unsigned long flags = 0UL;
+
+ if (blk_fs_request(rq) || blk_pc_request(rq)) {
+ if (__end_that_request_first(rq, uptodate, 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);
+ complete_request(rq, uptodate);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+
+ return 0;
+}
+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-rc3-mm2/include/linux/blkdev.h
================================================== =================
--- 2.6.24-rc3-mm2.orig/include/linux/blkdev.h
+++ 2.6.24-rc3-mm2/include/linux/blkdev.h
@@ -733,6 +733,9 @@ 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 uptodate,
+ int nr_bytes,
+ int (drv_callback)(struct request *));
extern void blk_complete_request(struct request *);

/*

--
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