From: Mike Snitzer snitzer@redhat.com

Discontinue issuing writethrough write IO in series to the origin and then cache.

Use bio_clone_fast() to create a new origin clone bio that will be mapped to the origin device and then bio_chain() it to the bio that gets remapped to the cache device. The origin clone bio does _not_ have a copy of the per_bio_data -- as such check_if_tick_bio_needed() will not be called.

The cache bio (parent bio) will not complete until the origin bio has completed -- this fulfills bio_clone_fast()'s requirements as well as the requirement to not complete the original IO until the write IO has completed to both the origin and cache device.

Signed-off-by: Mike Snitzer snitzer@redhat.com

(cherry picked from commit 2df3bae9a6543e90042291707b8db0cbfbae9ee9)

Fixes: 4ec34f2196d125ff781170ddc6c3058c08ec5e73 (dm bio record: save/restore bi_end_io and bi_integrity )

4ec34f21 introduced a mkfs.ext4 hang on a LVM device that has been modified with lvconvert --cachemode=writethrough.

CC:stable@vger.kernel.org for 4.14.y

Signed-off-by: John Donnelly john.p.donnelly@oracle.com Reviewed-by: Somasundaram Krishnasamy somasundaram.krishnasamy@oracle.com

conflicts: drivers/md/dm-cache-target.c. - Corrected usage of writethrough_mode(&cache->feature) that was caught by compiler, and removed unused static functions : writethrough_endio(), defer_writethrough_bio(), wake_deferred_writethrough_worker() that generated warnings. --- drivers/md/dm-cache-target.c | 92 ++++++++++++++++++-------------------------- 1 file changed, 37 insertions(+), 55 deletions(-)

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 69cdb29ef6be..2732d1df05fa 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -450,6 +450,7 @@ struct cache { struct work_struct migration_worker; struct delayed_work waker; struct dm_bio_prison_v2 *prison; + struct bio_set *bs; mempool_t *migration_pool; @@ -537,11 +538,6 @@ static void wake_deferred_bio_worker(struct cache *cache) queue_work(cache->wq, &cache->deferred_bio_worker); } -static void wake_deferred_writethrough_worker(struct cache *cache) -{ - queue_work(cache->wq, &cache->deferred_writethrough_worker); -} - static void wake_migration_worker(struct cache *cache) { if (passthrough_mode(&cache->features)) @@ -868,16 +864,23 @@ static void check_if_tick_bio_needed(struct cache *cache, struct bio *bio) spin_unlock_irqrestore(&cache->lock, flags); } -static void remap_to_origin_clear_discard(struct cache *cache, struct bio *bio, - dm_oblock_t oblock) +static void __remap_to_origin_clear_discard(struct cache *cache, struct bio *bio, + dm_oblock_t oblock, bool bio_has_pbd) { - // FIXME: this is called way too much. - check_if_tick_bio_needed(cache, bio); + if (bio_has_pbd) + check_if_tick_bio_needed(cache, bio); remap_to_origin(cache, bio); if (bio_data_dir(bio) == WRITE) clear_discard(cache, oblock_to_dblock(cache, oblock)); } +static void remap_to_origin_clear_discard(struct cache *cache, struct bio *bio, + dm_oblock_t oblock) +{ + // FIXME: check_if_tick_bio_needed() is called way too much through this interface + __remap_to_origin_clear_discard(cache, bio, oblock, true); +} + static void remap_to_cache_dirty(struct cache *cache, struct bio *bio, dm_oblock_t oblock, dm_cblock_t cblock) { @@ -937,57 +940,26 @@ static void issue_op(struct bio *bio, void *context) accounted_request(cache, bio); } -static void defer_writethrough_bio(struct cache *cache, struct bio *bio) -{ - unsigned long flags; - - spin_lock_irqsave(&cache->lock, flags); - bio_list_add(&cache->deferred_writethrough_bios, bio); - spin_unlock_irqrestore(&cache->lock, flags); - - wake_deferred_writethrough_worker(cache); -} - -static void writethrough_endio(struct bio *bio) -{ - struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT); - - dm_unhook_bio(&pb->hook_info, bio); - - if (bio->bi_status) { - bio_endio(bio); - return; - } - - dm_bio_restore(&pb->bio_details, bio); - remap_to_cache(pb->cache, bio, pb->cblock); - - /* - * We can't issue this bio directly, since we're in interrupt - * context. So it gets put on a bio list for processing by the - * worker thread. - */ - defer_writethrough_bio(pb->cache, bio); -} - /* - * FIXME: send in parallel, huge latency as is. * When running in writethrough mode we need to send writes to clean blocks - * to both the cache and origin devices. In future we'd like to clone the - * bio and send them in parallel, but for now we're doing them in - * series as this is easier. + * to both the cache and origin devices. Clone the bio and send them in parallel. */ -static void remap_to_origin_then_cache(struct cache *cache, struct bio *bio, - dm_oblock_t oblock, dm_cblock_t cblock) +static void remap_to_origin_and_cache(struct cache *cache, struct bio *bio, + dm_oblock_t oblock, dm_cblock_t cblock) { - struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT); + struct bio *origin_bio = bio_clone_fast(bio, GFP_NOIO, cache->bs); + + BUG_ON(!origin_bio); - pb->cache = cache; - pb->cblock = cblock; - dm_hook_bio(&pb->hook_info, bio, writethrough_endio, NULL); - dm_bio_record(&pb->bio_details, bio); + bio_chain(origin_bio, bio); + /* + * Passing false to __remap_to_origin_clear_discard() skips + * all code that might use per_bio_data (since clone doesn't have it) + */ + __remap_to_origin_clear_discard(cache, origin_bio, oblock, false); + submit_bio(origin_bio); - remap_to_origin_clear_discard(pb->cache, bio, oblock); + remap_to_cache(cache, bio, cblock); } /*---------------------------------------------------------------- @@ -1873,7 +1845,7 @@ static int map_bio(struct cache *cache, struct bio *bio, dm_oblock_t block, } else { if (bio_data_dir(bio) == WRITE && writethrough_mode(&cache->features) && !is_dirty(cache, cblock)) { - remap_to_origin_then_cache(cache, bio, block, cblock); + remap_to_origin_and_cache(cache, bio, block, cblock); accounted_begin(cache, bio); } else remap_to_cache_dirty(cache, bio, block, cblock); @@ -2132,6 +2104,9 @@ static void destroy(struct cache *cache) kfree(cache->ctr_args[i]); kfree(cache->ctr_args); + if (cache->bs) + bioset_free(cache->bs); + kfree(cache); } @@ -2589,6 +2564,13 @@ static int cache_create(struct cache_args *ca, struct cache **result) cache->features = ca->features; ti->per_io_data_size = get_per_bio_data_size(cache); + if (writethrough_mode(&cache->features)) { + /* Create bioset for writethrough bios issued to origin */ + cache->bs = bioset_create(BIO_POOL_SIZE, 0, 0); + if (!cache->bs) + goto bad; + } + cache->callbacks.congested_fn = cache_is_congested; dm_table_add_target_callbacks(ti->table, &cache->callbacks); -- 1.8.3.1