dm thin: dont use map_context

This patch removes endio_hook_pool from dm-thin and uses per-bio data instead.

This patch removes any use of map_info in preparation for the next patch
that removes map_info from bio-based device mapper.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-thin.c

@@ -186,7 +186,6 @@ struct pool {
 
 	struct dm_thin_new_mapping *next_mapping;
 	mempool_t *mapping_pool;
-	mempool_t *endio_hook_pool;
 
 	process_bio_fn process_bio;
 	process_bio_fn process_discard;
@@ -304,7 +303,7 @@ static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master)
 	bio_list_init(master);
 
 	while ((bio = bio_list_pop(&bios))) {
-		struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+		struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 
 		if (h->tc == tc)
 			bio_endio(bio, DM_ENDIO_REQUEUE);
@@ -375,7 +374,7 @@ static void inc_all_io_entry(struct pool *pool, struct bio *bio)
 	if (bio->bi_rw & REQ_DISCARD)
 		return;
 
-	h = dm_get_mapinfo(bio)->ptr;
+	h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 	h->all_io_entry = dm_deferred_entry_inc(pool->all_io_ds);
 }
 
@@ -485,7 +484,7 @@ static void copy_complete(int read_err, unsigned long write_err, void *context)
 static void overwrite_endio(struct bio *bio, int err)
 {
 	unsigned long flags;
-	struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+	struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 	struct dm_thin_new_mapping *m = h->overwrite_mapping;
 	struct pool *pool = m->tc->pool;
 
@@ -714,7 +713,7 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
 	 * bio immediately. Otherwise we use kcopyd to clone the data first.
 	 */
 	if (io_overwrites_block(pool, bio)) {
-		struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+		struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 
 		h->overwrite_mapping = m;
 		m->bio = bio;
@@ -784,7 +783,7 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
 		process_prepared_mapping(m);
 
 	else if (io_overwrites_block(pool, bio)) {
-		struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+		struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 
 		h->overwrite_mapping = m;
 		m->bio = bio;
@@ -899,7 +898,7 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
  */
 static void retry_on_resume(struct bio *bio)
 {
-	struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+	struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 	struct thin_c *tc = h->tc;
 	struct pool *pool = tc->pool;
 	unsigned long flags;
@@ -1051,7 +1050,7 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
 	if (bio_data_dir(bio) == WRITE && bio->bi_size)
 		break_sharing(tc, bio, block, &key, lookup_result, cell);
 	else {
-		struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+		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);
@@ -1226,7 +1225,7 @@ static void process_deferred_bios(struct pool *pool)
 	spin_unlock_irqrestore(&pool->lock, flags);
 
 	while ((bio = bio_list_pop(&bios))) {
-		struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+		struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 		struct thin_c *tc = h->tc;
 
 		/*
@@ -1359,17 +1358,14 @@ static void thin_defer_bio(struct thin_c *tc, struct bio *bio)
 	wake_worker(pool);
 }
 
-static struct dm_thin_endio_hook *thin_hook_bio(struct thin_c *tc, struct bio *bio)
+static void thin_hook_bio(struct thin_c *tc, struct bio *bio)
 {
-	struct pool *pool = tc->pool;
-	struct dm_thin_endio_hook *h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);
+	struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 
 	h->tc = tc;
 	h->shared_read_entry = NULL;
 	h->all_io_entry = NULL;
 	h->overwrite_mapping = NULL;
-
-	return h;
 }
 
 /*
@@ -1386,7 +1382,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio,
 	struct dm_bio_prison_cell *cell1, *cell2;
 	struct dm_cell_key key;
 
-	map_context->ptr = thin_hook_bio(tc, bio);
+	thin_hook_bio(tc, bio);
 
 	if (get_pool_mode(tc->pool) == PM_FAIL) {
 		bio_io_error(bio);
@@ -1595,14 +1591,12 @@ static void __pool_destroy(struct pool *pool)
 	if (pool->next_mapping)
 		mempool_free(pool->next_mapping, pool->mapping_pool);
 	mempool_destroy(pool->mapping_pool);
-	mempool_destroy(pool->endio_hook_pool);
 	dm_deferred_set_destroy(pool->shared_read_ds);
 	dm_deferred_set_destroy(pool->all_io_ds);
 	kfree(pool);
 }
 
 static struct kmem_cache *_new_mapping_cache;
-static struct kmem_cache *_endio_hook_cache;
 
 static struct pool *pool_create(struct mapped_device *pool_md,
 				struct block_device *metadata_dev,
@@ -1696,13 +1690,6 @@ static struct pool *pool_create(struct mapped_device *pool_md,
 		goto bad_mapping_pool;
 	}
 
-	pool->endio_hook_pool = mempool_create_slab_pool(ENDIO_HOOK_POOL_SIZE,
-							 _endio_hook_cache);
-	if (!pool->endio_hook_pool) {
-		*error = "Error creating pool's endio_hook mempool";
-		err_p = ERR_PTR(-ENOMEM);
-		goto bad_endio_hook_pool;
-	}
 	pool->ref_count = 1;
 	pool->last_commit_jiffies = jiffies;
 	pool->pool_md = pool_md;
@@ -1711,8 +1698,6 @@ static struct pool *pool_create(struct mapped_device *pool_md,
 
 	return pool;
 
-bad_endio_hook_pool:
-	mempool_destroy(pool->mapping_pool);
 bad_mapping_pool:
 	dm_deferred_set_destroy(pool->all_io_ds);
 bad_all_io_ds:
@@ -2607,6 +2592,7 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
 
 	ti->num_flush_requests = 1;
 	ti->flush_supported = true;
+	ti->per_bio_data_size = sizeof(struct dm_thin_endio_hook);
 
 	/* In case the pool supports discards, pass them on. */
 	if (tc->pool->pf.discard_enabled) {
@@ -2653,7 +2639,7 @@ static int thin_endio(struct dm_target *ti,
 		      union map_info *map_context)
 {
 	unsigned long flags;
-	struct dm_thin_endio_hook *h = map_context->ptr;
+	struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
 	struct list_head work;
 	struct dm_thin_new_mapping *m, *tmp;
 	struct pool *pool = h->tc->pool;
@@ -2683,8 +2669,6 @@ static int thin_endio(struct dm_target *ti,
 		}
 	}
 
-	mempool_free(h, pool->endio_hook_pool);
-
 	return 0;
 }
 
@@ -2813,14 +2797,8 @@ static int __init dm_thin_init(void)
 	if (!_new_mapping_cache)
 		goto bad_new_mapping_cache;
 
-	_endio_hook_cache = KMEM_CACHE(dm_thin_endio_hook, 0);
-	if (!_endio_hook_cache)
-		goto bad_endio_hook_cache;
-
 	return 0;
 
-bad_endio_hook_cache:
-	kmem_cache_destroy(_new_mapping_cache);
 bad_new_mapping_cache:
 	dm_unregister_target(&pool_target);
 bad_pool_target:
@@ -2835,7 +2813,6 @@ static void dm_thin_exit(void)
 	dm_unregister_target(&pool_target);
 
 	kmem_cache_destroy(_new_mapping_cache);
-	kmem_cache_destroy(_endio_hook_cache);
 }
 
 module_init(dm_thin_init);