linux-kernel - [PATCH 31/35] union-mount: Implement union-aware chown()

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Message-Id: <1271372682-21225-32-git-send-email-vaurora@redhat.com>
Date:	Thu, 15 Apr 2010 16:04:38 -0700
From:	Valerie Aurora <vaurora@...hat.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Valerie Aurora <vaurora@...hat.com>
Subject: [PATCH 31/35] union-mount: Implement union-aware chown()

Proof-of-concept implementation of chown() for union mounts.
---
 fs/open.c |   24 +++++++++++++++++++++---
 1 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 686fcd2..325852d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -30,6 +30,7 @@
 #include <linux/falloc.h>
 #include <linux/fs_struct.h>
 #include <linux/ima.h>
+#include <linux/union.h>
 
 #include "internal.h"
 
@@ -717,18 +718,35 @@ static int chown_common(struct path *path, uid_t user, gid_t group)
 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 {
 	struct path path;
+	struct nameidata nd;
+	struct vfsmount *mnt;
+	char *tmp;
 	int error;
 
-	error = user_path(filename, &path);
+	error = user_path_nd(AT_FDCWD, filename, LOOKUP_FOLLOW,
+				     &nd, &path, &tmp);
 	if (error)
 		goto out;
-	error = mnt_want_write(path.mnt);
+
+	if (IS_UNIONED_DIR(&nd.path))
+		mnt = nd.path.mnt;
+	else
+		mnt = path.mnt;
+
+	error = mnt_want_write(mnt);
 	if (error)
 		goto out_release;
+
+	error = union_copyup(&nd, &path);
+	if (error)
+		goto out_drop_write;
 	error = chown_common(&path, user, group);
-	mnt_drop_write(path.mnt);
+out_drop_write:
+	mnt_drop_write(mnt);
 out_release:
 	path_put(&path);
+	path_put(&nd.path);
+	putname(tmp);
 out:
 	return error;
 }
-- 
1.6.3.3

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