This patch adds an interface to update request information so that
request stacking drivers can complete only data part of a request
without completing the request.
Request stacking drivers can use it for partial completion.
Request stacking drivers like request-based dm need to complete
clone requests from bottom to top on the device stack in that order.
If request stacking drivers use blk_end_request() to updatethe original
request during partial completion (in bio->bi_end_io() hook),
the original request will be completed before the clone request when
all bios are completed. It breaks the ordering.
blk_update_request() just completes only data part of a request and
updates information of the request, but doesn't complete the request.
Signed-off-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
---
block/blk-core.c | 59 +++++++++++++++++++++++++++++++++++++++++--------
include/linux/blkdev.h | 2 +
2 files changed, 52 insertions(+), 9 deletions(-)
Index: 2.6.25-rc5/block/blk-core.c
===================================================================
--- 2.6.25-rc5.orig/block/blk-core.c
+++ 2.6.25-rc5/block/blk-core.c
@@ -1853,6 +1853,22 @@ void end_request(struct request *req, in
}
EXPORT_SYMBOL(end_request);
+static int end_that_request_data(struct request *rq, int error,
+ unsigned int nr_bytes, unsigned int bidi_bytes)
+{
+ if (blk_fs_request(rq) || blk_pc_request(rq)) {
+ if (__end_that_request_first(rq, error, nr_bytes))
+ return 1;
+
+ /* Bidi request must be completed as a whole */
+ if (blk_bidi_rq(rq) &&
+ __end_that_request_first(rq->next_rq, error, bidi_bytes))
+ return 1;
+ }
+
+ return 0;
+}
+
/**
* blk_end_io - Generic end_io function to complete a request.
* @rq: the request being processed
@@ -1879,15 +1895,8 @@ static int blk_end_io(struct request *rq
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, error, nr_bytes))
- return 1;
-
- /* Bidi request must be completed as a whole */
- if (blk_bidi_rq(rq) &&
- __end_that_request_first(rq->next_rq, error, bidi_bytes))
- return 1;
- }
+ if (end_that_request_data(rq, error, nr_bytes, bidi_bytes))
+ return 1;
/* Special feature for tricky drivers */
if (drv_callback && drv_callback(rq))
@@ -1972,6 +1981,38 @@ int blk_end_bidi_request(struct request
EXPORT_SYMBOL_GPL(blk_end_bidi_request);
/**
+ * blk_update_request - Special helper function for request stacking drivers
+ * @rq: the request being processed
+ * @error: 0 for success, < 0 for error
+ * @nr_bytes: number of bytes to complete @rq
+ *
+ * Description:
+ * Ends I/O on a number of bytes attached to @rq, but doesn't complete
+ * the request structure even if @rq doesn't have leftover.
+ * If @rq has leftover, sets it up for the next range of segments.
+ *
+ * This special helper function is only for request stacking drivers
+ * (e.g. request-based dm) so that they can handle partial completion.
+ * Actual device drivers should use blk_end_request instead.
+ **/
+void blk_update_request(struct request *rq, int error, unsigned int nr_bytes)
+{
+ if (!end_that_request_data(rq, error, nr_bytes, 0)) {
+ /*
+ * All bios in the request have been completed.
+ * Then, members of the request are not updated.
+ * Update those members to avoid double charge of diskstat
+ * when the stacking driver calls blk_end_request()
+ * to complete the request actually.
+ */
+ rq->nr_sectors = rq->hard_nr_sectors = 0;
+ rq->current_nr_sectors = rq->hard_cur_sectors = 0;
+ rq->nr_phys_segments = rq->nr_hw_segments = 0;
+ }
+}
+EXPORT_SYMBOL_GPL(blk_update_request);
+
+/**
* blk_end_request_callback - Special helper function for tricky drivers
* @rq: the request being processed
* @error: 0 for success, < 0 for error
Index: 2.6.25-rc5/include/linux/blkdev.h
===================================================================
--- 2.6.25-rc5.orig/include/linux/blkdev.h
+++ 2.6.25-rc5/include/linux/blkdev.h
@@ -673,6 +673,8 @@ extern int blk_end_request_callback(stru
unsigned int nr_bytes,
int (drv_callback)(struct request *));
extern void blk_complete_request(struct request *);
+extern void blk_update_request(struct request *rq, int error,
+ unsigned int nr_bytes);
/*
* blk_end_request() takes bytes instead of sectors as a complete size.
--
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