From f151f86dc64467f3333724d503a40c9484b07021 Mon Sep 17 00:00:00 2001
From: ian <ian@ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f>
Date: Sat, 6 May 2017 16:06:33 +0000
Subject: [PATCH] MFC r230208, r230252, r234346:

  Add nfs export support to tmpfs(5)

  Return EOPNOTSUPP since we only support update mounts for NFS export.

  tmpfs: Allow update mounts only for certain options.
  Since r230208 update mounts were allowed if the list of mount options
  contained the "export" option. This is not correct as tmpfs doesn't really
  support updating all options.


git-svn-id: svn://svn.freebsd.org/base/stable/8@317883 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
---
 sys/fs/tmpfs/tmpfs.h        |  3 +++
 sys/fs/tmpfs/tmpfs_vfsops.c | 16 ++++++++++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/sys/fs/tmpfs/tmpfs.h b/sys/fs/tmpfs/tmpfs.h
index 85eaee129..fc59bb841 100644
--- a/sys/fs/tmpfs/tmpfs.h
+++ b/sys/fs/tmpfs/tmpfs.h
@@ -389,6 +389,9 @@ struct tmpfs_mount {
 	 * tmpfs_pool.c. */
 	uma_zone_t		tm_dirent_pool;
 	uma_zone_t		tm_node_pool;
+
+	/* Read-only status. */
+	int			tm_ronly;
 };
 #define TMPFS_LOCK(tm) mtx_lock(&(tm)->allnode_lock)
 #define TMPFS_UNLOCK(tm) mtx_unlock(&(tm)->allnode_lock)
diff --git a/sys/fs/tmpfs/tmpfs_vfsops.c b/sys/fs/tmpfs/tmpfs_vfsops.c
index ae96c8296..4db3d348e 100644
--- a/sys/fs/tmpfs/tmpfs_vfsops.c
+++ b/sys/fs/tmpfs/tmpfs_vfsops.c
@@ -81,6 +81,10 @@ static const char *tmpfs_opts[] = {
 	NULL
 };
 
+static const char *tmpfs_updateopts[] = {
+	"from", "export", NULL
+};
+
 /* --------------------------------------------------------------------- */
 
 static int
@@ -149,10 +153,13 @@ tmpfs_mount(struct mount *mp)
 		return (EINVAL);
 
 	if (mp->mnt_flag & MNT_UPDATE) {
-		/* XXX: There is no support yet to update file system
-		 * settings.  Should be added. */
-
-		return EOPNOTSUPP;
+		/* Only support update mounts for certain options. */
+		if (vfs_filteropt(mp->mnt_optnew, tmpfs_updateopts) != 0)
+			return (EOPNOTSUPP);
+		if (vfs_flagopt(mp->mnt_optnew, "ro", NULL, 0) !=
+		    ((struct tmpfs_mount *)mp->mnt_data)->tm_ronly)
+			return (EOPNOTSUPP);
+		return (0);
 	}
 
 	vn_lock(mp->mnt_vnodecovered, LK_SHARED | LK_RETRY);
@@ -224,6 +231,7 @@ tmpfs_mount(struct mount *mp)
 	    tmpfs_node_ctor, tmpfs_node_dtor,
 	    tmpfs_node_init, tmpfs_node_fini,
 	    UMA_ALIGN_PTR, 0);
+	tmp->tm_ronly = (mp->mnt_flag & MNT_RDONLY) != 0;
 
 	/* Allocate the root node. */
 	error = tmpfs_alloc_node(tmp, VDIR, root_uid,
-- 
2.42.0