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: > > On Jun 26, 2007 17:37 +0530, Amit K. Arora wrote: > > > > 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. :) > > > 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 - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
