From 23ca2bb6c6104db9d4cff4e33cbabee303c49d4d Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Wed, 15 Oct 2014 14:46:58 +0100 Subject: [PATCH] dm thin: direct dispatch when breaking sharing This use of direct submission in process_shared_bio() reduces latency for submitting bios in the shared cell by avoiding adding those bios to the deferred list and waiting for the next iteration of the worker. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer --- drivers/md/dm-thin.c | 70 ++++++++++++++++++++++++++++++++++++-------- 1 file changed, 57 insertions(+), 13 deletions(-) diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 5036d4b3f368..3f3a66124d46 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -1390,11 +1390,53 @@ static void break_sharing(struct thin_c *tc, struct bio *bio, dm_block_t block, } } +static void __remap_and_issue_shared_cell(void *context, + struct dm_bio_prison_cell *cell) +{ + struct remap_info *info = context; + struct bio *bio; + + while ((bio = bio_list_pop(&cell->bios))) { + if ((bio_data_dir(bio) == WRITE) || + (bio->bi_rw & (REQ_DISCARD | REQ_FLUSH | REQ_FUA))) + bio_list_add(&info->defer_bios, bio); + else { + struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));; + + h->shared_read_entry = dm_deferred_entry_inc(info->tc->pool->shared_read_ds); + inc_all_io_entry(info->tc->pool, bio); + bio_list_add(&info->issue_bios, bio); + } + } +} + +static void remap_and_issue_shared_cell(struct thin_c *tc, + struct dm_bio_prison_cell *cell, + dm_block_t block) +{ + struct bio *bio; + struct remap_info info; + + info.tc = tc; + bio_list_init(&info.defer_bios); + bio_list_init(&info.issue_bios); + + cell_visit_release(tc->pool, __remap_and_issue_shared_cell, + &info, cell); + + while ((bio = bio_list_pop(&info.defer_bios))) + thin_defer_bio(tc, bio); + + while ((bio = bio_list_pop(&info.issue_bios))) + remap_and_issue(tc, bio, block); +} + static void process_shared_bio(struct thin_c *tc, struct bio *bio, dm_block_t block, - struct dm_thin_lookup_result *lookup_result) + struct dm_thin_lookup_result *lookup_result, + struct dm_bio_prison_cell *virt_cell) { - struct dm_bio_prison_cell *cell; + struct dm_bio_prison_cell *data_cell; struct pool *pool = tc->pool; struct dm_cell_key key; @@ -1403,19 +1445,23 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio, * of being broken so we have nothing further to do here. */ build_data_key(tc->td, lookup_result->block, &key); - if (bio_detain(pool, &key, bio, &cell)) + if (bio_detain(pool, &key, bio, &data_cell)) { + cell_defer_no_holder(tc, virt_cell); return; + } - if (bio_data_dir(bio) == WRITE && bio->bi_iter.bi_size) - break_sharing(tc, bio, block, &key, lookup_result, cell); - else { + if (bio_data_dir(bio) == WRITE && bio->bi_iter.bi_size) { + break_sharing(tc, bio, block, &key, lookup_result, data_cell); + cell_defer_no_holder(tc, virt_cell); + } else { struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook)); h->shared_read_entry = dm_deferred_entry_inc(pool->shared_read_ds); inc_all_io_entry(pool, bio); - cell_defer_no_holder(tc, cell); - remap_and_issue(tc, bio, lookup_result->block); + + remap_and_issue_shared_cell(tc, data_cell, lookup_result->block); + remap_and_issue_shared_cell(tc, virt_cell, lookup_result->block); } } @@ -1484,11 +1530,9 @@ static void process_cell(struct thin_c *tc, struct dm_bio_prison_cell *cell) r = dm_thin_find_block(tc->td, block, 1, &lookup_result); switch (r) { case 0: - if (lookup_result.shared) { - process_shared_bio(tc, bio, block, &lookup_result); - // FIXME: we can't remap because we're waiting on a commit - cell_defer_no_holder(tc, cell); /* FIXME: pass this cell into process_shared? */ - } else { + if (lookup_result.shared) + process_shared_bio(tc, bio, block, &lookup_result, cell); + else { inc_all_io_entry(pool, bio); remap_and_issue(tc, bio, lookup_result.block); inc_remap_and_issue_cell(tc, cell, lookup_result.block); -- 2.34.1