Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2021-07-19' into staging

Block patches for 6.1-rc0:
- Make blkdebug's suspend/resume handling robust (and thread-safe)

# gpg: Signature made Mon 19 Jul 2021 18:25:48 BST
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2021-07-19:
  blkdebug: protect rules and suspended_reqs with a lock
  block/blkdebug: remove new_state field and instead use a local variable
  blkdebug: do not suspend in the middle of QLIST_FOREACH_SAFE
  blkdebug: track all actions
  blkdebug: move post-resume handling to resume_req_by_tag
  blkdebug: refactor removal of a suspended request

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>