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From: Christoph Hellwig <hch@lst.de>
To: linux-xfs@vger.kernel.org
Subject: [PATCH 1/2] xfs: refactor xfs_file_fsync
Date: Mon, 11 Jan 2021 17:15:43 +0100
Message-ID: <20210111161544.1414409-2-hch@lst.de> (raw)
In-Reply-To: <20210111161544.1414409-1-hch@lst.de>

Factor out the log syncing logic into two helpers to make the code easier
to read and more maintainable.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_file.c | 81 +++++++++++++++++++++++++++++------------------
 1 file changed, 50 insertions(+), 31 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5b0f93f738372d..414d856e2e755a 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -118,6 +118,54 @@ xfs_dir_fsync(
 	return xfs_log_force_inode(ip);
 }
 
+static xfs_lsn_t
+xfs_fsync_lsn(
+	struct xfs_inode	*ip,
+	bool			datasync)
+{
+	if (!xfs_ipincount(ip))
+		return 0;
+	if (datasync && !(ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
+		return 0;
+	return ip->i_itemp->ili_last_lsn;
+}
+
+/*
+ * All metadata updates are logged, which means that we just have to flush the
+ * log up to the latest LSN that touched the inode.
+ *
+ * If we have concurrent fsync/fdatasync() calls, we need them to all block on
+ * the log force before we clear the ili_fsync_fields field. This ensures that
+ * we don't get a racing sync operation that does not wait for the metadata to
+ * hit the journal before returning.  If we race with clearing ili_fsync_fields,
+ * then all that will happen is the log force will do nothing as the lsn will
+ * already be on disk.  We can't race with setting ili_fsync_fields because that
+ * is done under XFS_ILOCK_EXCL, and that can't happen because we hold the lock
+ * shared until after the ili_fsync_fields is cleared.
+ */
+static  int
+xfs_fsync_flush_log(
+	struct xfs_inode	*ip,
+	bool			datasync,
+	int			*log_flushed)
+{
+	int			error = 0;
+	xfs_lsn_t		lsn;
+
+	xfs_ilock(ip, XFS_ILOCK_SHARED);
+	lsn = xfs_fsync_lsn(ip, datasync);
+	if (lsn) {
+		error = xfs_log_force_lsn(ip->i_mount, lsn, XFS_LOG_SYNC,
+					  log_flushed);
+
+		spin_lock(&ip->i_itemp->ili_lock);
+		ip->i_itemp->ili_fsync_fields = 0;
+		spin_unlock(&ip->i_itemp->ili_lock);
+	}
+	xfs_iunlock(ip, XFS_ILOCK_SHARED);
+	return error;
+}
+
 STATIC int
 xfs_file_fsync(
 	struct file		*file,
@@ -125,13 +173,10 @@ xfs_file_fsync(
 	loff_t			end,
 	int			datasync)
 {
-	struct inode		*inode = file->f_mapping->host;
-	struct xfs_inode	*ip = XFS_I(inode);
-	struct xfs_inode_log_item *iip = ip->i_itemp;
+	struct xfs_inode	*ip = XFS_I(file->f_mapping->host);
 	struct xfs_mount	*mp = ip->i_mount;
 	int			error = 0;
 	int			log_flushed = 0;
-	xfs_lsn_t		lsn = 0;
 
 	trace_xfs_file_fsync(ip);
 
@@ -155,33 +200,7 @@ xfs_file_fsync(
 	else if (mp->m_logdev_targp != mp->m_ddev_targp)
 		xfs_blkdev_issue_flush(mp->m_ddev_targp);
 
-	/*
-	 * All metadata updates are logged, which means that we just have to
-	 * flush the log up to the latest LSN that touched the inode. If we have
-	 * concurrent fsync/fdatasync() calls, we need them to all block on the
-	 * log force before we clear the ili_fsync_fields field. This ensures
-	 * that we don't get a racing sync operation that does not wait for the
-	 * metadata to hit the journal before returning. If we race with
-	 * clearing the ili_fsync_fields, then all that will happen is the log
-	 * force will do nothing as the lsn will already be on disk. We can't
-	 * race with setting ili_fsync_fields because that is done under
-	 * XFS_ILOCK_EXCL, and that can't happen because we hold the lock shared
-	 * until after the ili_fsync_fields is cleared.
-	 */
-	xfs_ilock(ip, XFS_ILOCK_SHARED);
-	if (xfs_ipincount(ip)) {
-		if (!datasync ||
-		    (iip->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
-			lsn = iip->ili_last_lsn;
-	}
-
-	if (lsn) {
-		error = xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, &log_flushed);
-		spin_lock(&iip->ili_lock);
-		iip->ili_fsync_fields = 0;
-		spin_unlock(&iip->ili_lock);
-	}
-	xfs_iunlock(ip, XFS_ILOCK_SHARED);
+	error = xfs_fsync_flush_log(ip, datasync, &log_flushed);
 
 	/*
 	 * If we only have a single device, and the log force about was
-- 
2.29.2


  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-11 16:15 avoid taking the iolock in fsync unless actually needed Christoph Hellwig
2021-01-11 16:15 ` Christoph Hellwig [this message]
2021-01-12 15:33   ` [PATCH 1/2] xfs: refactor xfs_file_fsync Brian Foster
2021-01-12 17:12     ` Christoph Hellwig
2021-01-11 16:15 ` [PATCH 2/2] xfs: reduce ilock acquisitions in xfs_file_fsync Christoph Hellwig
2021-01-12 15:34   ` Brian Foster
2021-01-22 16:46 avoid taking the iolock in fsync unless actually needed v2 Christoph Hellwig
2021-01-22 16:46 ` [PATCH 1/2] xfs: refactor xfs_file_fsync Christoph Hellwig
2021-01-22 21:08   ` Dave Chinner

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