[PATCH 4.14 227/228] dm cache: remove all obsolete writethrough-specific code

From: Greg Kroah-Hartman
Date: Thu Aug 20 2020 - 06:43:02 EST


From: Mike Snitzer <snitzer@xxxxxxxxxx>

commit 9958f1d9a04efb3db19134482b3f4c6897e0e7b8 upstream.

Now that the writethrough code is much simpler there is no need to track
so much state or cascade bio submission (as was done, via
writethrough_endio(), to issue origin then cache IO in series).

As such the obsolete writethrough list and workqueue is also removed.

Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/md/dm-cache-target.c | 82 -------------------------------------------
1 file changed, 1 insertion(+), 81 deletions(-)

--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -410,7 +410,6 @@ struct cache {
spinlock_t lock;
struct list_head deferred_cells;
struct bio_list deferred_bios;
- struct bio_list deferred_writethrough_bios;
sector_t migration_threshold;
wait_queue_head_t migration_wait;
atomic_t nr_allocated_migrations;
@@ -446,7 +445,6 @@ struct cache {
struct dm_kcopyd_client *copier;
struct workqueue_struct *wq;
struct work_struct deferred_bio_worker;
- struct work_struct deferred_writethrough_worker;
struct work_struct migration_worker;
struct delayed_work waker;
struct dm_bio_prison_v2 *prison;
@@ -491,15 +489,6 @@ struct per_bio_data {
struct dm_bio_prison_cell_v2 *cell;
struct dm_hook_info hook_info;
sector_t len;
-
- /*
- * writethrough fields. These MUST remain at the end of this
- * structure and the 'cache' member must be the first as it
- * is used to determine the offset of the writethrough fields.
- */
- struct cache *cache;
- dm_cblock_t cblock;
- struct dm_bio_details bio_details;
};

struct dm_cache_migration {
@@ -538,11 +527,6 @@ static void wake_deferred_bio_worker(str
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))
@@ -619,15 +603,9 @@ static unsigned lock_level(struct bio *b
* Per bio data
*--------------------------------------------------------------*/

-/*
- * If using writeback, leave out struct per_bio_data's writethrough fields.
- */
-#define PB_DATA_SIZE_WB (offsetof(struct per_bio_data, cache))
-#define PB_DATA_SIZE_WT (sizeof(struct per_bio_data))
-
static size_t get_per_bio_data_size(struct cache *cache)
{
- return writethrough_mode(cache) ? PB_DATA_SIZE_WT : PB_DATA_SIZE_WB;
+ return sizeof(struct per_bio_data);
}

static struct per_bio_data *get_per_bio_data(struct bio *bio, size_t data_size)
@@ -945,39 +923,6 @@ static void issue_op(struct bio *bio, vo
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);
-}
-
/*
* When running in writethrough mode we need to send writes to clean blocks
* to both the cache and origin devices. Clone the bio and send them in parallel.
@@ -2013,28 +1958,6 @@ static void process_deferred_bios(struct
schedule_commit(&cache->committer);
}

-static void process_deferred_writethrough_bios(struct work_struct *ws)
-{
- struct cache *cache = container_of(ws, struct cache, deferred_writethrough_worker);
-
- unsigned long flags;
- struct bio_list bios;
- struct bio *bio;
-
- bio_list_init(&bios);
-
- spin_lock_irqsave(&cache->lock, flags);
- bio_list_merge(&bios, &cache->deferred_writethrough_bios);
- bio_list_init(&cache->deferred_writethrough_bios);
- spin_unlock_irqrestore(&cache->lock, flags);
-
- /*
- * These bios have already been through accounted_begin()
- */
- while ((bio = bio_list_pop(&bios)))
- generic_make_request(bio);
-}
-
/*----------------------------------------------------------------
* Main worker loop
*--------------------------------------------------------------*/
@@ -2690,7 +2613,6 @@ static int cache_create(struct cache_arg
spin_lock_init(&cache->lock);
INIT_LIST_HEAD(&cache->deferred_cells);
bio_list_init(&cache->deferred_bios);
- bio_list_init(&cache->deferred_writethrough_bios);
atomic_set(&cache->nr_allocated_migrations, 0);
atomic_set(&cache->nr_io_migrations, 0);
init_waitqueue_head(&cache->migration_wait);
@@ -2729,8 +2651,6 @@ static int cache_create(struct cache_arg
goto bad;
}
INIT_WORK(&cache->deferred_bio_worker, process_deferred_bios);
- INIT_WORK(&cache->deferred_writethrough_worker,
- process_deferred_writethrough_bios);
INIT_WORK(&cache->migration_worker, check_migrations);
INIT_DELAYED_WORK(&cache->waker, do_waker);