Re: explicit dcache <-> user-space cache coherency, sys_mark_dir_clean(), O_CLEAN

Ingo Molnar
2004-02-21T17:45:36Z

* viro@parcelfarce.linux.theplanet.co.uk <viro@parcelfarce.linux.theplanet.co.uk> wrote:

> On Sat, Feb 21, 2004 at 08:58:53AM +0100, Ingo Molnar wrote:
> > filesystems that dont have 64-bit, monotonic timestamps will return
> > -ENOSYS. This should include even XFS at the moment, because the
> > timestamp is not guaranteed to be monotonic.
>
> > any other problems with this concept?
>
> If we are demanding specific filesystems, we could simply say "use JFS
> in case-insensitive mode" and be done with that. Which deals with all
> problems, since fs code will guarantee uniqueness, etc.

what i propose is a pretty generic feature that we need anyway (current
32-bit, 1-sec granular mtime in most filesystems is already problematic
for things like make dependencies), while "use JFS in case-insensitive
mode" is to degrade a filesystem to a non-POSIX mode. I dont think the
two approaches are equivalent. Having good, monotonic, finegrained
timestamps is a thing of the future - case-insensitive lowlevel
filesystems are a thing of the past.

Ingo