On 06/29/2011 01:10 PM, Sunil Mushran wrote: > On 06/29/2011 12:40 AM, Christoph Hellwig wrote: >> On Wed, Jun 29, 2011 at 04:53:07PM +1000, Dave Chinner wrote: >>> On Tue, Jun 28, 2011 at 11:33:19AM -0400, Josef Bacik wrote: >>>> This is a test to make sure seek_data/seek_hole is acting like it >>>> does on >>>> Solaris. It will check to see if the fs supports finding a hole or >>>> not and will >>>> adjust as necessary. >>> So I just looked at this with an eye to validating an XFS >>> implementation, and I came up with this list of stuff that the test >>> does not cover that I'd need to test in some way: >>> >>> - files with clean unwritten extents. Are they a hole or >>> data? What's SEEK_DATA supposed to return on layout like >>> hole-unwritten-data? i.e. needs to add fallocate to the >>> picture... >>> >>> - files with dirty unwritten extents (i.e. dirty in memory, >>> not on disk). They are most definitely data, and most >>> filesystems will need a separate lookup path to detect >>> dirty unwritten ranges because the state is kept >>> separately (page cache vs extent cache). Plenty of scope >>> for filesystem specific bugs here so needs a roubust test. >> The discussion leading up to the resurrection of SEEK_HOLE/SEEK_DATA >> was pretty much about that point. The conclusion based on the Sun >> documentation and common sense was that SEEK_DATA may only consider >> unwritten extents as hole if the filesystem has a way to distinguish >> plain unwritten extents and those that have been dirtied. Else it >> should be considered data. >> >> Testing for making sure dirty preallocated areas aren't wrongly >> reported sounds relatively easy, the rest falls into implementation >> details, which imho is fine. Not reporting preallocated extents >> as holes just is a quality of implementation issue and not a bug. > > I agree. And if I might add my 2 cents that it would be much easier > if we added another test that created files with all the worrisome boundary > conditions and used SEEK_DATA/HOLE to copy the files and compared > using md5sum. This would be far easier than one that expects a certain > pos for each operation. That's a great point, I think I will rig something like that up. Thanks, Josef -- 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
