On 2016-08-22 04:21, Andriy Gapon wrote: > On 01/08/2016 22:37, Allan Jude wrote: >> Author: allanjude >> Date: Mon Aug 1 19:37:43 2016 >> New Revision: 303630 >> URL: https://svnweb.freebsd.org/changeset/base/303630 >> >> Log: >> Make boot code and loader check for unsupported ZFS feature flags >> >> OpenZFS uses feature flags instead of a zpool version number to track >> features since the split from Oracle. In addition to avoiding confusion >> on ZFS vs OpenZFS version numbers, this also allows features to be added >> to different operating systems that use OpenZFS in different order. >> >> The previous zfs boot code (gptzfsboot) and loader (zfsloader) blindly >> tries to read the pool, and if failed provided only a vague error message. >> >> With this change, both the boot code and loader check the MOS features >> list in the ZFS label and compare it against the list of features that >> the loader supports. If any unsupported feature is active, the pool is >> not considered as a candidate for booting, and a helpful diagnostic >> message is printed to the screen. Features that are merely enabled via >> zpool upgrade, but not in use, do not block booting from the pool. >> >> Submitted by: Toomas Soome <tso...@me.com> >> Reviewed by: delphij, mav >> Relnotes: yes >> Differential Revision: https://reviews.freebsd.org/D6857 > > It is really great to get a helpful diagnostic message when an unsupported > feature is seen. Thank you for that! > > But I would prefer that the check is done on a filesystem level, not on a pool > level. That is, I would like to be able to enable features that are not > supported by ZFS boot chain on a boot pool as long as I do not enable such > features on a boot filesystem. E.g., the large blocks support could be one of > such features.
This was my though originally, but it is not as easy to tell if a filesystem has ever used a feature. For pool wide, it is just a property. Do you know of an easy way to get this information for a specific file system? > > And, as I've said in another email, I really do not think that we should > strive > to support all possible (non-essential) ZFS features in the ZFS boot chain. > -- Allan Jude
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