btrfs-progs: check: add support to clear v1 free space cache

Kernel clear_cache mount option will only rebuild free space cache if
the used space of that chunk has changed.

So it won't ensure any corrupted free space cache get cleared.

So add a new option "--clear-space-cache v1|v2" to btrfsck, to
completely wipe out free space cache.
So kernel won't complain again.

Reported-by: Ivan P <chrnosphered@gmail.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
[ adjusted error messages, doc wording changes ]
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 127 insertions, 0 deletions

diff --git a/free-space-cache.c b/free-space-cache.c
index 1919d90e..286b185e 100644
--- a/free-space-cache.c
+++ b/free-space-cache.c
@@ -25,6 +25,7 @@
 #include "crc32c.h"
 #include "bitops.h"
 #include "internal.h"
+#include "utils.h"
 
 /*
  * Kernel always uses PAGE_CACHE_SIZE for sectorsize, but we don't have
@@ -877,3 +878,129 @@ next:
 		prev = e;
 	}
 }
+
+int btrfs_clear_free_space_cache(struct btrfs_fs_info *fs_info,
+				 struct btrfs_block_group_cache *bg)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *tree_root = fs_info->tree_root;
+	struct btrfs_path path;
+	struct btrfs_key key;
+	struct btrfs_disk_key location;
+	struct btrfs_free_space_header *sc_header;
+	struct extent_buffer *node;
+	u64 ino;
+	int slot;
+	int ret;
+
+	trans = btrfs_start_transaction(tree_root, 1);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
+	btrfs_init_path(&path);
+
+	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+	key.type = 0;
+	key.offset = bg->key.objectid;
+
+	ret = btrfs_search_slot(trans, tree_root, &key, &path, -1, 1);
+	if (ret > 0) {
+		ret = 0;
+		goto out;
+	}
+	if (ret < 0)
+		goto out;
+
+	node = path.nodes[0];
+	slot = path.slots[0];
+	sc_header = btrfs_item_ptr(node, slot, struct btrfs_free_space_header);
+	btrfs_free_space_key(node, sc_header, &location);
+	ino = location.objectid;
+
+	/* Delete the free space header, as we have the ino to continue */
+	ret = btrfs_del_item(trans, tree_root, &path);
+	if (ret < 0) {
+		error("failed to remove free space header for block group %llu: %d",
+		      bg->key.objectid, ret);
+		goto out;
+	}
+	btrfs_release_path(&path);
+
+	/* Iterate from the end of the free space cache inode */
+	key.objectid = ino;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = (u64)-1;
+	ret = btrfs_search_slot(trans, tree_root, &key, &path, -1, 1);
+	if (ret < 0) {
+		error("failed to locate free space cache extent for block group %llu: %d",
+		      bg->key.objectid, ret);
+		goto out;
+	}
+	while (1) {
+		struct btrfs_file_extent_item *fi;
+		u64 disk_bytenr;
+		u64 disk_num_bytes;
+
+		ret = btrfs_previous_item(tree_root, &path, ino,
+					  BTRFS_EXTENT_DATA_KEY);
+		if (ret > 0) {
+			ret = 0;
+			break;
+		}
+		if (ret < 0) {
+			error(
+	"failed to locate free space cache extent for block group %llu: %d",
+				bg->key.objectid, ret);
+			goto out;
+		}
+		node = path.nodes[0];
+		slot = path.slots[0];
+		btrfs_item_key_to_cpu(node, &key, slot);
+		fi = btrfs_item_ptr(node, slot, struct btrfs_file_extent_item);
+		disk_bytenr = btrfs_file_extent_disk_bytenr(node, fi);
+		disk_num_bytes = btrfs_file_extent_disk_num_bytes(node, fi);
+
+		ret = btrfs_free_extent(trans, tree_root, disk_bytenr,
+					disk_num_bytes, 0, tree_root->objectid,
+					ino, key.offset);
+		if (ret < 0) {
+			error("failed to remove backref for disk bytenr %llu: %d",
+			      disk_bytenr, ret);
+			goto out;
+		}
+		ret = btrfs_del_item(trans, tree_root, &path);
+		if (ret < 0) {
+			error(
+	"failed to remove free space extent data for ino %llu offset %llu: %d",
+			      ino, key.offset, ret);
+			goto out;
+		}
+	}
+	btrfs_release_path(&path);
+
+	/* Now delete free space cache inode item */
+	key.objectid = ino;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot(trans, tree_root, &key, &path, -1, 1);
+	if (ret > 0)
+		warning("free space inode %llu not found, ignore", ino);
+	if (ret < 0) {
+		error(
+	"failed to locate free space cache inode %llu for block group %llu: %d",
+		      ino, bg->key.objectid, ret);
+		goto out;
+	}
+	ret = btrfs_del_item(trans, tree_root, &path);
+	if (ret < 0) {
+		error(
+	"failed to delete free space cache inode %llu for block group %llu: %d",
+		      ino, bg->key.objectid, ret);
+	}
+out:
+	btrfs_release_path(&path);
+	if (!ret)
+		btrfs_commit_transaction(trans, tree_root);
+	return ret;
+}