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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: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
This commit is contained in:
Dave Chinner 2021-07-27 16:23:49 -07:00 committed by Darrick J. Wong
parent 2bf1ec0ff0
commit 8191d8222c
1 changed files with 37 additions and 5 deletions
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42
fs/xfs/xfs_log.c
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@ -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:
/*