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Commit 893a1c97 authored by Jens Axboe's avatar Jens Axboe
Browse files

blk-mq: allow REQ_NOWAIT to return an error inline 



By default, if a caller sets REQ_NOWAIT and we need to block, we'll
return -EAGAIN through the bio->bi_end_io() callback. For some use
cases, this makes it hard to use.

Allow a caller to ask for inline return of errors related to
blocking by also setting REQ_NOWAIT_INLINE.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c0e48f9d

block/blk-mq.c

+6 −2
Original line number Diff line number Diff line
@@ -1960,9 +1960,13 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) 
	rq = blk_mq_get_request(q, bio, &data);

	if (unlikely(!rq)) {

		rq_qos_cleanup(q, bio);

		if (bio->bi_opf & REQ_NOWAIT)



		cookie = BLK_QC_T_NONE;

		if (bio->bi_opf & REQ_NOWAIT_INLINE)

			cookie = BLK_QC_T_EAGAIN;

		else if (bio->bi_opf & REQ_NOWAIT)

			bio_wouldblock_error(bio);

		return BLK_QC_T_NONE;

		return cookie;

	}



	trace_block_getrq(q, bio, bio->bi_opf);

include/linux/blk_types.h

+4 −1
Original line number Diff line number Diff line
@@ -311,6 +311,7 @@ enum req_flag_bits { 
	__REQ_RAHEAD,		/* read ahead, can fail anytime */

	__REQ_BACKGROUND,	/* background IO */

	__REQ_NOWAIT,           /* Don't wait if request will block */

	__REQ_NOWAIT_INLINE,	/* Return would-block error inline */

	/*

	 * When a shared kthread needs to issue a bio for a cgroup, doing

	 * so synchronously can lead to priority inversions as the kthread
@@ -345,6 +346,7 @@ enum req_flag_bits { 
#define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)

#define REQ_BACKGROUND		(1ULL << __REQ_BACKGROUND)

#define REQ_NOWAIT		(1ULL << __REQ_NOWAIT)

#define REQ_NOWAIT_INLINE	(1ULL << __REQ_NOWAIT_INLINE)

#define REQ_CGROUP_PUNT		(1ULL << __REQ_CGROUP_PUNT)



#define REQ_NOUNMAP		(1ULL << __REQ_NOUNMAP)
@@ -418,12 +420,13 @@ static inline int op_stat_group(unsigned int op) 


typedef unsigned int blk_qc_t;

#define BLK_QC_T_NONE		-1U

#define BLK_QC_T_EAGAIN		-2U

#define BLK_QC_T_SHIFT		16

#define BLK_QC_T_INTERNAL	(1U << 31)



static inline bool blk_qc_t_valid(blk_qc_t cookie)

{

	return cookie != BLK_QC_T_NONE;

	return cookie != BLK_QC_T_NONE && cookie != BLK_QC_T_EAGAIN;

}



static inline unsigned int blk_qc_t_to_queue_num(blk_qc_t cookie)