From: David Howells Subject: Re: [PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6] Date: Thu, 22 Jul 2010 13:25:31 +0100 Message-ID: <30638.1279801531@redhat.com> References: <20100715021709.5544.64506.stgit@warthog.procyon.org.uk> <20100715021712.5544.44845.stgit@warthog.procyon.org.uk> <20100718084824.GA27794@infradead.org> Cc: dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Christoph Hellwig , viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, samba-technical-w/Ol4Ecudpl8XjKLYN78aQ@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, drepper-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org To: Jan Engelhardt Return-path: In-Reply-To: Sender: linux-cifs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org Jan Engelhardt wrote: > >> (8) Allow the filesystem to indicate what it can/cannot provide: A > >> filesystem can now say it doesn't support a standard stat feature if > >> that isn't available. > > > >What for? > > Given xstat.otime=0, how would you determine whether the file is really > tagged with a date of 1970, or whether it's just the fs which didnot > store this kind of information. I was thinking more of stuff that's already in the Linux stat struct, some of which is fabricated because the underlying fs doesn't support it. Take RomFS for example: it fabricates all of st_mtime, st_atime, st_ctime, st_nlinks, st_blocks, st_uid and st_gid because none of them are stored in the medium Similarly, UbiFS fabricates st_blocks and complains in a comment that it makes no sense for that type of filesystem. There are other examples. David