linux-kernel - [PATCH 03/16] vfs: Implement vfs_loopback

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Message-Id: <1460734532-20134-3-git-send-email-ebiederm@xmission.com>
Date:	Fri, 15 Apr 2016 10:35:19 -0500
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>, security@...ian.org,
	security@...nel.org, Al Viro <viro@...iv.linux.org.uk>,
	security@...ntu.com, Peter Hurley <peter@...leysoftware.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Willy Tarreau <w@....eu>,
	Aurelien Jarno <aurelien@...el32.net>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Jann Horn <jann@...jh.net>, Greg KH <greg@...ah.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.com>,
	Florian Weimer <fw@...eb.enyo.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 03/16] vfs: Implement vfs_loopback_mount

Add a helper to turn a struct path into a mount.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 fs/namespace.c        | 9 +++++++++
 include/linux/mount.h | 1 +
 2 files changed, 10 insertions(+)

diff --git a/fs/namespace.c b/fs/namespace.c
index 4fb1691b4355..714778360c2b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1047,6 +1047,15 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
 	return ERR_PTR(err);
 }
 
+struct vfsmount *vfs_loopback_mount(struct path *path)
+{
+	struct mount *p;
+	p = clone_mnt(real_mount(path->mnt), path->dentry, 0);
+	if (IS_ERR(p))
+		return ERR_CAST(p);
+	return &p->mnt;
+}
+
 static void cleanup_mnt(struct mount *mnt)
 {
 	/*
diff --git a/include/linux/mount.h b/include/linux/mount.h
index f822c3c11377..8f6039ad898e 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -89,6 +89,7 @@ struct file_system_type;
 extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
 				      int flags, const char *name,
 				      void *data);
+struct vfsmount *vfs_loopback_mount(struct path *path);
 
 extern void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list);
 extern void mark_mounts_for_expiry(struct list_head *mounts);
-- 
2.8.1