This mail needs to be saent to stable@vger.kernel.org (now cc'd).
Greg et al: please backport 2df3bae9a6543e90042291707b8db0cbfbae9ee9
Thanks, Mike
On Mon, Jul 27 2020 at 9:40am -0400, John Donnelly John.P.donnelly@oracle.com wrote:
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: 705559706d62038b74c5088114c1799cf2c9dce8 (dm bio record: save/restore bi_end_io and bi_integrity, version 4.14.188)
70555970 introduced a mkfs.ext4 hang on a LVM device that has been modified with lvconvert --cachemode=writethrough.
Signed-off-by: John Donnelly john.p.donnelly@oracle.com Tested-by: John Donnelly john.p.donnelly@oracle.com Reviewed-by: Somasundaram Krishnasamy somasundaram.krishnasamy@oracle.com
conflict: drivers/md/dm-cache-target.c - Corrected syntax of writethrough_mode(&cache->feature) that was caught by arm compiler.
cc: stable@vger.kernel.org cc: snitzer@redhat.com
drivers/md/dm-cache-target.c | 54 ++++++++++++++++++++++++------------ 1 file changed, 37 insertions(+), 17 deletions(-)
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 69cdb29ef6be..8241b7c36655 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; @@ -868,16 +869,23 @@ 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) { @@ -971,23 +979,25 @@ static void writethrough_endio(struct bio *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);
- pb->cache = cache;
- pb->cblock = cblock;
- dm_hook_bio(&pb->hook_info, bio, writethrough_endio, NULL);
- dm_bio_record(&pb->bio_details, bio);
- BUG_ON(!origin_bio);
- remap_to_origin_clear_discard(pb->cache, bio, oblock);
- 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_cache(cache, bio, cblock);
} /*---------------------------------------------------------------- @@ -1873,7 +1883,7 @@ 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 +2142,9 @@ 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 +2602,13 @@ 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);
-- 2.26.2