Arnd Bergmann <arnd@xxxxxxxx> wrote: > > > For the volume id, I could not find any file system that requires more > > > than 32 bytes here, which is also reasonable to put into the structure. > > > Make it 36 if you want to cover ascii encoded UUIDs. > > > > You should also include a length. Volume IDs may be binary rather than > > NUL-terminated strings. > > Yes, maybe. There are several possible encodings for this. I was actually > thinking of fixed-length string rather than zero-terminated, but that > is possible as well. If this gets added, we need to audit every possible > use to make sure each of them is covered. My point was mostly that if we > need at most 40 bytes, it doesn't have to be variable length at all. I suppose it depends what you want it for. Steve French asked for it: > (4) Should the inode number and data version number fields be > 128-bit? > This is tricky for SMB2, if you can also provide a device id (or an object id of some sort for the superblock) then 64 bit inode number is ok. But I'm not sure what he wants to put in there. He didn't respond to my reply: A remote device ID? That would be possible. That could be used by AFS to return the numeric volume ID (32 bits) and by NFS to return the FSID (128 bits). Would you be using the VolumeGUID (128 bits) for SMB2? so I'm not sure what he's thinking of. Looking through various filesystems: FS SOURCE FORMAT LENGTH (BYTES) ======= =============================== ======= ============= - __kernel_fsid_t int 8 - super_block::s_id chars 32 ext234 superblock s_uuid UUID 16 ext234 superblock s_volume_name chars 16 nfs2 FSID int 4 nfs3 FSID int 8 nfs4 FSID int 16 afs Volume Name + type chars 64+1 afs Numeric volume ID int 4 cifs VolumeGUID UUID 16 btrfs superblock fsid bytes 16 fat superblock system_id+version? bytes 8+2 ntfs volume_serial_number int 8 ntfs FILE_Volume object_id UUID 16 xfs superblock sb_fname chars 12 xfs superblock sb_uuid UUID 16 jfs superblock s_uuid UUID 16 jfs superblock s_label bytes 16 isofs medium_catalog_number chars 13 isofs volume_id chars 32 udf volIdent chars 32 it would seem that a 16-byte (128-bit) ID would suit quite well. That would be able to contain most things and could be added to the super_block struct. That would also give NFSD something to use as a default FSID and Samba something to used as a VolumeGUID. David -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
