On Wed, Jun 27, 2007 at 12:59:08AM +0530, Amit K. Arora wrote:

On Tue, Jun 26, 2007 at 12:14:00PM -0400, Andreas Dilger wrote:

quoted

On Jun 26, 2007  17:37 +0530, Amit K. Arora wrote:

quoted

quoted

I also thought another proposed flag was to determine whether mtime (and
maybe ctime) is changed when doing prealloc/dealloc space?  Default should
probably be to change mtime/ctime, and have FA_FL_NO_MTIME.  Someone else
should decide if we want to allow changing the file w/o changing ctime, if
that is required even though the file is not visibly changing.  Maybe the
ctime update should be implicit if the size or mtime are changing?

Is it really required ? I mean, why should we allow users not to update
ctime/mtime even if the file metadata/data gets updated ? It sounds
a bit "unnatural" to me.
Is there any application scenario in your mind, when you suggest of
giving this flexibility to userspace ?

One reason is that XFS does NOT update the mtime/ctime when doing the
XFS_IOC_* allocation ioctls.

Not totally correct.

XFS_IOC_ALLOCSP/FREESP change timestamps if they change
the file size (via the truncate call made to change the file size).
If they don't change the file size, then they are a no-op and should
not change the file size.

XFS_IOC_RESVSP/UNRESVSP don't change timestamps just like they don't
change file size. That is by design AFAICT so these calls can be
used by HSM-type applications that don't want to change timestamps
when punching out data blocks or preallocating new ones.

Hmm.. I personally will call it a bug in XFS code then. :)

No, I'd call it useful. :)

quoted

quoted

I think, modifying ctime/mtime should be dependent on the other flags.
E.g., if we do not zero out data blocks on allocation/deallocation,
update only ctime. Otherwise, update ctime and mtime both.

I'm only being the advocate for requirements David Chinner has put
forward due to existing behaviour in XFS.  This is one of the reasons
why I think the "flags" mechanism we now have - we can encode the
various different behaviours in any way we want and leave it to the
caller.

I understand. May be we can confirm once more with David Chinner if this
is really required. Will it really be a compatibility issue if new XFS
preallocations (ie. via fallocate) update mtime/ctime?

It should be left up to the filesystem to decide. Only the
filesystem knows whether something changed and the timestamp should
or should not be updated.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group