Re: [PATCH V1 3/9] fs/ext4: Disallow encryption if inode is DAX

Jan Kara
2020-05-14T10:23:51Z

On Wed 13-05-20 23:53:09, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> Encryption and DAX are incompatible. Changing the DAX mode due to a
> change in Encryption mode is wrong without a corresponding
> address_space_operations update.
>
> Make the 2 options mutually exclusive by returning an error if DAX was
> set first.
>
> Furthermore, clarify the documentation of the exclusivity and how that
> will work.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

>
> ---
> Changes:
> remove WARN_ON_ONCE
> Add documentation to the encrypt doc WRT DAX
> ---
> Documentation/filesystems/fscrypt.rst | 4 +++-
> fs/ext4/super.c | 10 +---------
> 2 files changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
> index aa072112cfff..1475b8d52fef 100644
> --- a/Documentation/filesystems/fscrypt.rst
> +++ b/Documentation/filesystems/fscrypt.rst
> @@ -1038,7 +1038,9 @@ astute users may notice some differences in behavior:
> - The ext4 filesystem does not support data journaling with encrypted
> regular files. It will fall back to ordered data mode instead.
>
> -- DAX (Direct Access) is not supported on encrypted files.
> +- DAX (Direct Access) is not supported on encrypted files. Attempts to enable
> + DAX on an encrypted file will fail. Mount options will _not_ enable DAX on
> + encrypted files.
>
> - The st_size of an encrypted symlink will not necessarily give the
> length of the symlink target as required by POSIX. It will actually
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index bf5fcb477f66..9873ab27e3fa 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1320,7 +1320,7 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
> if (inode->i_ino == EXT4_ROOT_INO)
> return -EPERM;
>
> - if (WARN_ON_ONCE(IS_DAX(inode) && i_size_read(inode)))
> + if (IS_DAX(inode))
> return -EINVAL;
>
> res = ext4_convert_inline_data(inode);
> @@ -1344,10 +1344,6 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
> ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
> ext4_clear_inode_state(inode,
> EXT4_STATE_MAY_INLINE_DATA);
> - /*
> - * Update inode->i_flags - S_ENCRYPTED will be enabled,
> - * S_DAX may be disabled
> - */
> ext4_set_inode_flags(inode);
> }
> return res;
> @@ -1371,10 +1367,6 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
> ctx, len, 0);
> if (!res) {
> ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
> - /*
> - * Update inode->i_flags - S_ENCRYPTED will be enabled,
> - * S_DAX may be disabled
> - */
> ext4_set_inode_flags(inode);
> res = ext4_mark_inode_dirty(handle, inode);
> if (res)
> --
> 2.25.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR