fs: add a vfs_fchmod helper

Add a helper for struct file based chmode operations.  To be used by
the initramfs code soon.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/open.c

@@ -602,14 +602,19 @@ static int chmod_common(const struct path *path, umode_t mode)
 	return error;
 }
 
+int vfs_fchmod(struct file *file, umode_t mode)
+{
+	audit_file(file);
+	return chmod_common(&file->f_path, mode);
+}
+
 int ksys_fchmod(unsigned int fd, umode_t mode)
 {
 	struct fd f = fdget(fd);
 	int err = -EBADF;
 
 	if (f.file) {
-		audit_file(f.file);
-		err = chmod_common(&f.file->f_path, mode);
+		err = vfs_fchmod(f.file, mode);
 		fdput(f);
 	}
 	return err;

include/linux/fs.h

@@ -1745,6 +1745,7 @@ int vfs_mkobj(struct dentry *, umode_t,
 		void *);
 
 int vfs_fchown(struct file *file, uid_t user, gid_t group);
+int vfs_fchmod(struct file *file, umode_t mode);
 
 extern long vfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);