Re: [PATCH] btrfs: copy fsid to super_block s_uuid

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Aug 01, 2017 at 06:35:08PM +0800, Anand Jain wrote:
> We didn't copy fsid to struct super_block.s_uuid so Overlay disables
> index feature with btrfs as the lower FS.
> 
> kernel: overlayfs: fs on '/lower' does not support file handles, falling back to index=off.
> 
> Fix this by publishing the fsid through struct super_block.s_uuid.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
> I tried to know if in case did we deliberately missed this for some reason,
> however there is no information on that. If we mount a non-default subvol in
> the next mount/remount, its still the same FS, so publishing the FSID
> instead of subvol uuid is correct, OR I can't think any other reason for
> not using s_uuid for btrfs.
> 
> 
>  fs/btrfs/disk-io.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 080e2ebb8aa0..b7e72d040442 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -2899,6 +2899,7 @@ int open_ctree(struct super_block *sb,
>  
>  	sb->s_blocksize = sectorsize;
>  	sb->s_blocksize_bits = blksize_bits(sectorsize);
> +	memcpy(&sb->s_uuid, fs_info->fsid, BTRFS_FSID_SIZE);

uuid_copy()?

--D

>  
>  	mutex_lock(&fs_info->chunk_mutex);
>  	ret = btrfs_read_sys_array(fs_info);
> -- 
> 2.13.1
> 
> --
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