[RFC][PATCH 06/27] elevate write count during entire ncp_ioctl()

[Dave Hansen <haveblue@us.ibm.com>]

Some ioctls need write access, but others don't.  Make a helper
function to decode when write access is needed, and take it.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

 fs/nfsd/vfs.c             |    0 
 lxc-dave/fs/ncpfs/ioctl.c |   54 +++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 53 insertions(+), 1 deletion(-)

diff -puN fs/namei.c~elevate-writers-file_permission-callers fs/namei.c
diff -puN fs/open.c~elevate-writers-file_permission-callers fs/open.c
diff -puN fs/exec.c~elevate-writers-file_permission-callers fs/exec.c
diff -puN fs/ncpfs/ioctl.c~elevate-writers-file_permission-callers fs/ncpfs/ioctl.c
--- lxc/fs/ncpfs/ioctl.c~elevate-writers-file_permission-callers	2006-06-07 16:53:15.000000000 -0700
+++ lxc-dave/fs/ncpfs/ioctl.c	2006-06-07 16:53:15.000000000 -0700
@@ -183,7 +183,7 @@ ncp_get_charsets(struct ncp_server* serv
 }
 #endif /* CONFIG_NCPFS_NLS */
 
-int ncp_ioctl(struct inode *inode, struct file *filp,
+static int __ncp_ioctl(struct inode *inode, struct file *filp,
 	      unsigned int cmd, unsigned long arg)
 {
 	struct ncp_server *server = NCP_SERVER(inode);
@@ -654,3 +654,55 @@ outrel:			
 /* #endif */
 	return -EINVAL;
 }
+
+static int ncp_ioctl_need_write(unsigned int cmd)
+{
+	switch (cmd) {
+        case NCP_IOC_GET_FS_INFO:
+        case NCP_IOC_GET_FS_INFO_V2:
+        case NCP_IOC_NCPREQUEST:
+        case NCP_IOC_SETDENTRYTTL:
+        case NCP_IOC_SIGN_INIT:
+        case NCP_IOC_LOCKUNLOCK:
+        case NCP_IOC_SET_SIGN_WANTED:
+		return 0;
+        case NCP_IOC_GETOBJECTNAME:
+        case NCP_IOC_SETOBJECTNAME:
+        case NCP_IOC_GETPRIVATEDATA:
+        case NCP_IOC_SETPRIVATEDATA:
+        case NCP_IOC_SETCHARSETS:
+        case NCP_IOC_GETCHARSETS:
+        case NCP_IOC_CONN_LOGGED_IN:
+        case NCP_IOC_GETDENTRYTTL:
+        case NCP_IOC_GETMOUNTUID2:
+        case NCP_IOC_SIGN_WANTED:
+        case NCP_IOC_GETROOT:
+        case NCP_IOC_SETROOT:
+		return 0;
+	default:
+		/* unkown IOCTL command, assume write */
+		WARN_ON();
+	}
+	return 1;
+}
+
+int ncp_ioctl(struct inode *inode, struct file *filp,
+	      unsigned int cmd, unsigned long arg)
+{
+	int ret;
+
+	if (ncp_ioctl_need_write(cmd)) {
+		/*
+		 * inside the ioctl(), any failures which
+		 * are because of file_permission() are
+		 * -EACCESS, so it seems consistent to keep
+		 *  that here.
+		 */
+		if (mnt_want_write(filp->f_vfsmnt))
+			return -EACCESS;
+	}
+	ret = __ncp_ioctl(inode, filp, cmd, arg);
+	if (ncp_ioctl_need_write(cmd)
+		mnt_drop_write(filp->->f_vfsmnt;
+	return ret;
+}
diff -puN fs/nfsd/vfs.c~elevate-writers-file_permission-callers fs/nfsd/vfs.c
_