* Dave Chinner:

IOWs, what Linux really needs is a listxattr2() syscall that works
the same way that getdents/XFS_IOC_ATTRLIST_BY_HANDLE work. With the
list function returning value sizes and being able to iterate
effectively, every problem that listxattr() causes goes away.

getdents has issues of its own because it's unspecified what happens if
the list of entries is modified during iteration.  Few file systems add
another tree just to guarantee stable iteration.

Maybe that's different for xattrs because they are supposed to be small
and can just be snapshotted with a full copy?

Thanks,
Florian