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>
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 @@
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) {