linux-kernel - Re: [RFC PATCH 14/20] famfs: Add struct file

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Date: Mon, 26 Feb 2024 13:32:37 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: John Groves <John@...ves.net>
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 14/20] famfs: Add struct file_operations

On Fri, 23 Feb 2024 11:41:58 -0600
John Groves <John@...ves.net> wrote:

> This commit introduces the famfs file_operations. We call
> thp_get_unmapped_area() to force PMD page alignment. Our read and
> write handlers (famfs_dax_read_iter() and famfs_dax_write_iter())
> call dax_iomap_rw() to do the work.
> 
> famfs_file_invalid() checks for various ways a famfs file can be
> in an invalid state so we can fail I/O or fault resolution in those
> cases. Those cases include the following:
> 
> * No famfs metadata
> * file i_size does not match the originally allocated size
> * file is not flagged as DAX
> * errors were detected previously on the file
> 
> An invalid file can often be fixed by replaying the log, or by
> umount/mount/log replay - all of which are user space operations.
> 
> Signed-off-by: John Groves <john@...ves.net>
> ---
>  fs/famfs/famfs_file.c | 136 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 136 insertions(+)
> 
> diff --git a/fs/famfs/famfs_file.c b/fs/famfs/famfs_file.c
> index fc667d5f7be8..5228e9de1e3b 100644
> --- a/fs/famfs/famfs_file.c
> +++ b/fs/famfs/famfs_file.c
> @@ -19,6 +19,142 @@
>  #include <uapi/linux/famfs_ioctl.h>
>  #include "famfs_internal.h"
>  
> +/*********************************************************************
> + * file_operations
> + */
> +
> +/* Reject I/O to files that aren't in a valid state */
> +static ssize_t
> +famfs_file_invalid(struct inode *inode)
> +{
> +	size_t i_size       = i_size_read(inode);
> +	struct famfs_file_meta *meta = inode->i_private;
> +
> +	if (!meta) {
> +		pr_err("%s: un-initialized famfs file\n", __func__);
> +		return -EIO;
> +	}
> +	if (i_size != meta->file_size) {
> +		pr_err("%s: something changed the size from  %ld to %ld\n",
> +		       __func__, meta->file_size, i_size);
> +		meta->error = 1;
> +		return -ENXIO;
> +	}
> +	if (!IS_DAX(inode)) {
> +		pr_err("%s: inode %llx IS_DAX is false\n", __func__, (u64)inode);
> +		meta->error = 1;
> +		return -ENXIO;
> +	}
> +	if (meta->error) {
> +		pr_err("%s: previously detected metadata errors\n", __func__);
> +		meta->error = 1;

Already set?  If treating it as only a boolean, maybe make it one?

> +		return -EIO;
> +	}
> +	return 0;
> +}