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>

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>
Kiyoshi Ueda · Jens Axboe
1 parent 5e36bb6ee8
Showing 2 changed files with 68 additions and 6 deletions Side-by-side Diff
block/ll_rw_blk.c
include/linux/blkdev.h
@@ -3825,10 +3825,14 @@
 }
  
 /**
- * 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 @@
  *
  * 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 @@
 			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 @@
  
 	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);
  
 /**
@@ -3900,6 +3928,38 @@
 	return 0;
 }
 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)
@@ -734,6 +734,8 @@
 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 *);
  
 /*
...	...	@@ -3825,10 +3825,14 @@
3825	3825	}
3826	3826
3827	3827	/**
3828		- * blk_end_request - Helper function for drivers to complete the request.
3829		- * @rq: the request being processed
3830		- * @error: 0 for success, < 0 for error
3831		- * @nr_bytes: number of bytes to complete
	3828	+ * blk_end_io - Generic end_io function to complete a request.
	3829	+ * @rq: the request being processed
	3830	+ * @error: 0 for success, < 0 for error
	3831	+ * @nr_bytes: number of bytes to complete
	3832	+ * @drv_callback: function called between completion of bios in the request
	3833	+ * and completion of the request.
	3834	+ * If the callback returns non 0, this helper returns without
	3835	+ * completion of the request.
3832	3836	*
3833	3837	* Description:
3834	3838	* Ends I/O on a number of bytes attached to @rq.
3835	3839
...	...	@@ -3836,9 +3840,10 @@
3836	3840	*
3837	3841	* Return:
3838	3842	* 0 - we are done with this request
3839		- * 1 - still buffers pending for this request
	3843	+ * 1 - this request is not freed yet, it still has pending buffers.
3840	3844	**/
3841		-int blk_end_request(struct request *rq, int error, int nr_bytes)
	3845	+static int blk_end_io(struct request *rq, int error, int nr_bytes,
	3846	+ int (drv_callback)(struct request *))
3842	3847	{
3843	3848	struct request_queue *q = rq->q;
3844	3849	unsigned long flags = 0UL;
...	...	@@ -3855,6 +3860,10 @@
3855	3860	return 1;
3856	3861	}
3857	3862
	3863	+ /* Special feature for tricky drivers */
	3864	+ if (drv_callback && drv_callback(rq))
	3865	+ return 1;
	3866	+
3858	3867	add_disk_randomness(rq->rq_disk);
3859	3868
3860	3869	spin_lock_irqsave(q->queue_lock, flags);
...	...	@@ -3863,6 +3872,25 @@
3863	3872
3864	3873	return 0;
3865	3874	}
	3875	+
	3876	+/**
	3877	+ * blk_end_request - Helper function for drivers to complete the request.
	3878	+ * @rq: the request being processed
	3879	+ * @error: 0 for success, < 0 for error
	3880	+ * @nr_bytes: number of bytes to complete
	3881	+ *
	3882	+ * Description:
	3883	+ * Ends I/O on a number of bytes attached to @rq.
	3884	+ * If @rq has leftover, sets it up for the next range of segments.
	3885	+ *
	3886	+ * Return:
	3887	+ * 0 - we are done with this request
	3888	+ * 1 - still buffers pending for this request
	3889	+ **/
	3890	+int blk_end_request(struct request *rq, int error, int nr_bytes)
	3891	+{
	3892	+ return blk_end_io(rq, error, nr_bytes, NULL);
	3893	+}
3866	3894	EXPORT_SYMBOL_GPL(blk_end_request);
3867	3895
3868	3896	/**
...	...	@@ -3900,6 +3928,38 @@
3900	3928	return 0;
3901	3929	}
3902	3930	EXPORT_SYMBOL_GPL(__blk_end_request);
	3931	+
	3932	+/**
	3933	+ * blk_end_request_callback - Special helper function for tricky drivers
	3934	+ * @rq: the request being processed
	3935	+ * @error: 0 for success, < 0 for error
	3936	+ * @nr_bytes: number of bytes to complete
	3937	+ * @drv_callback: function called between completion of bios in the request
	3938	+ * and completion of the request.
	3939	+ * If the callback returns non 0, this helper returns without
	3940	+ * completion of the request.
	3941	+ *
	3942	+ * Description:
	3943	+ * Ends I/O on a number of bytes attached to @rq.
	3944	+ * If @rq has leftover, sets it up for the next range of segments.
	3945	+ *
	3946	+ * This special helper function is used only for existing tricky drivers.
	3947	+ * (e.g. cdrom_newpc_intr() of ide-cd)
	3948	+ * This interface will be removed when such drivers are rewritten.
	3949	+ * Don't use this interface in other places anymore.
	3950	+ *
	3951	+ * Return:
	3952	+ * 0 - we are done with this request
	3953	+ * 1 - this request is not freed yet.
	3954	+ * this request still has pending buffers or
	3955	+ * the driver doesn't want to finish this request yet.
	3956	+ **/
	3957	+int blk_end_request_callback(struct request *rq, int error, int nr_bytes,
	3958	+ int (drv_callback)(struct request *))
	3959	+{
	3960	+ return blk_end_io(rq, error, nr_bytes, drv_callback);
	3961	+}
	3962	+EXPORT_SYMBOL_GPL(blk_end_request_callback);
3903	3963
3904	3964	static void blk_rq_bio_prep(struct request_queue q, struct request rq,
3905	3965	struct bio *bio)
...	...	@@ -734,6 +734,8 @@
734	734	extern void end_request(struct request *, int);
735	735	extern void end_queued_request(struct request *, int);
736	736	extern void end_dequeued_request(struct request *, int);
	737	+extern int blk_end_request_callback(struct request *rq, int error, int nr_bytes,
	738	+ int (drv_callback)(struct request *));
737	739	extern void blk_complete_request(struct request *);
738	740
739	741	/*