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Re: [PATCH 1/6] xstat: Add a pair of system calls to make extended file stats available
- From: David Howells <dhowells at redhat dot com>
- To: Andreas Dilger <adilger at dilger dot ca>
- Cc: dhowells at redhat dot com, linux-fsdevel at vger dot kernel dot org, linux-nfs at vger dot kernel dot org, linux-cifs at vger dot kernel dot org, samba-technical at lists dot samba dot org, linux-ext4 at vger dot kernel dot org, wine-devel at winehq dot org, kfm-devel at kde dot org, nautilus-list at gnome dot org, linux-api at vger dot kernel dot org, libc-alpha at sourceware dot org
- Date: Thu, 26 Apr 2012 14:32:36 +0100
- Subject: Re: [PATCH 1/6] xstat: Add a pair of system calls to make extended file stats available
- References: <5D4BF4AB-47E9-4E25-B2A3-F895C98BDAA3@dilger.ca> <20120419140558.17272.74360.stgit@warthog.procyon.org.uk> <20120419140612.17272.57774.stgit@warthog.procyon.org.uk>
Andreas Dilger <adilger@dilger.ca> wrote:
> > 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.
> > 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