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Commit f494a9c6 authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
Browse files

dm cache: cache shrinking support 



Allow a cache to shrink if the blocks being removed from the cache are
not dirty.

Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent c9d28d5d

drivers/md/dm-cache-metadata.c

+66 −0
Original line number Diff line number Diff line
@@ -667,19 +667,85 @@ void dm_cache_metadata_close(struct dm_cache_metadata *cmd) 
	kfree(cmd);

}



/*

 * Checks that the given cache block is either unmapped or clean.

 */

static int block_unmapped_or_clean(struct dm_cache_metadata *cmd, dm_cblock_t b,

				   bool *result)

{

	int r;

	__le64 value;

	dm_oblock_t ob;

	unsigned flags;



	r = dm_array_get_value(&cmd->info, cmd->root, from_cblock(b), &value);

	if (r) {

		DMERR("block_unmapped_or_clean failed");

		return r;

	}



	unpack_value(value, &ob, &flags);

	*result = !((flags & M_VALID) && (flags & M_DIRTY));



	return 0;

}



static int blocks_are_unmapped_or_clean(struct dm_cache_metadata *cmd,

					dm_cblock_t begin, dm_cblock_t end,

					bool *result)

{

	int r;

	*result = true;



	while (begin != end) {

		r = block_unmapped_or_clean(cmd, begin, result);

		if (r)

			return r;



		if (!*result) {

			DMERR("cache block %llu is dirty",

			      (unsigned long long) from_cblock(begin));

			return 0;

		}



		begin = to_cblock(from_cblock(begin) + 1);

	}



	return 0;

}



int dm_cache_resize(struct dm_cache_metadata *cmd, dm_cblock_t new_cache_size)

{

	int r;

	bool clean;

	__le64 null_mapping = pack_value(0, 0);



	down_write(&cmd->root_lock);

	__dm_bless_for_disk(&null_mapping);



	if (from_cblock(new_cache_size) < from_cblock(cmd->cache_blocks)) {

		r = blocks_are_unmapped_or_clean(cmd, new_cache_size, cmd->cache_blocks, &clean);

		if (r) {

			__dm_unbless_for_disk(&null_mapping);

			goto out;

		}



		if (!clean) {

			DMERR("unable to shrink cache due to dirty blocks");

			r = -EINVAL;

			__dm_unbless_for_disk(&null_mapping);

			goto out;

		}

	}



	r = dm_array_resize(&cmd->info, cmd->root, from_cblock(cmd->cache_blocks),

			    from_cblock(new_cache_size),

			    &null_mapping, &cmd->root);

	if (!r)

		cmd->cache_blocks = new_cache_size;

	cmd->changed = true;



out:

	up_write(&cmd->root_lock);



	return r;

drivers/md/dm-cache-target.c

+54 −9
Original line number Diff line number Diff line
@@ -2502,18 +2502,36 @@ static int load_discard(void *context, sector_t discard_block_size, 
	return 0;

}



static int cache_preresume(struct dm_target *ti)

static dm_cblock_t get_cache_dev_size(struct cache *cache)

{

	int r = 0;

	struct cache *cache = ti->private;

	sector_t actual_cache_size = get_dev_size(cache->cache_dev);

	(void) sector_div(actual_cache_size, cache->sectors_per_block);

	sector_t size = get_dev_size(cache->cache_dev);

	(void) sector_div(size, cache->sectors_per_block);

	return to_cblock(size);

}



static bool can_resize(struct cache *cache, dm_cblock_t new_size)

{

	if (from_cblock(new_size) > from_cblock(cache->cache_size))

		return true;



	/*

	 * Check to see if the cache has resized.

	 * We can't drop a dirty block when shrinking the cache.

	 */

	if (from_cblock(cache->cache_size) != actual_cache_size || !cache->sized) {

		cache->cache_size = to_cblock(actual_cache_size);

	while (from_cblock(new_size) < from_cblock(cache->cache_size)) {

		new_size = to_cblock(from_cblock(new_size) + 1);

		if (is_dirty(cache, new_size)) {

			DMERR("unable to shrink cache; cache block %llu is dirty",

			      (unsigned long long) from_cblock(new_size));

			return false;

		}

	}



	return true;

}



static int resize_cache_dev(struct cache *cache, dm_cblock_t new_size)

{

	int r;



	r = dm_cache_resize(cache->cmd, cache->cache_size);

	if (r) {
@@ -2521,7 +2539,34 @@ static int cache_preresume(struct dm_target *ti) 
		return r;

	}



	cache->cache_size = new_size;



	return 0;

}



static int cache_preresume(struct dm_target *ti)

{

	int r = 0;

	struct cache *cache = ti->private;

	dm_cblock_t csize = get_cache_dev_size(cache);



	/*

	 * Check to see if the cache has resized.

	 */

	if (!cache->sized) {

		r = resize_cache_dev(cache, csize);

		if (r)

			return r;



		cache->sized = true;



	} else if (csize != cache->cache_size) {

		if (!can_resize(cache, csize))

			return -EINVAL;



		r = resize_cache_dev(cache, csize);

		if (r)

			return r;

	}



	if (!cache->loaded_mappings) {