btrfs: simplify block group traversal in btrfs_put_block_group_cache

We're breaking out and re-searching for the next block group while
evicting any of the block group cache inodes.  This is not needed, the
block groups aren't disappearing here, we can simply loop through the
block groups like normal and iput any inode that we find.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/block-group.c

@@ -3950,36 +3950,24 @@ void btrfs_reserve_chunk_metadata(struct btrfs_trans_handle *trans,
 void btrfs_put_block_group_cache(struct btrfs_fs_info *info)
 {
 	struct btrfs_block_group *block_group;
-	u64 last = 0;
 
-	while (1) {
-		struct inode *inode;
-
-		block_group = btrfs_lookup_first_block_group(info, last);
-		while (block_group) {
-			btrfs_wait_block_group_cache_done(block_group);
-			spin_lock(&block_group->lock);
-			if (test_bit(BLOCK_GROUP_FLAG_IREF,
-				     &block_group->runtime_flags))
-				break;
+	block_group = btrfs_lookup_first_block_group(info, 0);
+	while (block_group) {
+		btrfs_wait_block_group_cache_done(block_group);
+		spin_lock(&block_group->lock);
+		if (test_and_clear_bit(BLOCK_GROUP_FLAG_IREF,
+				       &block_group->runtime_flags)) {
+			struct inode *inode = block_group->inode;
+
+			block_group->inode = NULL;
 			spin_unlock(&block_group->lock);
-			block_group = btrfs_next_block_group(block_group);
-		}
-		if (!block_group) {
-			if (last == 0)
-				break;
-			last = 0;
-			continue;
-		}
 
-		inode = block_group->inode;
-		clear_bit(BLOCK_GROUP_FLAG_IREF, &block_group->runtime_flags);
-		block_group->inode = NULL;
-		spin_unlock(&block_group->lock);
-		ASSERT(block_group->io_ctl.inode == NULL);
-		iput(inode);
-		last = block_group->start + block_group->length;
-		btrfs_put_block_group(block_group);
+			ASSERT(block_group->io_ctl.inode == NULL);
+			iput(inode);
+		} else {
+			spin_unlock(&block_group->lock);
+		}
+		block_group = btrfs_next_block_group(block_group);
 	}
 }