From 0f14d60a023cc4fe68758e0fcdc0ce82a82dde7d Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 12 Apr 2022 16:56:15 +0800 Subject: dm: improve dm_io reference counting Currently each dm_io's reference counter is grabbed before calling __map_bio(), this way isn't efficient since we can move this grabbing to initialization time inside alloc_io(). Meantime it becomes typical async io reference counter model: one is for submission side, the other is for completion side, and the io won't be completed until both sides are done. Signed-off-by: Ming Lei Signed-off-by: Mike Snitzer --- drivers/md/dm.c | 53 +++++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 39 insertions(+), 14 deletions(-) (limited to 'drivers/md/dm.c') diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 7cae8235fbe1..6bc2dc8071fc 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -590,7 +590,9 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio) io = container_of(tio, struct dm_io, tio); io->magic = DM_IO_MAGIC; io->status = BLK_STS_OK; - atomic_set(&io->io_count, 1); + + /* one ref is for submission, the other is for completion */ + atomic_set(&io->io_count, 2); this_cpu_inc(*md->pending_io); io->orig_bio = bio; io->md = md; @@ -955,11 +957,6 @@ static void dm_io_complete(struct dm_io *io) } } -static void dm_io_inc_pending(struct dm_io *io) -{ - atomic_inc(&io->io_count); -} - /* * Decrements the number of outstanding ios that a bio has been * cloned into, completing the original io if necc. @@ -1316,7 +1313,6 @@ static void __map_bio(struct bio *clone) /* * Map the clone. */ - dm_io_inc_pending(io); tio->old_sector = clone->bi_iter.bi_sector; if (static_branch_unlikely(&swap_bios_enabled) && @@ -1426,11 +1422,12 @@ static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci, } } -static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti, +static int __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti, unsigned num_bios, unsigned *len) { struct bio_list blist = BIO_EMPTY_LIST; struct bio *clone; + int ret = 0; switch (num_bios) { case 0: @@ -1440,6 +1437,7 @@ static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti, setup_split_accounting(ci, *len); clone = alloc_tio(ci, ti, 0, len, GFP_NOIO); __map_bio(clone); + ret = 1; break; default: /* dm_accept_partial_bio() is not supported with shared tio->len_ptr */ @@ -1447,9 +1445,12 @@ static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti, while ((clone = bio_list_pop(&blist))) { dm_tio_set_flag(clone_to_tio(clone), DM_TIO_IS_DUPLICATE_BIO); __map_bio(clone); + ret += 1; } break; } + + return ret; } static void __send_empty_flush(struct clone_info *ci) @@ -1470,8 +1471,19 @@ static void __send_empty_flush(struct clone_info *ci) ci->sector_count = 0; ci->io->tio.clone.bi_iter.bi_size = 0; - while ((ti = dm_table_get_target(ci->map, target_nr++))) - __send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL); + while ((ti = dm_table_get_target(ci->map, target_nr++))) { + int bios; + + atomic_add(ti->num_flush_bios, &ci->io->io_count); + bios = __send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL); + atomic_sub(ti->num_flush_bios - bios, &ci->io->io_count); + } + + /* + * alloc_io() takes one extra reference for submission, so the + * reference won't reach 0 without the following subtraction + */ + atomic_sub(1, &ci->io->io_count); bio_uninit(ci->bio); } @@ -1480,11 +1492,18 @@ static void __send_changing_extent_only(struct clone_info *ci, struct dm_target unsigned num_bios) { unsigned len; + int bios; len = min_t(sector_t, ci->sector_count, max_io_len_target_boundary(ti, dm_target_offset(ti, ci->sector))); - __send_duplicate_bios(ci, ti, num_bios, &len); + atomic_add(num_bios, &ci->io->io_count); + bios = __send_duplicate_bios(ci, ti, num_bios, &len); + /* + * alloc_io() takes one extra reference for submission, so the + * reference won't reach 0 without the following (+1) subtraction + */ + atomic_sub(num_bios - bios + 1, &ci->io->io_count); ci->sector += len; ci->sector_count -= len; @@ -1669,9 +1688,15 @@ out: * Add every dm_io instance into the hlist_head which is stored in * bio->bi_private, so that dm_poll_bio can poll them all. */ - if (error || !ci.submit_as_polled) - dm_io_dec_pending(ci.io, error); - else + if (error || !ci.submit_as_polled) { + /* + * In case of submission failure, the extra reference for + * submitting io isn't consumed yet + */ + if (error) + atomic_dec(&io->io_count); + dm_io_dec_pending(io, error); + } else dm_queue_poll_io(bio, io); } -- cgit v1.2.3