On Tue, Mar 29, 2016 at 02:28:28PM -0500, Eric Sandeen wrote:
> Today, a kernel which refuses to mount a filesystem read-write
> due to unknown ro-compat features can still transition to read-write
> via the remount path. The old kernel is most likely none the wiser,
> because it's unaware of the new feature, and isn't using it. However,
> writing to the filesystem may well corrupt metadata related to that
> new feature, and moving to a newer kernel which understand the feature
> will have problems.
>
> Right now the only ro-compat feature we have is the free inode btree,
> which showed up in v3.16. It would be good to push this back to
> all the active stable kernels, I think, so that if anyone is using
> newer mkfs (which enables the finobt feature) with older kernel
> releases, they'll be protected.
Ok, so the bug was introduced with the original extended feature
masks in commit e721f50 ("xfs: implement extended feature masks"),
which was introduced in 3.10. So it will need to go back to stable
kernels all the way back to 3.10, right?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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