Re: [ PATCH 2.6.16-rc3-xen 3/3] sysfs: export Xen hypervisor attributes to sysfs

Greg KH
2006-02-21T18:35:23Z

No full description explaining why you need this?

No "Signed-off-by:"?

On Tue, Feb 21, 2006 at 09:40:02AM -0500, Mike D. Day wrote:
> # HG changeset patch
> # User mdday@dual.silverwood.home
> # Node ID 10c66e0408d1b22db15b8943223f1b6d7713422d
> # Parent f5f32dc60121c32fab158a814c914aae3b77ba06
> Module that exports Xen Hypervisor attributes to /sys/hypervisor.
>
> signed-off-by: Mike D. Day <ncmike@us.ibm.com>
>
> diff -r f5f32dc60121 -r 10c66e0408d1
> linux-2.6-xen-sparse/drivers/xen/core/Makefile
> --- a/linux-2.6-xen-sparse/drivers/xen/core/Makefile Tue Feb 21 08:12:11
> 2006 -0500

Linewrapped :(

> +++ b/linux-2.6-xen-sparse/drivers/xen/core/Makefile Tue Feb 21 08:13:00
> 2006 -0500
> @@ -7,3 +7,4 @@ obj-$(CONFIG_PROC_FS) += xen_proc.o
> obj-$(CONFIG_PROC_FS) += xen_proc.o
> obj-$(CONFIG_NET) += skbuff.o
> obj-$(CONFIG_SMP) += smpboot.o
> +obj-$(CONFIG_XEN_SYSFS) += xen_sysfs.o

leading spaces eaten by your email client. It looks like it was hungry
this morning...

> diff -r f5f32dc60121 -r 10c66e0408d1
> linux-2.6-xen-sparse/drivers/xen/core/xen_sysfs.c
> --- /dev/null Thu Jan 1 00:00:00 1970 +0000
> +++ b/linux-2.6-xen-sparse/drivers/xen/core/xen_sysfs.c Tue Feb 21
> 08:13:00 2006 -0500
> @@ -0,0 +1,411 @@
> +#include <linux/config.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/kobject.h>
> +#include <linux/sysfs.h>
> +
> +#include <xen/xen_sysfs.h>
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Mike D. Day <ncmike@us.ibm.com>");
> +
> +decl_subsys(hypervisor, NULL, NULL);

This should go into a separate file, along with it's registration, so
that other hypervisors can have access to it, right?

> +struct kset xen_kset = {
> + .subsys = &hypervisor_subsys,
> + .kobj = {
> + .name = "xen",
> + },
> +};

I thought I asked you last time to not create a "bare" kset. Any reason
why you didn't like that suggestion?

> +static struct sysfs_ops xen_ops = {
> +
> + .show = xen_show,
> +};

You will _never_ have a store attribute for xen? And why are you
passing the attribute field to your show function if you never use it?

> +/* xen version attributes */
> +
> +static ssize_t major_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + int version = HYPERVISOR_xen_version(XENVER_version, NULL);
> + if (version)
> + return sprintf(page, "%d\n", version >> 16);
> + return 0;
> +}

Shouldn't you return an error if you could not get the version?
Otherwise your userspace tools will not know something is wrong.

You do this for all of your show attributes...

> +static ssize_t extra_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + char extra_ver[XENVER_EXTRAVERSION_LEN];
> + int err = HYPERVISOR_xen_version(XENVER_extraversion, extra_ver);
> + if (0 == err)
> + return sprintf(page, "%s\n", extra_ver);
> + return 0;
> +}

What's with the (0 == err)? You don't do that above in the other
functions, so please be consistant. Putting a value on the left side is
not normal kernel coding style.

> +static struct kobject * v_kobj;
> +
> +int __init
> +xen_version_init(void)
> +{
> + int err = -ENOMEM;
> + v_kobj = kcalloc(sizeof(struct kobject), sizeof(char), GFP_KERNEL);

kzalloc please.

> + if (v_kobj) {
> + kobject_set_name(v_kobj, "version");
> + v_kobj->ktype = &xen_version_type;
> + kobject_init(v_kobj);
> + v_kobj->dentry = xen_kset.kobj.dentry;
> + err = sysfs_create_group(v_kobj, &version_group);
> + }
> + return err;
> +}
> +
> +
> +static ssize_t compiler_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + int err = 0;
> + struct xen_compile_info * info =
> + kmalloc(sizeof(struct xen_compile_info), GFP_KERNEL);
> + if (info ) {
> + if (0 == HYPERVISOR_xen_version(XENVER_compile_info, info))
> + err = sprintf(page, "%s\n", info->compiler);

Hey, look a different way to check the return value... Are you sure only
1 person wrote this file, and not 3 different authors? :)

> + kfree(info);
> + }
> + return err;
> +}
> +

> +static struct attribute_group xen_compilation_group = {
> + .name = "compilation",
> + .attrs = xen_compile_attrs,
> +};
> +

Trailing whitespace. This is also in other parts of the patch, please
do not do that.

> +static struct kobj_type xen_compilation_type = {
> + .release = kobj_release,
> + .sysfs_ops = &xen_ops,
> + .default_attrs = xen_compile_attrs,
> +};
> +
> +static struct kobject * c_kobj;

I'm all for descriptive variable names, but unfortunatly, this does not
qualify...

> +int __init
> +static xen_compilation_init(void)
> +{
> + int err = -ENOMEM;
> + c_kobj = kcalloc(sizeof(struct kobject), sizeof(char), GFP_KERNEL);
> + if (c_kobj) {
> + kobject_set_name(c_kobj, "compilation");
> + c_kobj->ktype = &xen_compilation_type;
> + kobject_init(c_kobj);
> + c_kobj->dentry = xen_kset.kobj.dentry;
> + err = sysfs_create_group(c_kobj, &xen_compilation_group);
> + }
> + return err;
> +}

No, just name the attribute group. Then you don't have to create a
kobject at all. Same goes for all of the different attribute groups...

