Re: [RFC PATCH 1/4] fs: Add FS_XFLAG_COMPRESSED & FS_XFLAG_ENCRYPTED for FS_IOC_FS[GS]ETXATTR API

[Eric Biggers]

On Sun, Feb 16, 2025 at 05:40:26PM +0100, Pali Rohár wrote:
> This allows to get or set FS_COMPR_FL and FS_ENCRYPT_FL bits via FS_IOC_FSGETXATTR/FS_IOC_FSSETXATTR API.
> 
> Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>

Does this really allow setting FS_ENCRYPT_FL via FS_IOC_FSSETXATTR, and how does
this interact with the existing fscrypt support in ext4, f2fs, ubifs, and ceph
which use that flag?  In the fscrypt case it's very intentional that
FS_ENCRYPT_FL can be gotten via FS_IOC_GETFLAGS but not set via FS_IOC_SETFLAGS.
A simple toggle of the flag can't work, as it doesn't provide the needed
information.  Instead there is a separate ioctl (FS_IOC_SET_ENCRYPTION_POLICY)
for enabling encryption which takes additional parameters and only works on
empty directories.

- Eric