[1/6] dm cache: cache shrinking support

Message ID	1384190448-3861-2-git-send-email-snitzer@redhat.com (mailing list archive)
State	Accepted, archived
Delegated to:	Mike Snitzer
Headers	show Return-Path: <dm-devel-bounces@redhat.com> From: Mike Snitzer <snitzer@redhat.com> To: dm-devel@redhat.com Date: Mon, 11 Nov 2013 12:20:43 -0500 Message-Id: <1384190448-3861-2-git-send-email-snitzer@redhat.com> In-Reply-To: <1384190448-3861-1-git-send-email-snitzer@redhat.com> References: <1384190448-3861-1-git-send-email-snitzer@redhat.com> Subject: [dm-devel] [PATCH 1/6] dm cache: cache shrinking support Precedence: junk Reply-To: device-mapper development <dm-devel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c index 2262b4e..062b83e 100644 --- a/drivers/md/dm-cache-metadata.c +++ b/drivers/md/dm-cache-metadata.c @@ -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; diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 655994f..183dfc9 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -2502,26 +2502,71 @@ static int load_discard(void *context, sector_t discard_block_size, return 0; } +static dm_cblock_t get_cache_dev_size(struct cache *cache) +{ + 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; + + /* + * We can't drop a dirty block when shrinking the cache. + */ + 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) { + DMERR("could not resize cache metadata"); + 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; - sector_t actual_cache_size = get_dev_size(cache->cache_dev); - (void) sector_div(actual_cache_size, cache->sectors_per_block); + dm_cblock_t csize = get_cache_dev_size(cache); /* * Check to see if the cache has resized. */ - if (from_cblock(cache->cache_size) != actual_cache_size || !cache->sized) { - cache->cache_size = to_cblock(actual_cache_size); - - r = dm_cache_resize(cache->cmd, cache->cache_size); - if (r) { - DMERR("could not resize cache metadata"); + 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) {

[1/6] dm cache: cache shrinking support

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