Recalling the first round of new code for 5.10, in which we added: - New feature: Widen inode timestamps and quota grace expiration timestamps to support dates through the year 2486. - New feature: storing inode btree counts in the AGI to speed up certain mount time per-AG block reservation operatoins and add a little more metadata redundancy. For the second round of new code for 5.10: - Deprecate the V4 filesystem format, some disused mount options, and some legacy sysctl knobs now that we can support dates into the 25th century. Note that removal of V4 support will not happen until the early 2030s. - Fix some probles with inode realtime flag propagation. - Fix some buffer handling issues when growing a rt filesystem. - Fix a problem where a BMAP_REMAP unmap call would free rt extents even though the purpose of BMAP_REMAP is to avoid freeing the blocks. - Strengthen the dabtree online scrubber to check hash values on child dabtree blocks. - Actually log new intent items created as part of recovering log intent items. - Fix a bug where quotas weren't attached to an inode undergoing bmap intent item recovery. - Fix a buffer overrun problem with specially crafted log buffer headers. - Various cleanups to type usage and slightly inaccurate comments. - More cleanups to the xattr, log, and quota code. - Don't run the (slower) shared-rmap operations on attr fork mappings. - Fix a bug where we failed to check the LSN of finobt blocks during replay and could therefore overwrite newer data with older data. - Clean up the ugly nested transaction mess that log recovery uses to stage intent item recovery in the correct order by creating a proper data structure to capture recovered chains. - Use the capture structure to resume intent item chains with the same log space and block reservations as when they were captured. - Fix a UAF bug in bmap intent item recovery where we failed to maintain our reference to the incore inode if the bmap operation needed to relog itself to continue. - Rearrange the defer ops mechanism to finish newly created subtasks of a parent task before moving on to the next parent task. - Automatically relog intent items in deferred ops chains if doing so would help us avoid pinning the log tail. This will help fix some log scaling problems now and will facilitate atomic file updates later. - Fix a deadlock in the GETFSMAP implementation by using an internal memory buffer to reduce indirect calls and copies to userspace, thereby improving its performance by ~20%. - Fix various problems when calling growfs on a realtime volume would not fully update the filesystem metadata. - Fix broken Kconfig asking about deprecated XFS when XFS is disabled.