Btrfs: load free space cache if it exists

This patch actually loads the free space cache if it exists.  The only thing
that really changes here is that we need to cache the block group if we're going
to remove an extent from it.  Previously we did not do this since the caching
kthread would pick it up.  With the on disk cache we don't have this luxury so
we need to make sure we read the on disk cache in first, and then remove the
extent, that way when the extent is unpinned the free space is added to the
block group.  This has been tested with all sorts of things.

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 47 insertions, 3 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d5455a2bf60b..9a325e465ad9 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -421,7 +421,9 @@ err:
 	return 0;
 }
 
-static int cache_block_group(struct btrfs_block_group_cache *cache)
+static int cache_block_group(struct btrfs_block_group_cache *cache,
+			     struct btrfs_trans_handle *trans,
+			     int load_cache_only)
 {
 	struct btrfs_fs_info *fs_info = cache->fs_info;
 	struct btrfs_caching_control *caching_ctl;
@@ -432,6 +434,36 @@ static int cache_block_group(struct btrfs_block_group_cache *cache)
 	if (cache->cached != BTRFS_CACHE_NO)
 		return 0;
 
+	/*
+	 * We can't do the read from on-disk cache during a commit since we need
+	 * to have the normal tree locking.
+	 */
+	if (!trans->transaction->in_commit) {
+		spin_lock(&cache->lock);
+		if (cache->cached != BTRFS_CACHE_NO) {
+			spin_unlock(&cache->lock);
+			return 0;
+		}
+		cache->cached = BTRFS_CACHE_STARTED;
+		spin_unlock(&cache->lock);
+
+		ret = load_free_space_cache(fs_info, cache);
+
+		spin_lock(&cache->lock);
+		if (ret == 1) {
+			cache->cached = BTRFS_CACHE_FINISHED;
+			cache->last_byte_to_unpin = (u64)-1;
+		} else {
+			cache->cached = BTRFS_CACHE_NO;
+		}
+		spin_unlock(&cache->lock);
+		if (ret == 1)
+			return 0;
+	}
+
+	if (load_cache_only)
+		return 0;
+
 	caching_ctl = kzalloc(sizeof(*caching_ctl), GFP_KERNEL);
 	BUG_ON(!caching_ctl);
 
@@ -3984,6 +4016,14 @@ static int update_block_group(struct btrfs_trans_handle *trans,
 			factor = 2;
 		else
 			factor = 1;
+		/*
+		 * If this block group has free space cache written out, we
+		 * need to make sure to load it if we are removing space.  This
+		 * is because we need the unpinning stage to actually add the
+		 * space back to the block group, otherwise we will leak space.
+		 */
+		if (!alloc && cache->cached == BTRFS_CACHE_NO)
+			cache_block_group(cache, trans, 1);
 
 		byte_in_group = bytenr - cache->key.objectid;
 		WARN_ON(byte_in_group > cache->key.offset);
@@ -4828,6 +4868,10 @@ have_block_group:
 		if (unlikely(block_group->cached == BTRFS_CACHE_NO)) {
 			u64 free_percent;
 
+			ret = cache_block_group(block_group, trans, 1);
+			if (block_group->cached == BTRFS_CACHE_FINISHED)
+				goto have_block_group;
+
 			free_percent = btrfs_block_group_used(&block_group->item);
 			free_percent *= 100;
 			free_percent = div64_u64(free_percent,
@@ -4848,7 +4892,7 @@ have_block_group:
 			if (loop > LOOP_CACHING_NOWAIT ||
 			    (loop > LOOP_FIND_IDEAL &&
 			     atomic_read(&space_info->caching_threads) < 2)) {
-				ret = cache_block_group(block_group);
+				ret = cache_block_group(block_group, trans, 0);
 				BUG_ON(ret);
 			}
 			found_uncached_bg = true;
@@ -5405,7 +5449,7 @@ int btrfs_alloc_logged_file_extent(struct btrfs_trans_handle *trans,
 	u64 num_bytes = ins->offset;
 
 	block_group = btrfs_lookup_block_group(root->fs_info, ins->objectid);
-	cache_block_group(block_group);
+	cache_block_group(block_group, trans, 0);
 	caching_ctl = get_caching_control(block_group);
 
 	if (!caching_ctl) {