linux-kernel - Re: [RFC PATCH 09/20] famfs: Add super

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Message-ID: <z3tnfxbbvhtbyantbm3yr3yv2qsih7darbm3p5pwwdsknuxlqa@rvexwleaixiy>
Date: Mon, 26 Feb 2024 15:47:53 -0600
From: John Groves <John@...ves.net>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: John Groves <jgroves@...ron.com>, Jonathan Corbet <corbet@....net>, 
	Dan Williams <dan.j.williams@...el.com>, Vishal Verma <vishal.l.verma@...el.com>, 
	Dave Jiang <dave.jiang@...el.com>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, Matthew Wilcox <willy@...radead.org>, 
	linux-cxl@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev, john@...alactic.com, 
	Dave Chinner <david@...morbit.com>, Christoph Hellwig <hch@...radead.org>, 
	dave.hansen@...ux.intel.com, gregory.price@...verge.com
Subject: Re: [RFC PATCH 09/20] famfs: Add super_operations

On 24/02/26 12:51PM, Jonathan Cameron wrote:
> On Fri, 23 Feb 2024 11:41:53 -0600
> John Groves <John@...ves.net> wrote:
> 
> > Introduce the famfs superblock operations
> > 
> > Signed-off-by: John Groves <john@...ves.net>
> > ---
> >  fs/famfs/famfs_inode.c | 72 ++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 72 insertions(+)
> >  create mode 100644 fs/famfs/famfs_inode.c
> > 
> > diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c
> > new file mode 100644
> > index 000000000000..3329aff000d1
> > --- /dev/null
> > +++ b/fs/famfs/famfs_inode.c
> > @@ -0,0 +1,72 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * famfs - dax file system for shared fabric-attached memory
> > + *
> > + * Copyright 2023-2024 Micron Technology, inc
> > + *
> > + * This file system, originally based on ramfs the dax support from xfs,
> > + * is intended to allow multiple host systems to mount a common file system
> > + * view of dax files that map to shared memory.
> > + */
> > +
> > +#include <linux/fs.h>
> > +#include <linux/pagemap.h>
> > +#include <linux/highmem.h>
> > +#include <linux/time.h>
> > +#include <linux/init.h>
> > +#include <linux/string.h>
> > +#include <linux/backing-dev.h>
> > +#include <linux/sched.h>
> > +#include <linux/parser.h>
> > +#include <linux/magic.h>
> > +#include <linux/slab.h>
> > +#include <linux/uaccess.h>
> > +#include <linux/fs_context.h>
> > +#include <linux/fs_parser.h>
> > +#include <linux/seq_file.h>
> > +#include <linux/dax.h>
> > +#include <linux/hugetlb.h>
> > +#include <linux/uio.h>
> > +#include <linux/iomap.h>
> > +#include <linux/path.h>
> > +#include <linux/namei.h>
> > +#include <linux/pfn_t.h>
> > +#include <linux/blkdev.h>
> 
> That's a lot of header for such a small patch.. I'm going to guess
> they aren't all used - bring them in as you need them - I hope
> you never need some of these!

I didn't phase in headers in this series. Based on these recommendations,
the next version of this series is gonna have to be 100% constructed from
scratch, but okay. My head hurts just thinking about it. I need a nap...

I've been rebasing for 3 weeks to get this series out, and it occurs to
me that maybe there are tools I'm not aware of that make it eaiser? I'm
just typing "rebase -i..." 200 times a day. Is there a less soul-crushing way?

> 
> 
> > +
> > +#include "famfs_internal.h"
> > +
> > +#define FAMFS_DEFAULT_MODE	0755
> > +
> > +static const struct super_operations famfs_ops;
> > +static const struct inode_operations famfs_file_inode_operations;
> > +static const struct inode_operations famfs_dir_inode_operations;
> 
> Why are these all up here?

These forward declarations are needed by a later patch in the series.
They were in famfs_internal.h, but they are only used in this file, so
I moved them here.

For all answers such as this, I will hereafter reply "rebase fu", with
further clarification only if necessary.

> 
> > +
> > +/**********************************************************************************
> > + * famfs super_operations
> > + *
> > + * TODO: implement a famfs_statfs() that shows size, free and available space, etc.
> > + */
> > +
> > +/**
> > + * famfs_show_options() - Display the mount options in /proc/mounts.
> Run kernel doc script + fix all warnings.

Will do; I actually think I have already fixed those...

> 
> > + */
> > +static int famfs_show_options(
> > +	struct seq_file *m,
> > +	struct dentry   *root)
> Not that familiar with fs code, but this unusual kernel style. I'd go with 
> something more common
> 
> static int famfs_show_options(struct seq_file *m, struct dentry *root)

Done. To all functions...

> 
> > +{
> > +	struct famfs_fs_info *fsi = root->d_sb->s_fs_info;
> > +
> > +	if (fsi->mount_opts.mode != FAMFS_DEFAULT_MODE)
> > +		seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct super_operations famfs_ops = {
> > +	.statfs		= simple_statfs,
> > +	.drop_inode	= generic_delete_inode,
> > +	.show_options	= famfs_show_options,
> > +};
> > +
> > +
> One blank line probably fine.

Done

> 
> 
> Add the rest of the stuff a module normally has, author etc in this
> patch.

Because "rebase fu" I'm not sure the order will remain the same. Will
try not to make anybody tell me this again though...

John