Commit 8191d822 authored by Dave Chinner's avatar Dave Chinner Committed by Darrick J. Wong
Browse files

xfs: avoid unnecessary waits in xfs_log_force_lsn() 



Before waiting on a iclog in xfs_log_force_lsn(), we don't check to
see if the iclog has already been completed and the contents on
stable storage. We check for completed iclogs in xfs_log_force(), so
we should do the same thing for xfs_log_force_lsn().

This fixed some random up-to-30s pauses seen in unmounting
filesystems in some tests. A log force ends up waiting on completed
iclog, and that doesn't then get flushed (and hence the log force
get completed) until the background log worker issues a log force
that flushes the iclog in question. Then the unmount unblocks and
continues.

Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>
parent 2bf1ec0f

fs/xfs/xfs_log.c

+37 −5
Original line number Diff line number Diff line
@@ -3143,6 +3143,35 @@ xlog_state_switch_iclogs( 
	log->l_iclog = iclog->ic_next;

}



/*

 * Force the iclog to disk and check if the iclog has been completed before

 * xlog_force_iclog() returns. This can happen on synchronous (e.g.

 * pmem) or fast async storage because we drop the icloglock to issue the IO.

 * If completion has already occurred, tell the caller so that it can avoid an

 * unnecessary wait on the iclog.

 */

static int

xlog_force_and_check_iclog(

	struct xlog_in_core	*iclog,

	bool			*completed)

{

	xfs_lsn_t		lsn = be64_to_cpu(iclog->ic_header.h_lsn);

	int			error;



	*completed = false;

	error = xlog_force_iclog(iclog);

	if (error)

		return error;



	/*

	 * If the iclog has already been completed and reused the header LSN

	 * will have been rewritten by completion

	 */

	if (be64_to_cpu(iclog->ic_header.h_lsn) != lsn)

		*completed = true;

	return 0;

}



/*

 * Write out all data in the in-core log as of this exact moment in time.

 *
@@ -3177,7 +3206,6 @@ xfs_log_force( 
{

	struct xlog		*log = mp->m_log;

	struct xlog_in_core	*iclog;

	xfs_lsn_t		lsn;



	XFS_STATS_INC(mp, xs_log_force);

	trace_xfs_log_force(mp, 0, _RET_IP_);
@@ -3206,11 +3234,12 @@ xfs_log_force( 
	} else if (iclog->ic_state == XLOG_STATE_ACTIVE) {

		if (atomic_read(&iclog->ic_refcnt) == 0) {

			/* We have exclusive access to this iclog. */

			lsn = be64_to_cpu(iclog->ic_header.h_lsn);

			if (xlog_force_iclog(iclog))

			bool	completed;



			if (xlog_force_and_check_iclog(iclog, &completed))

				goto out_error;



			if (be64_to_cpu(iclog->ic_header.h_lsn) != lsn)

			if (completed)

				goto out_unlock;

		} else {

			/*
@@ -3250,6 +3279,7 @@ xlog_force_lsn( 
	bool			already_slept)

{

	struct xlog_in_core	*iclog;

	bool			completed;



	spin_lock(&log->l_icloglock);

	iclog = log->l_iclog;
@@ -3287,10 +3317,12 @@ xlog_force_lsn( 
					&log->l_icloglock);

			return -EAGAIN;

		}

		if (xlog_force_iclog(iclog))

		if (xlog_force_and_check_iclog(iclog, &completed))

			goto out_error;

		if (log_flushed)

			*log_flushed = 1;

		if (completed)

			goto out_unlock;

		break;

	case XLOG_STATE_WANT_SYNC:

		/*