Re: [PATCH v2 3/6] btrfs-progs: fix-data-checksum: show affected files

[David Sterba <dsterba@suse.cz>]

On Thu, May 15, 2025 at 05:30:18PM +0930, Qu Wenruo wrote:
> Previously "btrfs rescue fix-data-checksum" only show affected logical
> bytenr, which is not helpful to determine which files are affected.
> 
> Enhance the output by also outputting the affected subvolumes (in
> numeric form), and the file paths inside that subvolume.
> 
> The example looks like this:
> 
>   logical=13631488 corrtuped mirrors=1 affected files:
>     (subvolume 5)/foo
>     (subvolume 5)/dir/bar
>   logical=13635584 corrtuped mirrors=1 affected files:
>     (subvolume 5)/foo
>     (subvolume 5)/dir/bar
> 
> Although the end result is still not perfect, it's still much easier to
> find out which files are affected.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  cmds/rescue-fix-data-checksum.c | 59 +++++++++++++++++++++++++++++++--
>  1 file changed, 56 insertions(+), 3 deletions(-)
> 
> diff --git a/cmds/rescue-fix-data-checksum.c b/cmds/rescue-fix-data-checksum.c
> index 7e613ba57f76..bf3a65b31c71 100644
> --- a/cmds/rescue-fix-data-checksum.c
> +++ b/cmds/rescue-fix-data-checksum.c
> @@ -18,6 +18,7 @@
>  #include "kernel-shared/disk-io.h"
>  #include "kernel-shared/ctree.h"
>  #include "kernel-shared/volumes.h"
> +#include "kernel-shared/backref.h"
>  #include "common/messages.h"
>  #include "common/open-utils.h"
>  #include "cmds/rescue.h"
> @@ -158,6 +159,49 @@ static int iterate_one_csum_item(struct btrfs_fs_info *fs_info, struct btrfs_pat
>  	return ret;
>  }
>  
> +static int print_filenames(u64 ino, u64 offset, u64 rootid, void *ctx)
> +{
> +	struct btrfs_fs_info *fs_info = ctx;
> +	struct btrfs_root *root;
> +	struct btrfs_key key;
> +	struct inode_fs_paths *ipath;
> +	struct btrfs_path path = { 0 };
> +	int ret;
> +
> +	key.objectid = rootid;
> +	key.type = BTRFS_ROOT_ITEM_KEY;
> +	key.offset = (u64)-1;
> +
> +	root = btrfs_read_fs_root(fs_info, &key);
> +	if (IS_ERR(root)) {
> +		ret = PTR_ERR(root);
> +		errno = -ret;
> +		error("failed to get subvolume %llu: %m", rootid);
> +		return ret;
> +	}
> +	ipath = init_ipath(128 * BTRFS_PATH_NAME_MAX, root, &path);

128 is a magic constant, I've left it like that but we can use the
PATH_MAX and some named definition for the count.

> +	if (IS_ERR(ipath)) {
> +		ret = PTR_ERR(ipath);
> +		errno = -ret;
> +		error("failed to initialize ipath: %m");
> +		return ret;
> +	}
> +	ret = paths_from_inode(ino, ipath);
> +	if (ret < 0) {
> +		errno = -ret;
> +		error("failed to resolve root %llu ino %llu to paths: %m", rootid, ino);
> +		goto out;
> +	}
> +	for (int i = 0; i < ipath->fspath->elem_cnt; i++)
> +		printf("  (subvolume %llu)/%s\n", rootid, (char *)ipath->fspath->val[i]);
> +	if (ipath->fspath->elem_missed)
> +		printf("  (subvolume %llu) %d files not printed\n", rootid,
> +		       ipath->fspath->elem_missed);
> +out:
> +	free_ipath(ipath);
> +	return ret;
> +}
> +