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

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Date: Mon, 26 Feb 2024 17:09:36 -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 14/20] famfs: Add struct file_operations

On 24/02/26 01:32PM, Jonathan Cameron wrote:
> 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?

Done, thanks

John