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block: Update blk_update_request() documentation

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Although the original intent was to use blk_update_request() in stacking
block drivers only, it is used much more widely today. Reflect this in the
documentation block above this function. See also:
* commit 32fab448e5 ("block: add request update interface").
* commit 2e60e02297 ("block: clean up request completion API").
* commit ed6565e734 ("block: handle partial completions for special
  payload requests").

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210519175226.8853-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2021-05-19 10:52:26 -07:00 committed by Jens Axboe
parent 613471549f
commit 7cc2623d1c
1 changed files with 4 additions and 8 deletions
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12
block/blk-core.c
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@ -1384,26 +1384,22 @@ void blk_steal_bios(struct bio_list *list, struct request *rq)
EXPORT_SYMBOL_GPL(blk_steal_bios);
/**
* blk_update_request - Special helper function for request stacking drivers
* blk_update_request - Complete multiple bytes without completing the request
* @req: the request being processed
* @error: block status code
* @nr_bytes: number of bytes to complete @req
* @nr_bytes: number of bytes to complete for @req
*
* Description:
* Ends I/O on a number of bytes attached to @req, but doesn't complete
* the request structure even if @req doesn't have leftover.
* If @req 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_mq_end_request instead.
*
* Passing the result of blk_rq_bytes() as @nr_bytes guarantees
* %false return from this function.
*
* Note:
* The RQF_SPECIAL_PAYLOAD flag is ignored on purpose in both
* blk_rq_bytes() and in blk_update_request().
* The RQF_SPECIAL_PAYLOAD flag is ignored on purpose in this function
* except in the consistency check at the end of this function.
*
* Return:
* %false - this request doesn't have any more data