block: add request update interface
This patch adds blk_update_request(), which updates struct request with completing its data part, but doesn't complete the struct request itself. Though it looks like end_that_request_first() of older kernels, blk_update_request() should be used only by request stacking drivers. Request-based dm will use it in bio->bi_end_io callback to update the original request when a data part of a cloned request completes. Followings are additional background information of why request-based dm needs this interface. - Request stacking drivers can't use blk_end_request() directly from the lower driver's completion context (bio->bi_end_io or rq->end_io), because some device drivers (e.g. ide) may try to complete their request with queue lock held, and it may cause deadlock. See below for detailed description of possible deadlock: <http://marc.info/?l=linux-kernel&m=120311479108569&w=2> - To solve that, request-based dm offloads the completion of cloned struct request to softirq context (i.e. using blk_complete_request() from rq->end_io). - Though it is possible to use the same solution from bio->bi_end_io, it will delay the notification of bio completion to the original submitter. Also, it will cause inefficient partial completion, because the lower driver can't perform the cloned request anymore and request-based dm needs to requeue and redispatch it to the lower driver again later. That's not good. - So request-based dm needs blk_update_request() to perform the bio completion in the lower driver's completion context, which is more efficient. 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>
This commit is contained in:
parent
e3335de940
commit
32fab448e5
|
@ -1806,6 +1806,22 @@ void end_request(struct request *req, int uptodate)
|
||||||
}
|
}
|
||||||
EXPORT_SYMBOL(end_request);
|
EXPORT_SYMBOL(end_request);
|
||||||
|
|
||||||
|
static int end_that_request_data(struct request *rq, int error,
|
||||||
|
unsigned int nr_bytes, unsigned int bidi_bytes)
|
||||||
|
{
|
||||||
|
if (rq->bio) {
|
||||||
|
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.
|
* blk_end_io - Generic end_io function to complete a request.
|
||||||
* @rq: the request being processed
|
* @rq: the request being processed
|
||||||
|
@ -1832,15 +1848,8 @@ static int blk_end_io(struct request *rq, int error, unsigned int nr_bytes,
|
||||||
struct request_queue *q = rq->q;
|
struct request_queue *q = rq->q;
|
||||||
unsigned long flags = 0UL;
|
unsigned long flags = 0UL;
|
||||||
|
|
||||||
if (rq->bio) {
|
if (end_that_request_data(rq, error, nr_bytes, bidi_bytes))
|
||||||
if (__end_that_request_first(rq, error, nr_bytes))
|
return 1;
|
||||||
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;
|
|
||||||
}
|
|
||||||
|
|
||||||
/* Special feature for tricky drivers */
|
/* Special feature for tricky drivers */
|
||||||
if (drv_callback && drv_callback(rq))
|
if (drv_callback && drv_callback(rq))
|
||||||
|
@ -1922,6 +1931,36 @@ int blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes,
|
||||||
}
|
}
|
||||||
EXPORT_SYMBOL_GPL(blk_end_bidi_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)) {
|
||||||
|
/*
|
||||||
|
* These members are not updated in end_that_request_data()
|
||||||
|
* when all bios are completed.
|
||||||
|
* Update them so that the request stacking driver can find
|
||||||
|
* how many bytes remain in the request later.
|
||||||
|
*/
|
||||||
|
rq->nr_sectors = rq->hard_nr_sectors = 0;
|
||||||
|
rq->current_nr_sectors = rq->hard_cur_sectors = 0;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
EXPORT_SYMBOL_GPL(blk_update_request);
|
||||||
|
|
||||||
/**
|
/**
|
||||||
* blk_end_request_callback - Special helper function for tricky drivers
|
* blk_end_request_callback - Special helper function for tricky drivers
|
||||||
* @rq: the request being processed
|
* @rq: the request being processed
|
||||||
|
|
|
@ -791,6 +791,8 @@ extern void blk_complete_request(struct request *);
|
||||||
extern void __blk_complete_request(struct request *);
|
extern void __blk_complete_request(struct request *);
|
||||||
extern void blk_abort_request(struct request *);
|
extern void blk_abort_request(struct request *);
|
||||||
extern void blk_abort_queue(struct request_queue *);
|
extern void blk_abort_queue(struct request_queue *);
|
||||||
|
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.
|
* blk_end_request() takes bytes instead of sectors as a complete size.
|
||||||
|
|
Loading…
Reference in New Issue