On Apr 4, 2013, at 11:00 AM, Mitch Harder <mitch.harder@xxxxxxxxxxxxxxxx> wrote: > > I disagree with cwillu regarding the default setting for extended inode refs. > > While the extended inode refs are a great addition and solve a long > standing problem, it appears only the 3.9.0_rc kernel consistently > works with extended inode refs. And extended inode refs are related to leaf size, in a way that explains a default 4KB leaf size being mountable with older kernels, but volumes created with larger leaf sizes aren't mountable? Just a yes or no is fine, I probably wouldn't understand an explanation of the relationship. > > There should be at least a few working kernel versions out there > before this becomes the default. Options like this that will make > btrfs unmountable on older kernel versions need "buy-in" by the users. > > There is still the capability to enable extended inode refs with btrfstune. The behavior, in effect, acts as a change to the on disk format. It won't make sense to most users that default 4KB leaf sizes are backwards compatible with prior kernels, but 8/16/32KB leaf size is not. It's likely I don't know enough about kernel and fs development, but my instinct is that a longterm kernel needs to support a feature before the feature be a default. If the experimental fs card is applicable, I'd still say that this seems close enough to a format change that it should be postponed to a planned point in time when also implementing other features having a similar consequence. Otherwise, people can't regress to older kernels at all. And while the most common convention by far in btrfs troubleshooting is to go to a newer kernel, finding regressions either in btrfs let alone elsewhere (e.g. video card drivers) is rather significantly inhibited by being unable to mount a btrfs volume. The prospect of a (final release) Fedora 19 created btrfs volume being totally unreadable by anything less than kernel 3.9.0 is a bit eyebrow raising. Chris Murphy-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
