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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: Jens Axboe <axboe@kernel.dk>
alistair/sunxi64-5.4-dsi
Jens Axboe 2019-07-16 13:55:23 -06:00
parent c0e48f9dea
commit 893a1c9720
2 changed files with 10 additions and 3 deletions
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8
block/blk-mq.c
View File

@ -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);

5
include/linux/blk_types.h
View File

@ -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)