On Wed, Feb 13, 2013 at 04:40:35PM +0100, Bernd Schubert wrote: > >The general advise (even before this Bug) is that XFS should be used, > >which is not affected with this problem (yet?). > > Hmm, well, always depends on the workload. XFS won't suffer from this collision bug, for 2 reasons. The first is that XFS uses a virtual mapping for directory data and uses an encoded index into that virtual mapping as the cookie data. You can't have 2 entries at the same index, so you cannot get cookie collisions. The second is that the virtual mapping is for a 32GB data segment, (2^35 bytes) and, like so much of XFS, the cookie is made up of bitfields that encode a specific location. The high bits are the virtual block offset into the directory data segment, the low bits the offset into the directory block. Given that directory entries are aligned to 8 bytes, the offset into the directory block can have 3 bits compressed out and hence we end up with only 32 bits being needed to address the entire 32GB directory data segment. So, there are no collisions or 32/64 bit issues with XFS directory cookies regardless of the workload. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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
