On Tue, 2009-10-20 at 18:44 -0600, Andreas Dilger wrote: > On 20-Oct-09, at 14:49, Steve French wrote: > > On Tue, Oct 20, 2009 at 3:33 PM, Andreas Dilger <adilger@xxxxxxx> > > wrote: > >> For those users/admins that want to be able to change this (due to > >> Samba, or whatever), great, we can give them this ability, but for > >> users who do NOT want regular users to be able to change the file > >> creation timestamp, that should be possible as well. > > > > So, are we ready for Mingming or one of the ext4 developers to propose > > a patch for this via xattrs (I can do a similar one for cifs). > > Sounds like various have said: > > > > 1) xattrs instead of ioctl > > 2) get of create time allowed by default, but set of create time > > limited > > > A wildly untested/uncompiled patch is attached for purposes of > discussion. > One issue that I've already come across is if we are storing a raw > "timespec" > we will get different xattrs on disk in the fallback case where the on- > disk > inodes are not large enough to store the crtime inside the inode. > > This version of the patch will fall back to storing the timespec on disk > in the supplied size/endianness as an xattr, but it definitely needs > to be > handled more appropriately (endian/word size). It _would_ be nice to > store > a full 64-bit timespec on disk, but given that the in-inode format > only can > handle 34 bits of seconds + 30 bits of nanoseconds, it isn't clear > whether > the "fallback" should do better than that. > Could we transparently convert user provided raw creation time and store the same format as whose in-inode creation timestamp in the fallback case? Just to be consistent. User doesn't have to know what type/size of ext4 inode it is accessing... > The main question is whether storing a "user.crtime" as an on-disk xattr > is a desirable fallback, or if this should just fail? I think it would be nice to have this fallback, just be consistent, that for all type of ext4 inodes there is a way to set file creation time for allowed users(whether default 256 bytes large inode which could store the 34+30bit creation time, or the 128 bytes smaller inode, which doesn't have space to store the creation in the inode) Regards, Mingming > Similarly, should > the lack of on-disk crtime return "0.0" as the creation time, or should > it return -ENODATA or similar? > Cheers, Andreas > -- > Andreas Dilger > Sr. Staff Engineer, Lustre Group > Sun Microsystems of Canada, Inc. -- 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
