Pull f2fs updates from Jaegeuk Kim:
 "In this round, we've focused on bug fixes since Pixel devices have
  been shipping with f2fs. Some of them were related to hardware
  encryption support which are actually not an issue in mainline, but
  would be better to merge them in order to avoid potential bugs.

  Enhancements:
   - do GC sub-sections when the section is large
   - add a flag in ioctl(SHUTDOWN) to trigger fsck for QA
   - use kvmalloc() in order to give another chance to avoid ENOMEM

  Bug fixes:
   - fix accessing memory boundaries in a malformed iamge
   - GC gives stale unencrypted block
   - GC counts in large sections
   - detect idle time more precisely
   - block allocation of DIO writes
   - race conditions between write_begin and write_checkpoint
   - allow GCs for node segments via ioctl()

  There are various clean-ups and minor bug fixes as well"

* tag 'f2fs-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (43 commits)
  f2fs: sanity check of xattr entry size
  f2fs: fix use-after-free issue when accessing sbi->stat_info
  f2fs: check PageWriteback flag for ordered case
  f2fs: fix validation of the block count in sanity_check_raw_super
  f2fs: fix missing unlock(sbi->gc_mutex)
  f2fs: fix to dirty inode synchronously
  f2fs: clean up structure extent_node
  f2fs: fix block address for __check_sit_bitmap
  f2fs: fix sbi->extent_list corruption issue
  f2fs: clean up checkpoint flow
  f2fs: flush stale issued discard candidates
  f2fs: correct wrong spelling, issing_*
  f2fs: use kvmalloc, if kmalloc is failed
  f2fs: remove redundant comment of unused wio_mutex
  f2fs: fix to reorder set_page_dirty and wait_on_page_writeback
  f2fs: clear PG_writeback if IPU failed
  f2fs: add an ioctl() to explicitly trigger fsck later
  f2fs: avoid frequent costly fsck triggers
  f2fs: fix m_may_create to make OPU DIO write correctly
  f2fs: fix to update new block address correctly for OPU
  ...