Re: [PATCH v2 12/17] btrfs: turn on inlinecrypt mount option for encrypt

["Luís Henriques" <lhenriques@suse.de>]

Sweet Tea Dorminy <sweettea-kernel@dorminy.me> writes:

> fscrypt's extent encryption requires the use of inline encryption or the
> software fallback that the block layer provides; it is rather
> complicated to allow software encryption with extent encryption due to
> the timing of memory allocations. Thus, if btrfs has ever had a
> encrypted file, or when encryption is enabled on a directory, update the
> mount flags to include inlinecrypt.
>
> Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
> ---
>  fs/btrfs/ioctl.c |  4 ++++
>  fs/btrfs/super.c | 10 ++++++++++
>  2 files changed, 14 insertions(+)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 91ad59519900..11866a88e33f 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4574,6 +4574,10 @@ long btrfs_ioctl(struct file *file, unsigned int
>  		 * state persists.
>  		 */
>  		btrfs_set_fs_incompat(fs_info, ENCRYPT);
> +		if (!(inode->i_sb->s_flags & SB_INLINECRYPT)) {
> +			inode->i_sb->s_flags |= SB_INLINECRYPT;
> +			mb();

I've no idea this mb() is needed here, but I know it's usually a good
practice to document why it is needed.

Cheers,
-- 
Luís

> +		}
>  		return fscrypt_ioctl_set_policy(file, (const void __user *)arg);
>  	}
>  	case FS_IOC_GET_ENCRYPTION_POLICY:
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 0cc9c2909f64..1e9a93c6750a 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -1165,6 +1165,16 @@ static int btrfs_fill_super(struct super_block *sb,
>  		return err;
>  	}
>  
> +	if (btrfs_fs_incompat(fs_info, ENCRYPT)) {
> +		if (IS_ENABLED(CONFIG_FS_ENCRYPTION_INLINE_CRYPT)) {
> +			sb->s_flags |= SB_INLINECRYPT;
> +		} else {
> +			btrfs_err(fs_info, "encryption not supported");
> +			err = -EINVAL;
> +			goto fail_close;
> +		}
> +	}
> +
>  	inode = btrfs_iget(sb, BTRFS_FIRST_FREE_OBJECTID, fs_info->fs_root);
>  	if (IS_ERR(inode)) {
>  		err = PTR_ERR(inode);
> -- 
>
> 2.40.1
>