btrfs-progs: check: add repair functionality for orphan dev extents

There is a bug report that btrfs-check --repair didn't repair an orphan
dev extent, which makes kernel to reject the fs due to the overly strict
chunk related checks.

However for btrfs-check, it's pretty easy to remove orphan device
extents (which do not have corresponding chunks), and update the device
item to reflect the used_bytes changes.

Add a repair function, btrfs_remove_dev_extent() which does the repair,
and call that function for both original and lowmem modes.

Pull-request: #1043
Signed-off-by: Qu Wenruo <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: adam900710

check/main.c

@@ -8601,7 +8601,11 @@ int check_chunks(struct cache_tree *chunk_cache,
 				dext_rec->objectid,
 				dext_rec->offset,
 				dext_rec->length);
-		if (!ret)
+		err = -ENOENT;
+		if (opt_check_repair)
+			err = btrfs_remove_dev_extent(gfs_info, dext_rec->objectid,
+						      dext_rec->offset);
+		if (err && !ret)
 			ret = 1;
 	}
 	return ret;

check/mode-lowmem.c

@@ -4749,7 +4749,12 @@ static int check_dev_extent_item(struct extent_buffer *eb, int slot)
 		error(
 		"device extent[%llu, %llu, %llu] did not find the related chunk",
 			devext_key.objectid, devext_key.offset, length);
-		return REFERENCER_MISSING;
+		ret = -ENOENT;
+		if (opt_check_repair)
+			ret = btrfs_remove_dev_extent(gfs_info, devext_key.objectid,
+						      devext_key.offset);
+		if (ret < 0)
+			return REFERENCER_MISSING;
 	}
 	return 0;
 }

check/repair.c

@@ -31,7 +31,9 @@
 #include "kernel-shared/extent_io.h"
 #include "kernel-shared/disk-io.h"
 #include "kernel-shared/tree-checker.h"
+#include "kernel-shared/volumes.h"
 #include "common/extent-cache.h"
+#include "common/messages.h"
 #include "check/repair.h"
 
 int opt_check_repair = 0;
@@ -354,6 +356,82 @@ int btrfs_fix_block_accounting(struct btrfs_trans_handle *trans)
 	return ret;
 }
 
+int btrfs_remove_dev_extent(struct btrfs_fs_info *fs_info, u64 devid, u64 physical)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *dev_root = fs_info->dev_root;
+	struct btrfs_key key = {
+		.objectid = devid,
+		.type = BTRFS_DEV_EXTENT_KEY,
+		.offset = physical,
+	};
+	struct btrfs_path path = { 0 };
+	struct btrfs_dev_extent *dext;
+	struct btrfs_device *dev;
+	u64 length;
+	int ret;
+
+	dev = btrfs_find_device_by_devid(fs_info->fs_devices, devid, 0);
+	if (!dev) {
+		ret = -ENOENT;
+		error("failed to find devid %llu", devid);
+		return ret;
+	}
+	trans = btrfs_start_transaction(dev_root, 1);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		errno = -ret;
+		error_msg(ERROR_MSG_START_TRANS, "%m");
+		return ret;
+	}
+	ret = btrfs_search_slot(trans, dev_root, &key, &path, -1, 1);
+	if (ret > 0)
+		ret = -ENOENT;
+	if (ret < 0) {
+		errno = -ret;
+		error("failed to locate dev extent, devid %llu physical %llu: %m",
+		      devid, physical);
+		goto abort;
+	}
+	dext = btrfs_item_ptr(path.nodes[0], path.slots[0], struct btrfs_dev_extent);
+	length = btrfs_dev_extent_length(path.nodes[0], dext);
+	ret = btrfs_del_item(trans, dev_root, &path);
+	if (ret < 0) {
+		errno = -ret;
+		error("failed to delete dev extent, devid %llu physical %llu: %m",
+		      devid, physical);
+		goto abort;
+	}
+	btrfs_release_path(&path);
+	if (dev->bytes_used < length) {
+		warning("devid %llu has bytes_used %llu, smaller than %llu",
+			devid, dev->bytes_used, length);
+		dev->bytes_used = 0;
+	} else {
+		dev->bytes_used -= length;
+	}
+	ret = btrfs_update_device(trans, dev);
+	if (ret < 0) {
+		errno = -ret;
+		error("failed to update device, devid %llu: %m", devid);
+		goto abort;
+	}
+	ret = btrfs_commit_transaction(trans, dev_root);
+	if (ret < 0) {
+		errno = -ret;
+		error_msg(ERROR_MSG_COMMIT_TRANS, "%m");
+	} else {
+		printf("removed orphan dev extent, devid %llu physical %llu length %llu\n",
+			devid, physical, length);
+	}
+	return ret;
+
+abort:
+	btrfs_release_path(&path);
+	btrfs_abort_transaction(trans, ret);
+	return ret;
+}
+
 enum btrfs_tree_block_status btrfs_check_block_for_repair(struct extent_buffer *eb,
 							  struct btrfs_key *first_key)
 {

check/repair.h

@@ -48,6 +48,7 @@ int btrfs_mark_used_tree_blocks(struct btrfs_fs_info *fs_info,
 				struct extent_io_tree *tree);
 int btrfs_mark_used_blocks(struct btrfs_fs_info *fs_info,
 			   struct extent_io_tree *tree);
+int btrfs_remove_dev_extent(struct btrfs_fs_info *fs_info, u64 devid, u64 physical);
 enum btrfs_tree_block_status btrfs_check_block_for_repair(struct extent_buffer *eb,
 							  struct btrfs_key *first_key);
 void btrfs_set_item_key_unsafe(struct btrfs_root *root, struct btrfs_path *path,