Merge tag 'afs-cachefiles-fixes-20210323' of git://git.kernel.org/pub/scm/linux/kerne...

Pull cachefiles and afs fixes from David Howells:
 "Fixes from Matthew Wilcox for page waiting-related issues in
  cachefiles and afs as extracted from his folio series[1]:

   - In cachefiles, remove the use of the wait_bit_key struct to access
     something that's actually in wait_page_key format. The proper
     struct is now available in the header, so that should be used
     instead.

   - Add a proper wait function for waiting killably on the page
     writeback flag. This includes a recent bugfix[2] that's not in the
     afs code.

   - In afs, use the function added in (2) rather than using
     wait_on_page_bit_killable() which doesn't provide the
     aforementioned bugfix"

Link: https://lore.kernel.org/r/20210320054104.1300774-1-willy@infradead.org[1]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c2407cf7d22d0c0d94cf20342b3b8f06f1d904e7
Link: https://lore.kernel.org/r/20210323120829.GC1719932@casper.infradead.org/
* tag 'afs-cachefiles-fixes-20210323' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  afs: Use wait_on_page_writeback_killable
  mm/writeback: Add wait_on_page_writeback_killable
  fs/cachefiles: Remove wait_bit_key layout dependency