On Tue, Mar 13, 2012 at 04:22:52PM -0400, Phillip Susi wrote: > > I think a format change would be preferable to runtime sorting. Are you volunteering to spearhead the design and coding of such a thing? Run-time sorting is backwards compatible, and a heck of a lot easier to code and test... The reality is we'd probably want to implement run-time sorting *anyway*, for the vast majority of people who don't want to convert to a new incompatible file system format. (Even if you can do the conversion using e2fsck --- which is possible, but it would be even more code to write --- system administrators tend to be very conservative about such things, since they might need to boot an older kernel, or use a rescue CD that doesn't have an uptodate kernel or file system utilities, etc.) > So the index nodes contain the hash ranges for the leaf block, but > the leaf block only contains the regular directory entries, not a > hash for each name? That would mean that adding or removing names > would require moving around the regular directory entries wouldn't > it? They aren't sorted in the leaf block, so we only need to move around regular directory entries when we do a node split (and at the moment we don't support shrinking directories), so we don't have to worry the reverse case. > I would think that hash collisions are rare enough that reading a > directory block you end up not needing once in a blue moon would be > chalked up under "who cares". So just stick with hash, offset pairs > to map the hash to the normal directory entry. With a 64-bit hash, and if we were actually going to implement this as a new incompatible feature, you're probably right in terms of accepting the extra directory block search. We would still have to implement the case where hash collisions *do* exist, though, and make sure the right thing happens in that case. Even if the chance of that happening is 1 in 2**32, with enough deployed systems (i.e., every Android handset, etc.) it's going to happen in real life. - Ted -- 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
