linux-kernel - Re: [PATCH 01/35] fs: introduce dmemfs module

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Message-ID: <20201111230908.GC3576660@ZenIV.linux.org.uk>
Date:   Wed, 11 Nov 2020 23:09:08 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     yulei zhang <yulei.kernel@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Haiwei Li <lihaiwei.kernel@...il.com>,
        Yulei Zhang <yuleixzhang@...cent.com>,
        Xiao Guangrong <gloryxiao@...cent.com>
Subject: Re: [PATCH 01/35] fs: introduce dmemfs module

On Wed, Nov 11, 2020 at 04:53:00PM +0800, yulei zhang wrote:

> > ... 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?)
> >
> 
> Thanks for pointing this out. we may need support the mknod method, otherwise
> the dev is redundant  and need to be removed.

I'd suggest turning that into (static) __create_file(....) with

static int dmemfs_create(struct inode *dir, struct dentry *dentry,
			 umode_t mode, bool excl)
{
	return __create_file(dir, dentry, mode | S_IFREG);
}

static int dmemfs_mkdir(struct inode *dir, struct dentry *dentry,
			 umode_t mode)
{
	return __create_file(dir, dentry, mode | S_IFDIR);
}

(i.e. even inc_nlink() of parent folded into that).

[snip]

> Yes, we seperate the full implementation for dmemfs_file_mmap into
> patch 05/35, it
> will assign the interfaces to handle the page fault.

It would be less confusing to move the introduction of ->mmap() to that patch,
then.