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[dm-devel] [PATCH 5/7] blk_end_request: change ide-cd (cdrom_newpc_intr)



This patch changes ide-cd (cdrom_newpc_intr) to use blk_end_request().
Due to the addness of the driver, the patch adds a variant of
the interface, blk_end_request_callback().

cdrom_newpc_intr() of ide-cd is the only function in the kernel tree
which needs to call end_that_request_first() and
end_that_request_last() separately.
blk_end_request_callback() allows it to pass callback function to do
something between end_that_request_first() and end_that_request_last().

ide-cd (cdrom_newpc_intr) needs to the followings:
  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 blk_end_request() has to return without completing request even if
no leftover in the 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      |   47 +++++++++++++++++++++++++++--
 drivers/ide/ide-cd.c   |   78 ++++++++++++++++++++++++++++++++++++++----------- include/linux/blkdev.h |    3 +
 3 files changed, 108 insertions(+), 20 deletions(-)

diff -rupN 04-other-caller-change/block/ll_rw_blk.c 05-ide-cd-change/block/ll_rw_blk.c
--- 04-other-caller-change/block/ll_rw_blk.c	2007-08-23 17:51:33.000000000 -0400
+++ 05-ide-cd-change/block/ll_rw_blk.c	2007-08-24 12:11:02.000000000 -0400
@@ -3671,6 +3671,10 @@ EXPORT_SYMBOL(end_request);
  * @nr_bytes:     number of bytes to complete
  * @needlock:     1 for queue lock need to be held.
  *                0 for queue lock held already.
+ * @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.
@@ -3681,7 +3685,8 @@ EXPORT_SYMBOL(end_request);
  *     1 - this request is not freed yet, it still has pending buffers.
  **/
 static int ____blk_end_request(struct request *rq, int uptodate, int nr_bytes,
-			       int needlock)
+			       int needlock,
+			       int (drv_callback)(struct request *))
 {
 	struct request_queue *q = rq->q;
 	unsigned long flags = 0UL;
@@ -3691,6 +3696,10 @@ static int ____blk_end_request(struct re
 			return 1;
 	}
 
+	/* Special feature for drivers/ide/ide-cd.c:cdrom_newpc_intr() */
+	if (drv_callback && drv_callback(rq))
+		return 1;
+
 	/*
 	 * No need to check the argument here because it is done
 	 * in add_disk_randomness().
@@ -3730,7 +3739,7 @@ static int ____blk_end_request(struct re
  **/
 int blk_end_request(struct request *rq, int uptodate, int nr_bytes)
 {
-	return ____blk_end_request(rq, uptodate, nr_bytes, 1);
+	return ____blk_end_request(rq, uptodate, nr_bytes, 1, NULL);
 }
 EXPORT_SYMBOL_GPL(blk_end_request);
 
@@ -3742,10 +3751,42 @@ EXPORT_SYMBOL_GPL(blk_end_request);
  **/
 int __blk_end_request(struct request *rq, int uptodate, int nr_bytes)
 {
-	return ____blk_end_request(rq, uptodate, nr_bytes, 0);
+	return ____blk_end_request(rq, uptodate, nr_bytes, 0, NULL);
 }
 EXPORT_SYMBOL_GPL(__blk_end_request);
 
+/**
+ * blk_end_request_callback - Special helper function for the ide-cd driver
+ * @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 for the ide-cd driver is used
+ *     to complete the request only in cdrom_newpc_intr().
+ *     This interface will be removed when cdrom_newpc_intr() is rewritten.
+ *     Don't use this interface in other places.
+ *
+ * Return:
+ *     0 - we are done with this request
+ *     1 - this request is not freed yet.
+ *         this request still has pending buffers or
+ *         the ide-cd 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 *))
+{
+	return ____blk_end_request(rq, uptodate, nr_bytes, 1, drv_callback);
+}
+EXPORT_SYMBOL_GPL(blk_end_request_callback);
+
 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
 		     struct bio *bio)
 {
diff -rupN 04-other-caller-change/drivers/ide/ide-cd.c 05-ide-cd-change/drivers/ide/ide-cd.c
--- 04-other-caller-change/drivers/ide/ide-cd.c	2007-08-23 17:51:33.000000000 -0400
+++ 05-ide-cd-change/drivers/ide/ide-cd.c	2007-08-24 12:14:54.000000000 -0400
@@ -1675,6 +1675,37 @@ static void post_transform_command(struc
 	}
 }
 
