[PATCH v2] xfs: various log stuff...

From: Dave Chinner <david@fromorbit.com>
To: linux-xfs@vger.kernel.org
Subject: [PATCH v2] xfs: various log stuff...
Date: Tue, 23 Feb 2021 14:34:34 +1100	[thread overview]
Message-ID: <20210223033442.3267258-1-david@fromorbit.com> (raw)

HI folks,

Version 2 of this set of changes to the log code. First version
was posted here:

https://lore.kernel.org/linux-xfs/20210128044154.806715-1-david@fromorbit.com/

"Quick patch dump for y'all. A couple of minor cleanups to the
log behaviour, a fix for the CIL throttle hang and a couple of
patches to rework the cache flushing that journal IO does to reduce
the number of cache flushes by a couple of orders of magnitude."

Version 2:
- fix ticket reservation roundoff to include 2 roundoffs
- removed stale copied comment from roundoff initialisation.
- clarified "separation" to mean "separation for ordering purposes" in commit
  message.
- added comment that newly activated, clean, empty iclogs have a LSN of 0 so are
  captured by the "iclog lsn < start_lsn" case that avoids needing to wait
  before releasing the commit iclog to be written.
- added async cache flush infrastructure
- convert CIL checkpoint push work it issue an unconditional metadata device
  cache flush rather than asking the first iclog write to issue it via
  REQ_PREFLUSH.
- cleaned up xlog_write() to remove a redundant parameter and prepare the logic
  for setting flags on the iclog based on the type of operational data is being
  written to the log.
- added XLOG_ICL_NEED_FUA flag to complement the NEED_FLUSH flag, allowing
  callers to issue explicit flushes and clear the NEED_FLUSH flag before the
  iclog is written without dropping the REQ_FUA requirement in /dev/null...
- added CIL commit-in-start-iclog optimisation that clears the NEED_FLUSH flag
  to avoid an unnecessary cache flush when issuing the iclog.
- fixed typo in CIL throttle bugfix comment.
- fixed trailing whitespace in commit message.