do_dentry_open(): take initialization of file->f_path to caller

... and get rid of a couple of arguments and a pointless reassignment
in finish_open() case.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/open.c

@@ -667,8 +667,7 @@ int open_check_o_direct(struct file *f)
 	return 0;
 }
 
-static int do_dentry_open(struct dentry *dentry, struct vfsmount *mnt,
-			  struct file *f,
+static int do_dentry_open(struct file *f,
 			  int (*open)(struct inode *, struct file *),
 			  const struct cred *cred)
 {
@@ -682,18 +681,16 @@ static int do_dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 	if (unlikely(f->f_flags & O_PATH))
 		f->f_mode = FMODE_PATH;
 
-	inode = dentry->d_inode;
+	inode = f->f_path.dentry->d_inode;
 	if (f->f_mode & FMODE_WRITE) {
-		error = __get_file_write_access(inode, mnt);
+		error = __get_file_write_access(inode, f->f_path.mnt);
 		if (error)
 			goto cleanup_file;
 		if (!special_file(inode->i_mode))
 			file_take_write(f);
 	}
 
 	f->f_mapping = inode->i_mapping;
-	f->f_path.dentry = dentry;
-	f->f_path.mnt = mnt;
 	f->f_pos = 0;
 	file_sb_list_add(f, inode->i_sb);
 
@@ -740,15 +737,14 @@ static int do_dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 			 * here, so just reset the state.
 			 */
 			file_reset_write(f);
-			mnt_drop_write(mnt);
+			mnt_drop_write(f->f_path.mnt);
 		}
 	}
 	file_sb_list_del(f);
-	f->f_path.dentry = NULL;
-	f->f_path.mnt = NULL;
 cleanup_file:
-	dput(dentry);
-	mntput(mnt);
+	path_put(&f->f_path);
+	f->f_path.mnt = NULL;
+	f->f_path.dentry = NULL;
 	return error;
 }
 
@@ -771,9 +767,9 @@ int finish_open(struct file *file, struct dentry *dentry,
 	BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
 
 	mntget(file->f_path.mnt);
-	dget(dentry);
+	file->f_path.dentry = dget(dentry);
 
-	error = do_dentry_open(dentry, file->f_path.mnt, file, open, current_cred());
+	error = do_dentry_open(file, open, current_cred());
 	if (!error)
 		*opened |= FILE_OPENED;
 
@@ -821,7 +817,9 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
 	}
 
 	f->f_flags = flags;
-	error = do_dentry_open(dentry, mnt, f, NULL, cred);
+	f->f_path.mnt = mnt;
+	f->f_path.dentry = dentry;
+	error = do_dentry_open(f, NULL, cred);
 	if (!error) {
 		error = open_check_o_direct(f);
 		if (error) {