On Feb 2, 2021, at 10:36, Theodore Ts'o <tytso@xxxxxxx> wrote: > > I've released e2fsprogs 1.46.0 in all of the usual places; > > E2fsprogs now supports file systems which have both file system > encryption and the casefold feature enabled. This requires Linux > version 5.10. Gah! I just noticed these patches being submitted to the kernel, but they break the dirdata format in an incompatible manner. I hadn't been paying close attention to casefold + encryption since I thought it was only changing the hashing function and not the actual dirent format, and I didn't see these patches to e2fsprogs being submitted to the list (I couldn't find them in patchworks either). Since this hasn't been landed to the kernel yet, and 1.46.0 was *just* released, can we roll this back and instead make the extra hash stored in a dirdata field? Preferably #3, since #1 is the Lustre FID, and #2 was proposed for the high 32 bits of the 64-bit inode number (though it was never landed and I don't think it is in use anywhere). Having just looked at these patches for the first time, I can't say for sure, but it looks like only a small on-disk format change would be needed to make both features compatible with each other. There would need to be a bit set in the dirent type field to indicate that there is a hash stored after the name: #define EXT2_DIRENT_HASH 0x40 and the length of the hash field would be stored as the first byte. Since the hash is stored aligned on a 4-byte boundary, the length is variable (8+alignment), but storing the length at the start would not add any more space for 3/4 of the names due to the existing padding for alignment. Cheers, Andreas
