Btrfs RAID 5/6 Sub-Page Support Readied For Linux 5.19
The Btrfs "Subpage" functionality is for handling sector sizes that are smaller than the page size, rather than traditionally the two sizes needing to be the same.
Btrfs has a lot of code around its sub-page support and needed special handling for RAID5/RAID6. That code has been under review and appears poised for introduction in Linux 5.19.
As of this past week the RAID5/6 sub-page support is ready and enabled within kdave's for-next branch ahead of the Linux 5.19 merge window opening later this month.
Enabling the RAID5/RAID6 sub-page support for Btrfs was carried out by SUSE's Qu Wenruo.
More broadly, the current state and information around Btrfs' native RAID support can be found via the Btrfs Wiki. Specifically there is also the RAID 5/6 page that does still carry the warning, "The parity RAID code has a specific issue with regard to data integrity. It should not be used for metadata. For data, it should be safe as long as a scrub is run immediately after any unclean shutdown."
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