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authorJoe Thornber <ejt@redhat.com>2013-10-31 13:55:49 -0400
committerMike Snitzer <snitzer@redhat.com>2013-11-11 11:37:45 -0500
commitf494a9c6b1b6dd9a9f21bbb75d9210d478eeb498 (patch)
treee57197b7d38e7c6b2d718681fd70540ccc9a831e /drivers/md
parentc9d28d5d09a0fd5f02f1321c8e18ff7d9f92270b (diff)
dm cache: cache shrinking support
Allow a cache to shrink if the blocks being removed from the cache are not dirty. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-cache-metadata.c66
-rw-r--r--drivers/md/dm-cache-target.c63
2 files changed, 120 insertions, 9 deletions
diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index 2262b4e57a2..062b83ed3e8 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 655994fdf30..183dfc9db29 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) {