From: Dave Chinner dchinner@redhat.com
mainline-inclusion from mainline-v5.14-rc1 commit 8191d8222c514c69a8e1ac46bd9812b9e0aab7d0 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4KIAO CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
------------------------------------------------- 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 Signed-off-by: Guo Xuenan guoxuenan@huawei.com Reviewed-by: Lihong Kou koulihong@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- fs/xfs/xfs_log.c | 42 +++++++++++++++++++++++++++++++++++++----- 1 file changed, 37 insertions(+), 5 deletions(-)
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index fa9408e965a7..447a8903dd06 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -3050,6 +3050,35 @@ 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. * @@ -3084,7 +3113,6 @@ 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_); @@ -3111,11 +3139,12 @@ 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 { /* @@ -3155,6 +3184,7 @@ xlog_force_lsn( bool already_slept) { struct xlog_in_core *iclog; + bool completed;
spin_lock(&log->l_icloglock); iclog = log->l_iclog; @@ -3191,10 +3221,12 @@ 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: /*