Re: [PATCH 3/4] btrfs: introduce new "rescue=ignoremetacsums" mount option

[David Sterba <dsterba@suse.cz>]

On Tue, Jun 11, 2024 at 02:51:37PM +0930, Qu Wenruo wrote:
> This patch introduces "rescue=ignoremetacsums" to ignore metadata csums,
> meanwhile all the other metadata sanity checks are still kept as is.
> 
> This new mount option is mostly to allow the kernel to mount an
> interrupted checksum conversion (at the metadata csum overwrite stage).
> 
> And since the main part of metadata sanity checks is inside
> tree-checker, we shouldn't lose much safety, and the new mount option is
> rescue mount option it requires full read-only mount.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>

> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -367,6 +367,7 @@ int btrfs_validate_extent_buffer(struct extent_buffer *eb,
>  	u8 result[BTRFS_CSUM_SIZE];
>  	const u8 *header_csum;
>  	int ret = 0;
> +	bool ignore_csum = btrfs_test_opt(fs_info, IGNOREMETACSUMS);

const

> --- a/fs/btrfs/messages.c
> +++ b/fs/btrfs/messages.c
> @@ -20,7 +20,7 @@ static const char fs_state_chars[] = {
>  	[BTRFS_FS_STATE_TRANS_ABORTED]		= 'A',
>  	[BTRFS_FS_STATE_DEV_REPLACING]		= 'R',
>  	[BTRFS_FS_STATE_DUMMY_FS_INFO]		= 0,
> -	[BTRFS_FS_STATE_NO_CSUMS]		= 'C',
> +	[BTRFS_FS_STATE_NO_DATA_CSUMS]		= 'C',

There should be the status also when the metadata checksums are not
validated, the letters are arbitrary but should reflect the state if
possible, I'd suggest to use 'S' here.

What I'm missing is the sysfs.c update, all options supported by rescue
need to be listed in rescue_opts.