From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
A new flag BIO_NOWAIT is introduced to identify bio's
orignating from iocb with IOCB_NOWAIT. This flag indicates
to return immediately if a request cannot be made instead
of retrying.
To facilitate this, QUEUE_FLAG_NOWAIT is set to devices
which support this. While currently this is set to
virtio and sd only. Support to more devices will be added soon.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
---
block/blk-core.c | 24 ++++++++++++++++++++++--
block/blk-mq-sched.c | 3 +++
block/blk-mq.c | 4 ++++
drivers/block/virtio_blk.c | 3 +++
drivers/scsi/sd.c | 3 +++
fs/direct-io.c | 11 +++++++++--
include/linux/bio.h | 6 ++++++
include/linux/blk_types.h | 1 +
include/linux/blkdev.h | 2 ++
9 files changed, 53 insertions(+), 4 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index d772c22..95a9b18 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1232,6 +1232,11 @@ static struct request *get_request(struct request_queue *q, unsigned int op,
if (!IS_ERR(rq))
return rq;
+ if (bio && bio_flagged(bio, BIO_NOWAIT)) {
+ blk_put_rl(rl);
+ return ERR_PTR(-EAGAIN);
+ }
+
if (!gfpflags_allow_blocking(gfp_mask) || unlikely(blk_queue_dying(q))) {
blk_put_rl(rl);
return rq;
@@ -1870,6 +1875,18 @@ generic_make_request_checks(struct bio *bio)
goto end_io;
}
+ if (bio_flagged(bio, BIO_NOWAIT)) {
+ if (!blk_queue_nowait(q)) {
+ err = -EOPNOTSUPP;
+ goto end_io;
+ }
+ if (!(bio->bi_opf & (REQ_SYNC | REQ_IDLE))) {
+ err = -EINVAL;
+ goto end_io;
+ }
+ }
+
+
part = bio->bi_bdev->bd_part;
if (should_fail_request(part, bio->bi_iter.bi_size) ||
should_fail_request(&part_to_disk(part)->part0,
@@ -2021,7 +2038,7 @@ blk_qc_t generic_make_request(struct bio *bio)
do {
struct request_queue *q = bdev_get_queue(bio->bi_bdev);
- if (likely(blk_queue_enter(q, false) == 0)) {
+ if (likely(blk_queue_enter(q, bio_flagged(bio, BIO_NOWAIT)) == 0)) {
struct bio_list lower, same;
/* Create a fresh bio_list for all subordinate requests */
@@ -2046,7 +2063,10 @@ blk_qc_t generic_make_request(struct bio *bio)
bio_list_merge(&bio_list_on_stack[0], &same);
bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
} else {
- bio_io_error(bio);
+ if (unlikely(!blk_queue_dying(q) && bio_flagged(bio, BIO_NOWAIT)))
+ bio_wouldblock_error(bio);
+ else
+ bio_io_error(bio);
}
bio = bio_list_pop(&bio_list_on_stack[0]);
} while (bio);
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 09af8ff..40e78b5 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -119,6 +119,9 @@ struct request *blk_mq_sched_get_request(struct request_queue *q,
if (likely(!data->hctx))
data->hctx = blk_mq_map_queue(q, data->ctx->cpu);
+ if (likely(bio) && bio_flagged(bio, BIO_NOWAIT))
+ data->flags |= BLK_MQ_REQ_NOWAIT;
+
if (e) {
data->flags |= BLK_MQ_REQ_INTERNAL;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6b6e7bc..2d90b12 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1511,6 +1511,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
rq = blk_mq_sched_get_request(q, bio, bio->bi_opf, &data);
if (unlikely(!rq)) {
__wbt_done(q->rq_wb, wb_acct);
+ if (bio && bio_flagged(bio, BIO_NOWAIT))
+ bio_wouldblock_error(bio);
return BLK_QC_T_NONE;
}
@@ -1635,6 +1637,8 @@ static blk_qc_t blk_sq_make_request(struct request_queue *q, struct bio *bio)
rq = blk_mq_sched_get_request(q, bio, bio->bi_opf, &data);
if (unlikely(!rq)) {
__wbt_done(q->rq_wb, wb_acct);
+ if (bio && bio_flagged(bio, BIO_NOWAIT))
