From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97F8EC55ABD for ; Tue, 10 Nov 2020 20:04:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41F882067D for ; Tue, 10 Nov 2020 20:04:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730894AbgKJUEo (ORCPT ); Tue, 10 Nov 2020 15:04:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726861AbgKJUEo (ORCPT ); Tue, 10 Nov 2020 15:04:44 -0500 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 48BF1C0613D1; Tue, 10 Nov 2020 12:04:43 -0800 (PST) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kcZsB-0031DR-RH; Tue, 10 Nov 2020 20:04:11 +0000 Date: Tue, 10 Nov 2020 20:04:11 +0000 From: Al Viro To: yulei.kernel@gmail.com Cc: akpm@linux-foundation.org, naoya.horiguchi@nec.com, pbonzini@redhat.com, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, xiaoguangrong.eric@gmail.com, kernellwp@gmail.com, lihaiwei.kernel@gmail.com, Yulei Zhang , Xiao Guangrong Subject: Re: [PATCH 01/35] fs: introduce dmemfs module Message-ID: <20201110200411.GU3576660@ZenIV.linux.org.uk> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Oct 08, 2020 at 03:53:51PM +0800, yulei.kernel@gmail.com wrote: > +static struct inode * > +dmemfs_get_inode(struct super_block *sb, const struct inode *dir, umode_t mode, > + dev_t dev); WTF is 'dev' for? > +static int > +dmemfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) > +{ > + struct inode *inode = dmemfs_get_inode(dir->i_sb, dir, mode, dev); > + int error = -ENOSPC; > + > + if (inode) { > + d_instantiate(dentry, inode); > + dget(dentry); /* Extra count - pin the dentry in core */ > + error = 0; > + dir->i_mtime = dir->i_ctime = current_time(inode); > + } > + return error; > +} ... same here, seeing that you only call that thing from the next two functions and you do *not* provide ->mknod() as a method (unsurprisingly - what would device nodes do there?) > +static int dmemfs_create(struct inode *dir, struct dentry *dentry, > + umode_t mode, bool excl) > +{ > + return dmemfs_mknod(dir, dentry, mode | S_IFREG, 0); > +} > + > +static int dmemfs_mkdir(struct inode *dir, struct dentry *dentry, > + umode_t mode) > +{ > + int retval = dmemfs_mknod(dir, dentry, mode | S_IFDIR, 0); > + > + if (!retval) > + inc_nlink(dir); > + return retval; > +} > +int dmemfs_file_mmap(struct file *file, struct vm_area_struct *vma) > +{ > + return 0; > +} > + > +static const struct file_operations dmemfs_file_operations = { > + .mmap = dmemfs_file_mmap, > +}; Er... Is that a placeholder for later in the series? Because as it is, it makes no sense whatsoever - "it can be mmapped, but any access to the mapped area will segfault". > +struct inode *dmemfs_get_inode(struct super_block *sb, > + const struct inode *dir, umode_t mode, dev_t dev) > +{ > + struct inode *inode = new_inode(sb); > + > + if (inode) { > + inode->i_ino = get_next_ino(); > + inode_init_owner(inode, dir, mode); > + inode->i_mapping->a_ops = &empty_aops; > + mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); > + mapping_set_unevictable(inode->i_mapping); > + inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); > + switch (mode & S_IFMT) { > + default: > + init_special_inode(inode, mode, dev); > + break; > + case S_IFREG: > + inode->i_op = &dmemfs_file_inode_operations; > + inode->i_fop = &dmemfs_file_operations; > + break; > + case S_IFDIR: > + inode->i_op = &dmemfs_dir_inode_operations; > + inode->i_fop = &simple_dir_operations; > + > + /* > + * directory inodes start off with i_nlink == 2 > + * (for "." entry) > + */ > + inc_nlink(inode); > + break; > + case S_IFLNK: > + inode->i_op = &page_symlink_inode_operations; > + break; Where would symlinks come from? Or anything other than regular files and directories, for that matter...