Pull btrfs updates from David Sterba:
 "We have a mix of all kinds of changes, feature updates, core stuff,
  performance improvements and lots of cleanups and preparatory changes.

  User visible:

   - export filesystem generation in sysfs

   - new features for mount option 'rescue':
       - what's currently supported is exported in sysfs
       - 'ignorebadroots'/'ibadroots' - continue even if some essential
         tree roots are not usable (extent, uuid, data reloc, device,
         csum, free space)
       - 'ignoredatacsums'/'idatacsums' - skip checksum verification on
         data
       - 'all' - now enables 'ignorebadroots' + 'ignoredatacsums' +
         'nologreplay'

   - export read mirror policy settings to sysfs, new policies will be
     added in the future

   - remove inode number cache feature (mount -o inode_cache), obsoleted
     in 5.9

  User visible fixes:

   - async discard scheduling fixes on high loads

   - update inode byte counter atomically so stat() does not report
     wrong value in some cases

   - free space tree fixes:
       - correctly report status of v2 after remount
       - clear v1 cache inodes when v2 is newly enabled after remount

  Core:

   - switch own tree lock implementation to standard rw semaphore:
       - one-level lock nesting is not required anymore, the last use of
         this was in free space that's now loaded asynchronously
       - own implementation of adaptive spinning before taking mutex has
         been part of rwsem
       - performance seems to be better in general, much better (+tens
         of percents) for some workloads
       - lockdep does not complain

   - finish direct IO conversion to iomap infrastructure, remove
     temporary workaround for DSYNC after iomap API updates

   - preparatory work to support data and metadata blocks smaller than
     page:
       - generalize code that assumes sectorsize == PAGE_SIZE, lots of
         refactoring
       - planned namely for 64K pages (eg. arm64, ppc64)
       - scrub read-only support

   - preparatory work for zoned allocation mode (SMR/ZBC/ZNS friendly):
       - disable incompatible features
       - round-robin superblock write

   - free space cache (v1) is loaded asynchronously, remove tree path
     recursion

   - slightly improved time tacking for transaction kthread wake ups

  Performance improvements (note that the numbers depend on load type or
  other features and weren't run on the same machine):

   - skip unnecessary work:
       - do not start readahead for csum tree when scrubbing non-data
         block groups
       - do not start and wait for delalloc on snapshot roots on
         transaction commit
       - fix race when defragmenting leads to unnecessary IO

   - dbench speedups (+throughput%/-max latency%):
       - skip unnecessary searches for xattrs when logging an inode
         (+10.8/-8.2)
       - stop incrementing log batch when joining log transaction (1-2)
       - unlock path before checking if extent is shared during nocow
         writeback (+5.0/-20.5), on fio load +9.7% throughput/-9.8%
         runtime
       - several tree log improvements, eg. removing unnecessary
         operations, fixing races that lead to additional work
         (+12.7/-8.2)

   - tree-checker error branches annotated with unlikely() (+3%
     throughput)

  Other:

   - cleanups

   - lockdep fixes

   - more btrfs_inode conversions

   - error variable cleanups"

* tag 'for-5.11-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (198 commits)
  btrfs: scrub: allow scrub to work with subpage sectorsize
  btrfs: scrub: support subpage data scrub
  btrfs: scrub: support subpage tree block scrub
  btrfs: scrub: always allocate one full page for one sector for RAID56
  btrfs: scrub: reduce width of extent_len/stripe_len from 64 to 32 bits
  btrfs: refactor btrfs_lookup_bio_sums to handle out-of-order bvecs
  btrfs: remove btrfs_find_ordered_sum call from btrfs_lookup_bio_sums
  btrfs: handle sectorsize < PAGE_SIZE case for extent buffer accessors
  btrfs: update num_extent_pages to support subpage sized extent buffer
  btrfs: don't allow tree block to cross page boundary for subpage support
  btrfs: calculate inline extent buffer page size based on page size
  btrfs: factor out btree page submission code to a helper
  btrfs: make btrfs_verify_data_csum follow sector size
  btrfs: pass bio_offset to check_data_csum() directly
  btrfs: rename bio_offset of extent_submit_bio_start_t to dio_file_offset
  btrfs: fix lockdep warning when creating free space tree
  btrfs: skip space_cache v1 setup when not using it
  btrfs: remove free space items when disabling space cache v1
  btrfs: warn when remount will not change the free space tree
  btrfs: use superblock state to print space_cache mount option
  ...