+ bio_wouldblock_error(bio);
return BLK_QC_T_NONE;
}
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 1d4c9f8..7481124 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -731,6 +731,9 @@ static int virtblk_probe(struct virtio_device *vdev)
/* No real sector limit. */
blk_queue_max_hw_sectors(q, -1U);
+ /* Request queue supports BIO_NOWAIT */
+ queue_flag_set_unlocked(QUEUE_FLAG_NOWAIT, q);
+
/* Host can optionally specify maximum segment size and number of
* segments. */
err = virtio_cread_feature(vdev, VIRTIO_BLK_F_SIZE_MAX,
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index fcfeddc..9df85ee 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3177,6 +3177,9 @@ static int sd_probe(struct device *dev)
SD_MOD_TIMEOUT);
}
+ /* Support BIO_NOWAIT */
+ queue_flag_set_unlocked(QUEUE_FLAG_NOWAIT, sdp->request_queue);
+
device_initialize(&sdkp->dev);
sdkp->dev.parent = dev;
sdkp->dev.class = &sd_disk_class;
diff --git a/fs/direct-io.c b/fs/direct-io.c
index a04ebea..f6835d3 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -386,6 +386,9 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
else
bio->bi_end_io = dio_bio_end_io;
+ if (dio->iocb->ki_flags & IOCB_NOWAIT)
+ bio_set_flag(bio, BIO_NOWAIT);
+
sdio->bio = bio;
sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
}
@@ -480,8 +483,12 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio)
unsigned i;
int err;
- if (bio->bi_error)
- dio->io_error = -EIO;
+ if (bio->bi_error) {
+ if (bio_flagged(bio, BIO_NOWAIT))
+ dio->io_error = -EAGAIN;
+ else
+ dio->io_error = -EIO;
+ }
if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty) {
err = bio->bi_error;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 8e52119..1a92707 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -425,6 +425,12 @@ static inline void bio_io_error(struct bio *bio)
bio_endio(bio);
}
+static inline void bio_wouldblock_error(struct bio *bio)
+{
+ bio->bi_error = -EAGAIN;
+ bio_endio(bio);
+}
+
struct request_queue;
extern int bio_phys_segments(struct request_queue *, struct bio *);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d703acb..514c08e 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -102,6 +102,7 @@ struct bio {
#define BIO_REFFED 8 /* bio has elevated ->bi_cnt */
#define BIO_THROTTLED 9 /* This bio has already been subjected to
* throttling rules. Don't do it again. */
+#define BIO_NOWAIT 10 /* don't block over blk device congestion */
/*
* Flags starting here get preserved by bio_reset() - this includes
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 5a7da60..ae38ab6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -611,6 +611,7 @@ struct request_queue {
#define QUEUE_FLAG_DAX 26 /* device supports DAX */
#define QUEUE_FLAG_STATS 27 /* track rq completion times */
#define QUEUE_FLAG_RESTART 28 /* queue needs restart at completion */
+#define QUEUE_FLAG_NOWAIT 29 /* queue supports BIO_NOWAIT */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -701,6 +702,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
#define blk_queue_secure_erase(q) \
(test_bit(QUEUE_FLAG_SECERASE, &(q)->queue_flags))
#define blk_queue_dax(q) test_bit(QUEUE_FLAG_DAX, &(q)->queue_flags)
+#define blk_queue_nowait(q) test_bit(QUEUE_FLAG_NOWAIT, &(q)->queue_flags)
#define blk_noretry_request(rq) \
((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \
--
2.10.2
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