Merge tag 'xfs-4.13-fixes-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

Pull xfs fixes from Darrick Wong:

 - fix firstfsb variables that we left uninitialized, which could lead
   to locking problems.

 - check for NULL metadata buffer pointers before using them.

 - don't allow btree cursor manipulation if the btree block is corrupt.
   Better to just shut down.

 - fix infinite loop problems in quotacheck.

 - fix buffer overrun when validating directory blocks.

 - fix deadlock problem in bunmapi.

* tag 'xfs-4.13-fixes-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: fix multi-AG deadlock in xfs_bunmapi
  xfs: check that dir block entries don't off the end of the buffer
  xfs: fix quotacheck dquot id overflow infinite loop
  xfs: check _alloc_read_agf buffer pointer before using
  xfs: set firstfsb to NULLFSBLOCK before feeding it to _bmapi_write
  xfs: check _btree_check_block value