Re: [f2fs-dev] [PATCH v4 2/3] f2fs: include charset encoding information in the superblock

[Chao Yu <chao@kernel.org>]

On 2019-7-24 7:05, Daniel Rosenberg via Linux-f2fs-devel wrote:
> Add charset encoding to f2fs to support casefolding. It is modeled after
> the same feature introduced in commit c83ad55eaa91 ("ext4: include charset
> encoding information in the superblock")
> 
> Currently this is not compatible with encryption, similar to the current
> ext4 imlpementation. This will change in the future.
> 
> From the ext4 patch:
> """
> The s_encoding field stores a magic number indicating the encoding
> format and version used globally by file and directory names in the
> filesystem.  The s_encoding_flags defines policies for using the charset
> encoding, like how to handle invalid sequences.  The magic number is
> mapped to the exact charset table, but the mapping is specific to ext4.
> Since we don't have any commitment to support old encodings, the only
> encoding I am supporting right now is utf8-12.1.0.
> 
> The current implementation prevents the user from enabling encoding and
> per-directory encryption on the same filesystem at the same time.  The
> incompatibility between these features lies in how we do efficient
> directory searches when we cannot be sure the encryption of the user
> provided fname will match the actual hash stored in the disk without
> decrypting every directory entry, because of normalization cases.  My
> quickest solution is to simply block the concurrent use of these
> features for now, and enable it later, once we have a better solution.
> """
> 
> Signed-off-by: Daniel Rosenberg <drosen@google.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,