Support bio(REQ_POLLED) polling in the following approach: 1) only support io polling on normal READ/WRITE, and other abnormal IOs still fallback on IRQ mode, so the target io is exactly inside the dm io. 2) hold one refcnt on io->io_count after submitting this dm bio with REQ_POLLED 3) support dm native bio splitting, any dm io instance associated with current bio will be added into one list which head is bio->bi_end_io which will be recovered before ending this bio 4) implement .poll_bio() callback, call bio_poll() on the single target bio inside the dm io which is retrieved via bio->bi_bio_drv_data; call dec_pending() after the target io is done in .poll_bio() 4) enable QUEUE_FLAG_POLL if all underlying queues enable QUEUE_FLAG_POLL, which is based on Jeffle's previous patch. Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- drivers/md/dm-table.c | 24 ++++++++ drivers/md/dm.c | 131 +++++++++++++++++++++++++++++++++++++++++- 2 files changed, 152 insertions(+), 3 deletions(-) diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index ee47a332b462..b14b379442d2 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -1491,6 +1491,12 @@ struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector) return &t->targets[(KEYS_PER_NODE * n) + k]; } +static int device_not_poll_capable(struct dm_target *ti, struct dm_dev *dev, + sector_t start, sector_t len, void *data) +{ + return !blk_queue_poll(bdev_get_queue(dev->bdev)); +} + /* * type->iterate_devices() should be called when the sanity check needs to * iterate and check all underlying data devices. iterate_devices() will @@ -1541,6 +1547,11 @@ static int count_device(struct dm_target *ti, struct dm_dev *dev, return 0; } +static int dm_table_supports_poll(struct dm_table *t) +{ + return !dm_table_any_dev_attr(t, device_not_poll_capable, NULL); +} + /* * Check whether a table has no data devices attached using each * target's iterate_devices method. @@ -2078,6 +2089,19 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q, dm_update_keyslot_manager(q, t); blk_queue_update_readahead(q); + + /* + * Check for request-based device is remained to + * dm_mq_init_request_queue()->blk_mq_init_allocated_queue(). + * For bio-based device, only set QUEUE_FLAG_POLL when all underlying + * devices supporting polling. + */ + if (__table_type_bio_based(t->type)) { + if (dm_table_supports_poll(t)) + blk_queue_flag_set(QUEUE_FLAG_POLL, q); + else + blk_queue_flag_clear(QUEUE_FLAG_POLL, q); + } } unsigned int dm_table_get_num_targets(struct dm_table *t) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 363f12a285ce..cfc2e1915ec4 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -39,6 +39,8 @@ #define DM_COOKIE_ENV_VAR_NAME "DM_COOKIE" #define DM_COOKIE_LENGTH 24 +#define REQ_SAVED_END_IO REQ_DRV + static const char *_name = DM_NAME; static unsigned int major = 0; @@ -72,6 +74,7 @@ struct clone_info { struct dm_io *io; sector_t sector; unsigned sector_count; + bool submit_as_polled; }; /* @@ -99,6 +102,8 @@ struct dm_io { blk_status_t status; atomic_t io_count; struct bio *orig_bio; + void *saved_bio_end_io; + struct hlist_node node; unsigned long start_time; spinlock_t endio_lock; struct dm_stats_aux stats_aux; @@ -687,6 +692,8 @@ static struct dm_target_io *alloc_tio(struct clone_info *ci, struct dm_target *t tio->ti = ti; tio->target_bio_nr = target_bio_nr; + WARN_ON_ONCE(ci->submit_as_polled && !tio->inside_dm_io); + return tio; } @@ -938,8 +945,14 @@ static void dec_pending(struct dm_io *io, blk_status_t error) end_io_acct(io); free_io(md, io); - if (io_error == BLK_STS_DM_REQUEUE) + if (io_error == BLK_STS_DM_REQUEUE) { + /* + * Upper layer won't help us poll split bio, so + * clear REQ_POLLED in case of requeue + */ + bio->bi_opf &= ~REQ_POLLED; return; + } if ((bio->bi_opf & REQ_PREFLUSH) && bio->bi_iter.bi_size) { /* @@ -1366,6 +1379,9 @@ static int clone_bio(struct dm_target_io *tio, struct bio *bio, __bio_clone_fast(clone, bio); + /* REQ_SAVED_END_IO shouldn't be inherited */ + clone->bi_opf &= ~REQ_SAVED_END_IO; + r = bio_crypt_clone(clone, bio, GFP_NOIO); if (r < 0) return r; @@ -1574,6 +1590,46 @@ static bool __process_abnormal_io(struct clone_info *ci, struct dm_target *ti, return true; } +/* + * Reuse ->bi_end_io as hlist head for storing all dm_io instances + * associated with this bio, and this bio's bi_end_io has to be + * stored in one of 'dm_io' instance first. + */ +static inline struct hlist_head *dm_get_bio_hlist_head(struct bio *bio) +{ + WARN_ON_ONCE(!