1 files changed, 41 insertions, 0 deletions
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 1e972f884a81..9dc748abdf33 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -3877,3 +3877,44 @@ xlog_drop_incompat_feat(
 {
 	up_read(&log->l_incompat_users);
 }
+
+/*
+ * Get permission to use log-assisted atomic exchange of file extents.
+ *
+ * Callers must not be running any transactions or hold any inode locks, and
+ * they must release the permission by calling xlog_drop_incompat_feat
+ * when they're done.
+ */
+int
+xfs_attr_use_log_assist(
+	struct xfs_mount	*mp)
+{
+	int			error = 0;
+
+	/*
+	 * Protect ourselves from an idle log clearing the logged xattrs log
+	 * incompat feature bit.
+	 */
+	xlog_use_incompat_feat(mp->m_log);
+
+	/*
+	 * If log-assisted xattrs are already enabled, the caller can use the
+	 * log assisted swap functions with the log-incompat reference we got.
+	 */
+	if (xfs_sb_version_haslogxattrs(&mp->m_sb))
+		return 0;
+
+	/* Enable log-assisted xattrs. */
+	error = xfs_add_incompat_log_feature(mp,
+			XFS_SB_FEAT_INCOMPAT_LOG_XATTRS);
+	if (error)
+		goto drop_incompat;
+
+	xfs_warn_once(mp,
+"EXPERIMENTAL logged extended attributes feature added. Use at your own risk!");
+
+	return 0;
+drop_incompat:
+	xlog_drop_incompat_feat(mp->m_log);
+	return error;
+}