+/*
+ * Called from blk_end_request_callback() after the data of the request
+ * is completed and before the request is completed.
+ */
+static int cdrom_newpc_intr_dma_cb(struct request *rq)
+{
+	ide_drive_t *drive = rq->q->queuedata;
+	spinlock_t *ide_lock = rq->q->queue_lock;
+	unsigned long flags = 0UL;
+
+	rq->data_len = 0;
+	post_transform_command(rq);
+
+	spin_lock_irqsave(ide_lock, flags);
+	HWGROUP(drive)->rq = NULL;
+	spin_unlock_irqrestore(ide_lock, flags);
+
+	return 0;
+}
+
+/*
+ * Called from blk_end_request_callback() after the data of the request
+ * is completed and before the request is completed.
+ * By returning value '1', blk_end_request_callback() returns immediately
+ * without completing the request.
+ */
+static int cdrom_newpc_intr_dummy_cb(struct request *rq)
+{
+	return 1;
+}
+
 typedef void (xfer_func_t)(ide_drive_t *, void *, u32);
 
 /*
@@ -1713,9 +1744,16 @@ static ide_startstop_t cdrom_newpc_intr(
 			return ide_error(drive, "dma error", stat);
 		}
 
-		end_that_request_chunk(rq, 1, rq->data_len);
-		rq->data_len = 0;
-		goto end_request;
+		/*
+		 * post_transform_command() needs to be called after
+		 * the data of the request is completed, since it may
+		 * modify the data area of the request.
+		 * So use the callback special feature of blk_end_request().
+		 */
+		if (blk_end_request_callback(rq, 1, rq->data_len,
+					     cdrom_newpc_intr_dma_cb))
+			BUG();
+		return ide_stopped;
 	}
 
 	/*
@@ -1733,8 +1771,18 @@ static ide_startstop_t cdrom_newpc_intr(
 	/*
 	 * If DRQ is clear, the command has completed.
 	 */
-	if ((stat & DRQ_STAT) == 0)
-		goto end_request;
+	if ((stat & DRQ_STAT) == 0) {
+		if (!rq->data_len)
+			post_transform_command(rq);
+
+		spin_lock_irqsave(&ide_lock, flags);
+		if (__blk_end_request(rq, 1, 0))
+			BUG();
+		HWGROUP(drive)->rq = NULL;
+		spin_unlock_irqrestore(&ide_lock, flags);
+
+		return ide_stopped;
+	}
 
 	/*
 	 * check which way to transfer data
@@ -1787,7 +1835,14 @@ static ide_startstop_t cdrom_newpc_intr(
 		rq->data_len -= blen;
 
 		if (rq->bio)
-			end_that_request_chunk(rq, 1, blen);
+			/*
+	 		 * The request can't be completed until DRQ is cleared.
+			 * So complete the data, but don't complete the request
+			 * using the dummy function for the callback feature
+			 * of blk_end_request().
+			 */
+			blk_end_request_callback(rq, 1, blen,
+						 cdrom_newpc_intr_dummy_cb);
 		else
 			rq->data += blen;
 	}
@@ -1808,17 +1863,6 @@ static ide_startstop_t cdrom_newpc_intr(
 
 	ide_set_handler(drive, cdrom_newpc_intr, rq->timeout, NULL);
 	return ide_started;
-
-end_request:
-	if (!rq->data_len)
-		post_transform_command(rq);
-
-	spin_lock_irqsave(&ide_lock, flags);
-	blkdev_dequeue_request(rq);
-	end_that_request_last(rq, 1);
-	HWGROUP(drive)->rq = NULL;
-	spin_unlock_irqrestore(&ide_lock, flags);
-	return ide_stopped;
 }
 
 static ide_startstop_t cdrom_write_intr(ide_drive_t *drive)
diff -rupN 04-other-caller-change/include/linux/blkdev.h 05-ide-cd-change/include/linux/blkdev.h
--- 04-other-caller-change/include/linux/blkdev.h	2007-08-23 17:25:59.000000000 -0400
+++ 05-ide-cd-change/include/linux/blkdev.h	2007-08-24 12:21:45.000000000 -0400
@@ -734,6 +734,9 @@ extern int end_that_request_first(struct
 extern int end_that_request_chunk(struct request *, int, int);
 extern void end_that_request_last(struct request *, int);
 extern void end_request(struct request *req, int uptodate);
+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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