On 10/24/12 19:47, Chris Mason wrote: > On Tue, Oct 23, 2012 at 03:53:13PM -0600, Dave Chinner wrote: >> On Tue, Oct 23, 2012 at 08:30:44AM -0400, Christoph Hellwig wrote: >>> On Thu, Oct 18, 2012 at 04:11:17PM +1100, Dave Chinner wrote: >>>> So, I was bored a few days ago, and I was sick of having to run >>>> xfs_db incorrectly report free space extents when the filesytem is >>>> mounted, so I decided to extend fiemap to export freespace mappings >>>> to userspace so I could get the information coherently through the >>>> mounted filesystem. >>>> >>>> Yes, this could probably be considered interface abuse but, well, it >>>> was simple to do because extent mapping is exactly what fiemap is >>>> designed to do. Hence I didn't have to write new walkers/formatters >>>> and I was using code I knew worked correctly. >>> I think the right way to handle this is to introduce a new ioctl which >>> uses the same structures. That way we have a reasonable interface, >>> without issue like which file does it need to be called on because the >>> VFS glue can turn it into a superblock op. >> A VFS level ioctl or an XFS ioctl? >> >> I thought about a new ioctl, but then what's the point of having an >> extensible fiemap interface if we create new ioctls with an >> identical interface for doing something that the existing ioctl is >> perfectly capable of doing? I'd still need special flags to control >> the ioctl behaviour even though it uses struct fiemap and plumbing, >> so it seemed pointless to introduce a new ioctl.... Hi Dave, I am writing XFS shrinkfs feature, and I really need an approach to get the free space of an XFS file system since xfs_db can not fetch agf->agf_freeblks and agf_btreeblks against a mounted partition to calculate it out for online shrink operation that just as what's you have mentioned above. So currently I add a new ioctl for this purpose, that's would be fine if we can have a fiemap interface to do it so that I can kill this new ioctl to avoid duplicate efforts. Thanks, -Jeff > This brings us one step close to the norton disk doctor defrag display. > I'm all for it in the main fiemap call, it makes much more sense for the > users I think. > > -chris > > _______________________________________________ > xfs mailing list > xfs@xxxxxxxxxxx > http://oss.sgi.com/mailman/listinfo/xfs -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
