On Wed, Oct 08, 2008 at 10:04:40PM +0800, Tao Ma wrote: > > > Christoph Hellwig wrote: > > On Wed, Oct 08, 2008 at 09:56:41AM +0800, Tiger Yang wrote: > >> I have looked the patch for btrfs about this. We are different. > >> Btrfs store the whole xattr name including the prefix "user." > >> "trusted.", we store index number instead of it. > > > > I looked at the git tree and there are two users of > > ocfs2_xattr_handler(). > > > > (1) for using the ->list handler in listattr. That's something I fixed > > in btrfs that I wanted to point you to. The whole concept of a > > ->list handler is stupid, and it was only added as a hack for > > the tmpfs "generic" xattr support which is a mess. Instead of > > looking up a handler that would only do the same thing anyway > > for all on-disk attributes just call the code directly and > > have a map from index to prefix (look at > > fs/xfs/linux-2.6/xfs_xattr.c for an example). You > > also have a check for OCFS2_MOUNT_NOUSERXATTR for the user > > attributes, but that's much easier done by just checking the > > index in an if (and I'd personally just kill it completely, the > > options doesn't seem useful - but that's an unrelated bit) > yes, you are right. The handler for list is borrowed from ext3 and > somewhat ugly. We just need the prefix name but use such a complicated > method. Just a map from index to prefix should work fine. > > > > (2) For generating the hash. I don't quite understand why you want to > > also hash the prefix if it's not store on disk anyway but sorted > > into the numeric buckets. > This is done intentionally. See the design doc > http://oss.oracle.com/osswiki/OCFS2/DesignDocs/ExtendedAttributes. > "Each entry has a 32-bit hash value associated with it. The hash value > is calculated using the full (prefix.suffix) name of the xattr to avoid > hash collisions when the same suffix is used in multiple attribute > namespaces. " > So Mark, do you think we need this prefix hash? > Anyway, if we make consensus that the hash calculation doesn't need > prefix any more, we can remove the ocfs2_xattr_handler safely. Removing the prefix hash should be fine. Technically, this changes the disk format, but nobody should be using this for production yet anyway. --Mark -- Mark Fasheh -- 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
