Re: [RFC PATCH 07/20] famfs: Add include/linux/famfs_ioctl.h

John Groves
2024-02-24T02:23:25Z

On 24/02/23 05:39PM, Randy Dunlap wrote:
> Hi--
>
> On 2/23/24 09:41, John Groves wrote:
> > Add uapi include file for famfs. The famfs user space uses ioctl on
> > individual files to pass in mapping information and file size. This
> > would be hard to do via sysfs or other means, since it's
> > file-specific.
> >
> > Signed-off-by: John Groves <john@groves.net>
> > ---
> > include/uapi/linux/famfs_ioctl.h | 56 ++++++++++++++++++++++++++++++++
> > 1 file changed, 56 insertions(+)
> > create mode 100644 include/uapi/linux/famfs_ioctl.h
> >
> > diff --git a/include/uapi/linux/famfs_ioctl.h b/include/uapi/linux/famfs_ioctl.h
> > new file mode 100644
> > index 000000000000..6b3e6452d02f
> > --- /dev/null
> > +++ b/include/uapi/linux/famfs_ioctl.h
> > @@ -0,0 +1,56 @@
> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > +/*
> > + * 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,
>
> This is confusing to me. Is it just me? ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Thanks Randy. I think I was trying to say "based on ramfs *plus* the dax
support from xfs. But I'll try to come up with something more clear than
that...

>
> > + * is intended to allow multiple host systems to mount a common file system
> > + * view of dax files that map to shared memory.
> > + */
> > +#ifndef FAMFS_IOCTL_H
> > +#define FAMFS_IOCTL_H
> > +
> > +#include <linux/ioctl.h>
> > +#include <linux/uuid.h>
> > +
> > +#define FAMFS_MAX_EXTENTS 2
> > +
> > +enum extent_type {
> > + SIMPLE_DAX_EXTENT = 13,
> > + INVALID_EXTENT_TYPE,
> > +};
> > +
> > +struct famfs_extent {
> > + __u64 offset;
> > + __u64 len;
> > +};
> > +
> > +enum famfs_file_type {
> > + FAMFS_REG,
> > + FAMFS_SUPERBLOCK,
> > + FAMFS_LOG,
> > +};
> > +
> > +/**
>
> "/**" is used to begin kernel-doc comments, but this comment block is missing
> a few entries to make it be kernel-doc compatible. Please either add them
> or just use "/*" to begin the comment.

Will do, thanks. And I'll check the whole code base for other instances;
I won't be surprise if I was sloop about that in more than one place.

>
> > + * struct famfs_ioc_map
> > + *
> > + * This is the metadata that indicates where the memory is for a famfs file
> > + */
> > +struct famfs_ioc_map {
> > + enum extent_type extent_type;
> > + enum famfs_file_type file_type;
> > + __u64 file_size;
> > + __u64 ext_list_count;
> > + struct famfs_extent ext_list[FAMFS_MAX_EXTENTS];
> > +};
> > +
> > +#define FAMFSIOC_MAGIC 'u'
>
> This 'u' value should be documented in
> Documentation/userspace-api/ioctl/ioctl-number.rst.
>
> and if possible, you might want to use values like 0x5x or 0x8x
> that don't conflict with the ioctl numbers that are already used
> in the 'u' space.

Will do. I was trying to be too clever there, invoking "mu" for
micron.

>
> > +
> > +/* famfs file ioctl opcodes */
> > +#define FAMFSIOC_MAP_CREATE _IOW(FAMFSIOC_MAGIC, 1, struct famfs_ioc_map)
> > +#define FAMFSIOC_MAP_GET _IOR(FAMFSIOC_MAGIC, 2, struct famfs_ioc_map)
> > +#define FAMFSIOC_MAP_GETEXT _IOR(FAMFSIOC_MAGIC, 3, struct famfs_extent)
> > +#define FAMFSIOC_NOP _IO(FAMFSIOC_MAGIC, 4)
> > +
> > +#endif /* FAMFS_IOCTL_H */
>
> --
> #Randy

Thank you for taking the time to look it over, Randy.

John