Commit eb2aa48d authored by Joe Thornber's avatar Joe Thornber Committed by Alasdair G Kergon
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dm thin: prepare to support discard 



This patch contains the ground work needed for dm-thin to support discard.

  - Adds endio function that replaces shared_read_endio.

  - Introduce an explicit 'quiesced' flag into the new_mapping structure.
    Before, this was implicitly indicated by m->list being empty.

  - The map_info->ptr remains constant for the duration of a bio's trip
    through the thin target.  Make it easier to reason about it.

Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 6efd6e83

drivers/md/dm-thin.c

+72 −53
Original line number Diff line number Diff line
@@ -523,7 +523,7 @@ struct pool { 


	struct bio_list retry_on_resume_list;



	struct deferred_set ds;	/* FIXME: move to thin_c */

	struct deferred_set shared_read_ds;



	struct new_mapping *next_mapping;

	mempool_t *mapping_pool;
@@ -618,6 +618,12 @@ static struct pool *__pool_table_lookup_metadata_dev(struct block_device *md_dev 


/*----------------------------------------------------------------*/



struct endio_hook {

	struct thin_c *tc;

	struct deferred_entry *shared_read_entry;

	struct new_mapping *overwrite_mapping;

};



static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master)

{

	struct bio *bio;
@@ -628,7 +634,8 @@ static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master) 
	bio_list_init(master);



	while ((bio = bio_list_pop(&bios))) {

		if (dm_get_mapinfo(bio)->ptr == tc)

		struct endio_hook *h = dm_get_mapinfo(bio)->ptr;

		if (h->tc == tc)

			bio_endio(bio, DM_ENDIO_REQUEUE);

		else

			bio_list_add(master, bio);
@@ -716,16 +723,11 @@ static void wake_worker(struct pool *pool) 
/*

 * Bio endio functions.

 */

struct endio_hook {

	struct thin_c *tc;

	bio_end_io_t *saved_bi_end_io;

	struct deferred_entry *entry;

};



struct new_mapping {

	struct list_head list;



	int prepared;

	unsigned quiesced:1;

	unsigned prepared:1;



	struct thin_c *tc;

	dm_block_t virt_block;
@@ -747,7 +749,7 @@ static void __maybe_add_mapping(struct new_mapping *m) 
{

	struct pool *pool = m->tc->pool;



	if (list_empty(&m->list) && m->prepared) {

	if (m->quiesced && m->prepared) {

		list_add(&m->list, &pool->prepared_mappings);

		wake_worker(pool);

	}
@@ -770,7 +772,8 @@ 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 new_mapping *m = dm_get_mapinfo(bio)->ptr;

	struct endio_hook *h = dm_get_mapinfo(bio)->ptr;

	struct new_mapping *m = h->overwrite_mapping;

	struct pool *pool = m->tc->pool;



	m->err = err;
@@ -781,31 +784,6 @@ static void overwrite_endio(struct bio *bio, int err) 
	spin_unlock_irqrestore(&pool->lock, flags);

}



static void shared_read_endio(struct bio *bio, int err)

{

	struct list_head mappings;

	struct new_mapping *m, *tmp;

	struct endio_hook *h = dm_get_mapinfo(bio)->ptr;

	unsigned long flags;

	struct pool *pool = h->tc->pool;



	bio->bi_end_io = h->saved_bi_end_io;

	bio_endio(bio, err);



	INIT_LIST_HEAD(&mappings);

	ds_dec(h->entry, &mappings);



	spin_lock_irqsave(&pool->lock, flags);

	list_for_each_entry_safe(m, tmp, &mappings, list) {

		list_del(&m->list);

		INIT_LIST_HEAD(&m->list);

		__maybe_add_mapping(m);

	}

	spin_unlock_irqrestore(&pool->lock, flags);



	mempool_free(h, pool->endio_hook_pool);

}



/*----------------------------------------------------------------*/



/*
@@ -957,6 +935,7 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block, 
	struct new_mapping *m = get_next_mapping(pool);



	INIT_LIST_HEAD(&m->list);

	m->quiesced = 0;

	m->prepared = 0;

	m->tc = tc;

	m->virt_block = virt_block;
@@ -965,7 +944,8 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block, 
	m->err = 0;

	m->bio = NULL;



	ds_add_work(&pool->ds, &m->list);

	if (!ds_add_work(&pool->shared_read_ds, &m->list))

		m->quiesced = 1;



	/*

	 * IO to pool_dev remaps to the pool target's data_dev.
@@ -974,9 +954,10 @@ 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 endio_hook *h = dm_get_mapinfo(bio)->ptr;

		h->overwrite_mapping = m;

		m->bio = bio;

		save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);

		dm_get_mapinfo(bio)->ptr = m;

		remap_and_issue(tc, bio, data_dest);

	} else {

		struct dm_io_region from, to;
@@ -1023,6 +1004,7 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block, 
	struct new_mapping *m = get_next_mapping(pool);



	INIT_LIST_HEAD(&m->list);

	m->quiesced = 1;

	m->prepared = 0;

	m->tc = tc;

	m->virt_block = virt_block;
@@ -1040,9 +1022,10 @@ 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 endio_hook *h = dm_get_mapinfo(bio)->ptr;

		h->overwrite_mapping = m;

		m->bio = bio;

		save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);

		dm_get_mapinfo(bio)->ptr = m;

		remap_and_issue(tc, bio, data_block);



	} else {
@@ -1129,7 +1112,8 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result) 
 */

static void retry_on_resume(struct bio *bio)

{

	struct thin_c *tc = dm_get_mapinfo(bio)->ptr;

	struct endio_hook *h = dm_get_mapinfo(bio)->ptr;

	struct thin_c *tc = h->tc;

	struct pool *pool = tc->pool;

	unsigned long flags;
@@ -1195,13 +1179,9 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio, 
	if (bio_data_dir(bio) == WRITE)

		break_sharing(tc, bio, block, &key, lookup_result, cell);

	else {

		struct endio_hook *h;

		h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);

		struct endio_hook *h = dm_get_mapinfo(bio)->ptr;



		h->tc = tc;

		h->entry = ds_inc(&pool->ds);

		save_and_set_endio(bio, &h->saved_bi_end_io, shared_read_endio);

		dm_get_mapinfo(bio)->ptr = h;

		h->shared_read_entry = ds_inc(&pool->shared_read_ds);



		cell_release_singleton(cell, bio);

		remap_and_issue(tc, bio, lookup_result->block);
@@ -1325,7 +1305,9 @@ static void process_deferred_bios(struct pool *pool) 
	spin_unlock_irqrestore(&pool->lock, flags);



	while ((bio = bio_list_pop(&bios))) {

		struct thin_c *tc = dm_get_mapinfo(bio)->ptr;

		struct endio_hook *h = dm_get_mapinfo(bio)->ptr;

		struct thin_c *tc = h->tc;



		/*

		 * If we've got no free new_mapping structs, and processing

		 * this bio might require one, we pause until there are some
@@ -1408,6 +1390,18 @@ static void thin_defer_bio(struct thin_c *tc, struct bio *bio) 
	wake_worker(pool);

}



static struct endio_hook *thin_hook_bio(struct thin_c *tc, struct bio *bio)

{

	struct pool *pool = tc->pool;

	struct endio_hook *h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);



	h->tc = tc;

	h->shared_read_entry = NULL;

	h->overwrite_mapping = NULL;



	return h;

}



/*

 * Non-blocking function called from the thin target's map function.

 */
@@ -1420,11 +1414,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio, 
	struct dm_thin_device *td = tc->td;

	struct dm_thin_lookup_result result;



	/*

	 * Save the thin context for easy access from the deferred bio later.

	 */

	map_context->ptr = tc;



	map_context->ptr = thin_hook_bio(tc, bio);

	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {

		thin_defer_bio(tc, bio);

		return DM_MAPIO_SUBMITTED;
@@ -1604,7 +1594,7 @@ static struct pool *pool_create(struct mapped_device *pool_md, 
	pool->low_water_triggered = 0;

	pool->no_free_space = 0;

	bio_list_init(&pool->retry_on_resume_list);

	ds_init(&pool->ds);

	ds_init(&pool->shared_read_ds);



	pool->next_mapping = NULL;

	pool->mapping_pool =
@@ -2394,6 +2384,34 @@ static int thin_map(struct dm_target *ti, struct bio *bio, 
	return thin_bio_map(ti, bio, map_context);

}



static int thin_endio(struct dm_target *ti,

		      struct bio *bio, int err,

		      union map_info *map_context)

{

	unsigned long flags;

	struct endio_hook *h = map_context->ptr;

	struct list_head work;

	struct new_mapping *m, *tmp;

	struct pool *pool = h->tc->pool;



	if (h->shared_read_entry) {

		INIT_LIST_HEAD(&work);

		ds_dec(h->shared_read_entry, &work);



		spin_lock_irqsave(&pool->lock, flags);

		list_for_each_entry_safe(m, tmp, &work, list) {

			list_del(&m->list);

			m->quiesced = 1;

			__maybe_add_mapping(m);

		}

		spin_unlock_irqrestore(&pool->lock, flags);

	}



	mempool_free(h, pool->endio_hook_pool);



	return 0;

}



static void thin_postsuspend(struct dm_target *ti)

{

	if (dm_noflush_suspending(ti))
@@ -2481,6 +2499,7 @@ static struct target_type thin_target = { 
	.ctr = thin_ctr,

	.dtr = thin_dtr,

	.map = thin_map,

	.end_io = thin_endio,

	.postsuspend = thin_postsuspend,

	.status = thin_status,

	.iterate_devices = thin_iterate_devices,

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