[PATCH 25/28] blk_end_request: add callback feature (take 3)
From: Kiyoshi Ueda <hidden>
Date: 2007-11-30 23:36:45
Also in:
dm-devel, linux-scsi, lkml
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 <redacted>
Signed-off-by: Jun'ichi Nomura <redacted>
---
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 *); /*