git: 4a4b059a9795 - main - Add vfs_remount_ro()

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=4a4b059a97950740f04b091d7050460a984e7555

commit 4a4b059a97950740f04b091d7050460a984e7555
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2021-12-25 19:44:59 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2022-01-08 03:41:44 +0000

    Add vfs_remount_ro()
    
    a helper to remount filesystem from rw to ro.
    
    Tested by:      pho
    Reviewed by:    markj, mckusick
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D33721
---
 sys/kern/vfs_mount.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 sys/sys/mount.h      |  2 ++
 2 files changed, 91 insertions(+)

diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index ee163a5e8137..61c239cf65b3 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -2868,6 +2868,95 @@ mount_devctl_event(const char *type, struct mount *mp, bool donew)
 	free(buf, M_MOUNT);
 }
 
+/*
+ * Force remount specified mount point to read-only.  The argument
+ * must be busied to avoid parallel unmount attempts.
+ *
+ * Intended use is to prevent further writes if some metadata
+ * inconsistency is detected.  Note that the function still flushes
+ * all cached metadata and data for the mount point, which might be
+ * not always suitable.
+ */
+int
+vfs_remount_ro(struct mount *mp)
+{
+	struct vfsoptlist *opts;
+	struct vfsopt *opt;
+	struct vnode *vp_covered, *rootvp;
+	int error;
+
+	KASSERT(mp->mnt_lockref > 0,
+	    ("vfs_remount_ro: mp %p is not busied", mp));
+	KASSERT((mp->mnt_kern_flag & MNTK_UNMOUNT) == 0,
+	    ("vfs_remount_ro: mp %p is being unmounted (and busy?)", mp));
+
+	rootvp = NULL;
+	vp_covered = mp->mnt_vnodecovered;
+	error = vget(vp_covered, LK_EXCLUSIVE | LK_NOWAIT);
+	if (error != 0)
+		return (error);
+	VI_LOCK(vp_covered);
+	if ((vp_covered->v_iflag & VI_MOUNT) != 0) {
+		VI_UNLOCK(vp_covered);
+		vput(vp_covered);
+		return (EBUSY);
+	}
+	vp_covered->v_iflag |= VI_MOUNT;
+	VI_UNLOCK(vp_covered);
+	vfs_op_enter(mp);
+	vn_seqc_write_begin(vp_covered);
+
+	MNT_ILOCK(mp);
+	if ((mp->mnt_flag & MNT_RDONLY) != 0) {
+		MNT_IUNLOCK(mp);
+		error = EBUSY;
+		goto out;
+	}
+	mp->mnt_flag |= MNT_UPDATE | MNT_FORCE | MNT_RDONLY;
+	rootvp = vfs_cache_root_clear(mp);
+	MNT_IUNLOCK(mp);
+
+	opts = malloc(sizeof(struct vfsoptlist), M_MOUNT, M_WAITOK | M_ZERO);
+	TAILQ_INIT(opts);
+	opt = malloc(sizeof(struct vfsopt), M_MOUNT, M_WAITOK | M_ZERO);
+	opt->name = strdup("ro", M_MOUNT);
+	opt->value = NULL;
+	TAILQ_INSERT_TAIL(opts, opt, link);
+	vfs_mergeopts(opts, mp->mnt_opt);
+	mp->mnt_optnew = opts;
+
+	error = VFS_MOUNT(mp);
+
+	if (error == 0) {
+		MNT_ILOCK(mp);
+		mp->mnt_flag &= ~(MNT_UPDATE | MNT_FORCE);
+		MNT_IUNLOCK(mp);
+		vfs_deallocate_syncvnode(mp);
+		if (mp->mnt_opt != NULL)
+			vfs_freeopts(mp->mnt_opt);
+		mp->mnt_opt = mp->mnt_optnew;
+	} else {
+		MNT_ILOCK(mp);
+		mp->mnt_flag &= ~(MNT_UPDATE | MNT_FORCE | MNT_RDONLY);
+		MNT_IUNLOCK(mp);
+		vfs_freeopts(mp->mnt_optnew);
+	}
+	mp->mnt_optnew = NULL;
+
+out:
+	vfs_op_exit(mp);
+	VI_LOCK(vp_covered);
+	vp_covered->v_iflag &= ~VI_MOUNT;
+	VI_UNLOCK(vp_covered);
+	vput(vp_covered);
+	vn_seqc_write_end(vp_covered);
+	if (rootvp != NULL) {
+		vn_seqc_write_end(rootvp);
+		vrele(rootvp);
+	}
+	return (error);
+}
+
 /*
  * Suspend write operations on all local writeable filesystems.  Does
  * full sync of them in the process.
diff --git a/sys/sys/mount.h b/sys/sys/mount.h
index 1b4243788f7b..ae3eebd94c53 100644
--- a/sys/sys/mount.h
+++ b/sys/sys/mount.h
@@ -1036,6 +1036,8 @@ void	vfs_register_for_notification(struct mount *, struct mount *,
 void	vfs_unregister_for_notification(struct mount *,
 	    struct mount_upper_node *);
 void	vfs_unregister_upper(struct mount *, struct mount_upper_node *);
+int	vfs_remount_ro(struct mount *mp);
+
 extern	TAILQ_HEAD(mntlist, mount) mountlist;	/* mounted filesystem list */
 extern	struct mtx_padalign mountlist_mtx;
 extern	struct nfs_public nfs_pub;