(bio->bi_opf & REQ_SAVED_END_IO)); + return (struct hlist_head *)&bio->bi_end_io; +} + +static void dm_setup_polled_io(struct clone_info *ci) +{ + struct bio *bio = ci->bio; + + /* + * Only support bio polling for normal IO, and the target io is + * exactly inside the dm io instance + */ + ci->submit_as_polled = bio->bi_opf & REQ_POLLED; + if (!ci->submit_as_polled) + return; + + INIT_HLIST_NODE(&ci->io->node); + /* + * Save .bi_end_io into dm_io, so that we can reuse .bi_end_io + * for storing dm_io list + */ + if (bio->bi_opf & REQ_SAVED_END_IO) { + ci->io->saved_bio_end_io = NULL; + } else { + ci->io->saved_bio_end_io = bio->bi_end_io; + bio->bi_opf |= REQ_SAVED_END_IO; + INIT_HLIST_HEAD(dm_get_bio_hlist_head(bio)); + + /* tell block layer to poll me */ + bio->bi_cookie = ~BLK_QC_T_NONE; + } +} + /* * Select the correct strategy for processing a non-flush bio. */ @@ -1590,6 +1646,8 @@ static int __split_and_process_non_flush(struct clone_info *ci) if (__process_abnormal_io(ci, ti, &r)) return r; + dm_setup_polled_io(ci); + len = min_t(sector_t, max_io_len(ti, ci->sector), ci->sector_count); r = __clone_and_map_data_bio(ci, ti, ci->sector, &len); @@ -1608,6 +1666,7 @@ static void init_clone_info(struct clone_info *ci, struct mapped_device *md, ci->map = map; ci->io = alloc_io(md, bio); ci->sector = bio->bi_iter.bi_sector; + ci->submit_as_polled = false; } #define __dm_part_stat_sub(part, field, subnd) \ @@ -1666,8 +1725,17 @@ static void __split_and_process_bio(struct mapped_device *md, } } - /* drop the extra reference count */ - dec_pending(ci.io, errno_to_blk_status(error)); + /* + * Drop the extra reference count for non-POLLED bio, and hold one + * reference for POLLED bio, which will be released in dm_poll_bio + * + * Add every dm_io instance into the hlist_head which is stored in + * bio->bi_end_io, so that dm_poll_bio can poll them all. + */ + if (!ci.submit_as_polled) + dec_pending(ci.io, errno_to_blk_status(error)); + else + hlist_add_head(&ci.io->node, dm_get_bio_hlist_head(bio)); } static void dm_submit_bio(struct bio *bio) @@ -1707,6 +1775,62 @@ static void dm_submit_bio(struct bio *bio) dm_put_live_table(md, srcu_idx); } +static bool dm_poll_dm_io(struct dm_io *io, unsigned int flags) +{ + WARN_ON_ONCE(!io->tio.inside_dm_io); + + bio_poll(&io->tio.clone, flags); + + /* bio_poll holds the last reference */ + return atomic_read(&io->io_count) == 1; +} + +static int dm_poll_bio(struct bio *bio, unsigned int flags) +{ + struct dm_io *io; + void *saved_bi_end_io = NULL; + struct hlist_head tmp = HLIST_HEAD_INIT; + struct hlist_head *head = dm_get_bio_hlist_head(bio); + struct hlist_node *next; + + /* We only poll normal bio which was marked as REQ_SAVED_END_IO */ + if (!(bio->bi_opf & REQ_SAVED_END_IO)) + return 0; + + WARN_ON_ONCE(hlist_empty(head)); + + hlist_move_list(head, &tmp); + + hlist_for_each_entry(io, &tmp, node) { + if (io->saved_bio_end_io) { + saved_bi_end_io = io->saved_bio_end_io; + break; + } + } + + /* restore .bi_end_io before completing dm io */ + WARN_ON_ONCE(!saved_bi_end_io); + bio->bi_opf &= ~REQ_SAVED_END_IO; + bio->bi_end_io = saved_bi_end_io; + + hlist_for_each_entry_safe(io, next, &tmp, node) { + if (dm_poll_dm_io(io, flags)) { + hlist_del_init(&io->node); + dec_pending(io, 0); + } + } + + /* Not done, make sure at least one dm_io stores the .bi_end_io*/ + if (!hlist_empty(&tmp)) { + io = hlist_entry(tmp.first, struct dm_io, node); + io->saved_bio_end_io = saved_bi_end_io; + bio->bi_opf |= REQ_SAVED_END_IO; + hlist_move_list(&tmp, head); + return 0; + } + return 1; +} + /*----------------------------------------------------------------- * An IDR is used to keep track of allocated minor numbers. *---------------------------------------------------------------*/ @@ -3121,6 +3245,7 @@ static const struct pr_ops dm_pr_ops = { static const struct block_device_operations dm_blk_dops = { .submit_bio = dm_submit_bio, + .poll_bio = dm_poll_bio, .open = dm_blk_open, .release = dm_blk_close, .ioctl = dm_blk_ioctl, -- 2.31.1 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel