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dm: optimize bio-based NVMe IO submission
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Upper level bio-based drivers that stack immediately ontop of NVMe can
leverage direct_make_request().  In addition DM's NVMe bio-based
will initially only ever have one NVMe device that it submits IO to at a
time.  There is no splitting needed.  Enhance DM core so that
DM_TYPE_NVME_BIO_BASED's IO submission takes advantage of both of these
characteristics.

Signed-off-by: Mike Snitzer <[email protected]>
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@snitm
snitm committed Dec 20, 2017
1 parent 22c1185 commit 978e51b
Showing 1 changed file with 120 additions and 34 deletions.
154 changes: 120 additions & 34 deletions drivers/md/dm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -532,7 +532,9 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
return r;
}

static struct dm_io *alloc_io(struct mapped_device *md)
static void start_io_acct(struct dm_io *io);

static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
{
struct dm_io *io;
struct dm_target_io *tio;
Expand All @@ -548,6 +550,13 @@ static struct dm_io *alloc_io(struct mapped_device *md)

io = container_of(tio, struct dm_io, tio);
io->magic = DM_IO_MAGIC;
io->status = 0;
atomic_set(&io->io_count, 1);
io->orig_bio = bio;
io->md = md;
spin_lock_init(&io->endio_lock);

start_io_acct(io);

return io;
}
Expand Down Expand Up @@ -924,7 +933,7 @@ static void clone_endio(struct bio *bio)
struct mapped_device *md = tio->io->md;
dm_endio_fn endio = tio->ti->type->end_io;

if (unlikely(error == BLK_STS_TARGET)) {
if (unlikely(error == BLK_STS_TARGET) && md->type != DM_TYPE_NVME_BIO_BASED) {
if (bio_op(bio) == REQ_OP_WRITE_SAME &&
!bio->bi_disk->queue->limits.max_write_same_sectors)
disable_write_same(md);
Expand Down Expand Up @@ -1191,13 +1200,15 @@ void dm_remap_zone_report(struct dm_target *ti, struct bio *bio, sector_t start)
}
EXPORT_SYMBOL_GPL(dm_remap_zone_report);

static void __map_bio(struct dm_target_io *tio)
static blk_qc_t __map_bio(struct dm_target_io *tio)
{
int r;
sector_t sector;
struct bio *clone = &tio->clone;
struct dm_io *io = tio->io;
struct mapped_device *md = io->md;
struct dm_target *ti = tio->ti;
blk_qc_t ret = BLK_QC_T_NONE;

clone->bi_end_io = clone_endio;

Expand All @@ -1217,7 +1228,10 @@ static void __map_bio(struct dm_target_io *tio)
/* the bio has been remapped so dispatch it */
trace_block_bio_remap(clone->bi_disk->queue, clone,
bio_dev(io->orig_bio), sector);
generic_make_request(clone);
if (md->type == DM_TYPE_NVME_BIO_BASED)
ret = direct_make_request(clone);
else
ret = generic_make_request(clone);
break;
case DM_MAPIO_KILL:
free_tio(tio);
Expand All @@ -1231,6 +1245,8 @@ static void __map_bio(struct dm_target_io *tio)
DMWARN("unimplemented target map return value: %d", r);
BUG();
}

return ret;
}

static void bio_setup_sector(struct bio *bio, sector_t sector, unsigned len)
Expand Down Expand Up @@ -1315,8 +1331,8 @@ static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
}
}

static void __clone_and_map_simple_bio(struct clone_info *ci,
struct dm_target_io *tio, unsigned *len)
static blk_qc_t __clone_and_map_simple_bio(struct clone_info *ci,
struct dm_target_io *tio, unsigned *len)
{
struct bio *clone = &tio->clone;

Expand All @@ -1326,7 +1342,7 @@ static void __clone_and_map_simple_bio(struct clone_info *ci,
if (len)
bio_setup_sector(clone, ci->sector, *len);

__map_bio(tio);
return __map_bio(tio);
}

static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
Expand All @@ -1340,7 +1356,7 @@ static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,

while ((bio = bio_list_pop(&blist))) {
tio = container_of(bio, struct dm_target_io, clone);
__clone_and_map_simple_bio(ci, tio, len);
(void) __clone_and_map_simple_bio(ci, tio, len);
}
}

Expand Down Expand Up @@ -1370,7 +1386,7 @@ static int __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti,
free_tio(tio);
return r;
}
__map_bio(tio);
(void) __map_bio(tio);

return 0;
}
Expand Down Expand Up @@ -1482,30 +1498,30 @@ static int __split_and_process_non_flush(struct clone_info *ci)
return 0;
}

static void init_clone_info(struct clone_info *ci, struct mapped_device *md,
struct dm_table *map, struct bio *bio)
{
ci->map = map;
ci->io = alloc_io(md, bio);
ci->sector = bio->bi_iter.bi_sector;
}

/*
* Entry point to split a bio into clones and submit them to the targets.
*/
static void __split_and_process_bio(struct mapped_device *md,
struct dm_table *map, struct bio *bio)
static blk_qc_t __split_and_process_bio(struct mapped_device *md,
struct dm_table *map, struct bio *bio)
{
struct clone_info ci;
blk_qc_t ret = BLK_QC_T_NONE;
int error = 0;

if (unlikely(!map)) {
bio_io_error(bio);
return;
return ret;
}

ci.map = map;
ci.io = alloc_io(md);
ci.io->status = 0;
atomic_set(&ci.io->io_count, 1);
ci.io->orig_bio = bio;
ci.io->md = md;
spin_lock_init(&ci.io->endio_lock);
ci.sector = bio->bi_iter.bi_sector;

start_io_acct(ci.io);
init_clone_info(&ci, md, map, bio);

if (bio->bi_opf & REQ_PREFLUSH) {
ci.bio = &ci.io->md->flush_bio;
Expand Down Expand Up @@ -1538,23 +1554,71 @@ static void __split_and_process_bio(struct mapped_device *md,
ci.io->orig_bio = b;
bio_advance(bio, (bio_sectors(bio) - ci.sector_count) << 9);
bio_chain(b, bio);
generic_make_request(bio);
ret = generic_make_request(bio);
break;
}
}
}

/* drop the extra reference count */
dec_pending(ci.io, errno_to_blk_status(error));
return ret;
}

/*
* The request function that remaps the bio to one target and
* splits off any remainder.
* Optimized variant of __split_and_process_bio that leverages the
* fact that targets that use it do _not_ have a need to split bios.
*/
static blk_qc_t dm_make_request(struct request_queue *q, struct bio *bio)
static blk_qc_t __process_bio(struct mapped_device *md,
struct dm_table *map, struct bio *bio)
{
struct clone_info ci;
blk_qc_t ret = BLK_QC_T_NONE;
int error = 0;

if (unlikely(!map)) {
bio_io_error(bio);
return ret;
}

init_clone_info(&ci, md, map, bio);

if (bio->bi_opf & REQ_PREFLUSH) {
ci.bio = &ci.io->md->flush_bio;
ci.sector_count = 0;
error = __send_empty_flush(&ci);
/* dec_pending submits any data associated with flush */
} else {
struct dm_target *ti = md->immutable_target;
struct dm_target_io *tio;

/*
* Defend against IO still getting in during teardown
* - as was seen for a time with nvme-fcloop
*/
if (unlikely(WARN_ON_ONCE(!ti || !dm_target_is_valid(ti)))) {
error = -EIO;
goto out;
}

tio = alloc_tio(&ci, ti, 0, GFP_NOIO);
ci.bio = bio;
ci.sector_count = bio_sectors(bio);
ret = __clone_and_map_simple_bio(&ci, tio, NULL);
}
out:
/* drop the extra reference count */
dec_pending(ci.io, errno_to_blk_status(error));
return ret;
}

typedef blk_qc_t (process_bio_fn)(struct mapped_device *, struct dm_table *, struct bio *);

static blk_qc_t __dm_make_request(struct request_queue *q, struct bio *bio,
process_bio_fn process_bio)
{
struct mapped_device *md = q->queuedata;
blk_qc_t ret = BLK_QC_T_NONE;
int srcu_idx;
struct dm_table *map;

Expand All @@ -1568,12 +1632,27 @@ static blk_qc_t dm_make_request(struct request_queue *q, struct bio *bio)
queue_io(md, bio);
else
bio_io_error(bio);
return BLK_QC_T_NONE;
return ret;
}

__split_and_process_bio(md, map, bio);
ret = process_bio(md, map, bio);

dm_put_live_table(md, srcu_idx);
return BLK_QC_T_NONE;
return ret;
}

/*
* The request function that remaps the bio to one target and
* splits off any remainder.
*/
static blk_qc_t dm_make_request(struct request_queue *q, struct bio *bio)
{
return __dm_make_request(q, bio, __split_and_process_bio);
}

static blk_qc_t dm_make_request_nvme(struct request_queue *q, struct bio *bio)
{
return __dm_make_request(q, bio, __process_bio);
}

static int dm_any_congested(void *congested_data, int bdi_bits)
Expand Down Expand Up @@ -1927,6 +2006,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
{
struct dm_table *old_map;
struct request_queue *q = md->queue;
bool request_based = dm_table_request_based(t);
sector_t size;

lockdep_assert_held(&md->suspend_lock);
Expand All @@ -1950,12 +2030,15 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
* This must be done before setting the queue restrictions,
* because request-based dm may be run just after the setting.
*/
if (dm_table_request_based(t)) {
if (request_based)
dm_stop_queue(q);

if (request_based || md->type == DM_TYPE_NVME_BIO_BASED) {
/*
* Leverage the fact that request-based DM targets are
* immutable singletons and establish md->immutable_target
* - used to optimize both dm_request_fn and dm_mq_queue_rq
* Leverage the fact that request-based DM targets and
* NVMe bio based targets are immutable singletons
* - used to optimize both dm_request_fn and dm_mq_queue_rq;
* and __process_bio.
*/
md->immutable_target = dm_table_get_immutable_target(t);
}
Expand Down Expand Up @@ -2073,10 +2156,13 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
break;
case DM_TYPE_BIO_BASED:
case DM_TYPE_DAX_BIO_BASED:
case DM_TYPE_NVME_BIO_BASED:
dm_init_normal_md_queue(md);
blk_queue_make_request(md->queue, dm_make_request);
break;
case DM_TYPE_NVME_BIO_BASED:
dm_init_normal_md_queue(md);
blk_queue_make_request(md->queue, dm_make_request_nvme);
break;
case DM_TYPE_NONE:
WARN_ON_ONCE(true);
break;
Expand Down

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