Re: [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field

NeilBrown
2022-09-09T01:08:10Z

On Fri, 09 Sep 2022, NeilBrown wrote:
> On Fri, 09 Sep 2022, Trond Myklebust wrote:
>
> >
> > IOW: the minimal condition needs to be that for all cases below, the
> > application reads 'state B' as having occurred if any data was
> > committed to disk before the crash.
> >
> > Application Filesystem
> > =========== =========
> > read change attr <- 'state A'
> > read data <- 'state A'
> > write data -> 'state B'
> > <crash>+<reboot>
> > read change attr <- 'state B'
>
> The important thing here is to not see 'state A'. Seeing 'state C'
> should be acceptable. Worst case we could merge in wall-clock time of
> system boot, but the filesystem should be able to be more helpful than
> that.
>

Actually, without the crash+reboot it would still be acceptable to see
"state A" at the end there - but preferably not for long.
From the NFS perspective, the changeid needs to update by the time of a
close or unlock (so it is visible to open or lock), but before that it
is just best-effort.

NeilBrown