Re: [PATCH 1/6] xstat: Add a pair of system calls to make extended file stats available

Andreas Dilger [off-list ref] wrote:

quoted

The idea was initially proposed as a set of xattrs that could be
retrieved with getxattr(), but the general preferance proved to be
for new syscalls with an extended stat structure.

I would comment that it was the opposite.  It was originally a
stat()-like extension that degraded into a messy getxattr() mess.

Ummm...  No, my first attempt was definitely through getxattr().  You even
commented on it.

quoted

The fields in struct xstat come in a number of classes:

(0) st_dev, st_blksize, st_information.

    These are local data and are always available.

For the extra two bits it would cost us, I don't think st_blksize
and st_information should always be returned.

Fair enough.

st_blksize may be variable for a distributed filesystem,

I wonder if there's a way to make this explicit - or is it something that if
the bit isn't set, you can't use the value in st_blksize.  I wonder if this
value always has to be non-zero to make sure existing stat() doesn't explode.

and some of the fields in st_information (offline) may not be free to access
either.

True.

David