Merge tag 'errseq-v4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton...

Pull errseq infrastructure fix from Jeff Layton:
 "The PostgreSQL developers recently had a spirited discussion about the
  writeback error handling in Linux, and reached out to us about a
  behavoir change to the code that bit them when the errseq_t changes
  were merged.

  When we changed to using errseq_t for tracking writeback errors, we
  lost the ability for an application to see a writeback error that
  occurred before the open on which the fsync was issued. This was
  problematic for PostgreSQL which offloads fsync calls to a completely
  separate process from the DB writers.

  This patch restores that ability. If the errseq_t value in the inode
  does not have the SEEN flag set, then we just return 0 for the sample.
  That ensures that any recorded error is always delivered at least
  once.

  Note that we might still lose the error if the inode gets evicted from
  the cache before anything can reopen it, but that was the case before
  errseq_t was merged. At LSF/MM we had some discussion about keeping
  inodes with unreported writeback errors around in the cache for longer
  (possibly indefinitely), but that's really a separate problem"

* tag 'errseq-v4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  errseq: Always report a writeback error once