> +
> +static void xen_compilation_destroy(void)
> +{
> + sysfs_remove_group(c_kobj, &xen_compilation_group);
> + kobject_put(c_kobj);
> + return;
> +}
> +
> +
> +/* xen properties info */
> +
> +static ssize_t capabilities_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + int err = 0;
> + char * caps = kmalloc(XENVER_CAPABILITIES_INFO_LEN, GFP_KERNEL);
> + if (caps) {
> + if (0 == HYPERVISOR_xen_version(XENVER_capabilities, caps))
> + err = sprintf(page, "%s\n", caps);
> + kfree(caps);
> + }
> + return err;
> +}
> +
> +static struct xen_attr xen_capable = __ATTR_RO(capabilities);
> +
> +static ssize_t changeset_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + int err = 0;
> + char * cset = kmalloc(XENVER_CSET_INFO_LEN, GFP_KERNEL);
> + if (cset) {
> + if (0 == HYPERVISOR_xen_version(XENVER_changeset, cset))
> + err = sprintf(page, "%s\n", cset);
> + kfree(cset);
> + }
> + return err;
> +}
> +
> +static struct xen_attr xen_cset = __ATTR_RO(changeset);
> +
> +static ssize_t virt_start_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + int err = 0;
> + struct xen_platform_parameters * parms =
> + kmalloc(sizeof(struct xen_platform_parameters), GFP_KERNEL);
> + if (parms) {
> + if (0 == HYPERVISOR_xen_version(XENVER_platform_parameters,
> + parms))
> + err = sprintf(page, "%lx\n", parms->virt_start);
> + kfree(parms);
> + }
> + return err;
> +}
> +
> +static struct xen_attr xen_virt_start = __ATTR_RO(virt_start);
> +
> +
> +static ssize_t writable_pt_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + int err = 0;
> + struct xen_feature_info * info =
> + kmalloc(sizeof(struct xen_feature_info), GFP_KERNEL);
> + if (info) {
> + info->submap_idx = XENFEAT_writable_page_tables;
> + if (0 == HYPERVISOR_xen_version(XENVER_get_features, info))
> + err = sprintf(page, "%d\n", info->submap);
> + kfree(info);
> + }
> + return err;
> +}
> +
> +static struct xen_attr xen_wpt = __ATTR_RO(writable_pt);
> +
> +static ssize_t writable_dt_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + int err = 0;
> + struct xen_feature_info * info =
> + kmalloc(sizeof(struct xen_feature_info), GFP_KERNEL);
> + if (info) {
> + info->submap_idx = XENFEAT_writable_descriptor_tables;
> + if (0 == HYPERVISOR_xen_version(XENVER_get_features, info))
> + err = sprintf(page, "%d\n", info->submap);
> + kfree(info);
> + }
> + return err;
> +}
> +
> +static struct xen_attr xen_wdt = __ATTR_RO(writable_dt);
> +
> +static ssize_t translated_pm_show(struct kobject * kobj,
> + struct attribute * attr,
> + char * page)
> +{
> + int err = 0;
> + struct xen_feature_info * info =
> + kmalloc(sizeof(struct xen_feature_info), GFP_KERNEL);
> + if (info) {
> + info->submap_idx = XENFEAT_auto_translated_physmap;
> + if (0 == HYPERVISOR_xen_version(XENVER_get_features, info))
> + err = sprintf(page, "%d\n", info->submap);
> + kfree(info);
> + }
> + return err;
> +}
> +
> +static struct xen_attr xen_atp = __ATTR_RO(translated_pm);
> +
> +static struct attribute * xen_properties_attrs[] = {
> + &xen_capable.attr,
> + &xen_cset.attr,
> + &xen_virt_start.attr,
> + &xen_wpt.attr,
> + &xen_wdt.attr,
> + &xen_atp.attr,
> + NULL
> +};
> +
> +static struct attribute_group xen_properties_group = {
> + .name = "properties",
> + .attrs = xen_properties_attrs,
> +};
> +
> +static struct kobj_type xen_properties_type = {
> + .release = kobj_release,
> + .sysfs_ops = &xen_ops,
> + .default_attrs = xen_properties_attrs,
> +};
> +
> +static struct kobject * p_kobj;
> +
> +static int __init
> +xen_properties_init(void)
> +{
> + int err = -ENOMEM;
> + p_kobj = kcalloc(sizeof(struct kobject), sizeof(char), GFP_KERNEL);
> + if (p_kobj) {
> + kobject_set_name(p_kobj, "properties");
> + p_kobj->ktype = &xen_properties_type;
> + kobject_init(p_kobj);
> + p_kobj->dentry = xen_kset.kobj.dentry;
> + err = sysfs_create_group(p_kobj, &xen_properties_group);
> + }
> + return err;
> +}
> +
> +static void xen_properties_destroy(void)
> +{
> + sysfs_remove_group(p_kobj, &xen_properties_group);
> + kobject_put(p_kobj);
> +}
> +
> +
> +static int __init
> +hyper_sysfs_init(void)
> +{
> + __label__ out;

What is "__label__"?

> +
> + int err = subsystem_register(&hypervisor_subsys);
> + if (err)
> + goto out;
> + err = kset_register(&xen_kset);
> + if (err)
> + goto out;
> + err = xen_version_init();
> + if (err)
> + goto out;
> + err = xen_compilation_init();
> + if (err)
> + goto out;
> + err = xen_properties_init();
> +
> +out:
> + return err;

If you have an error, you do not back out the registration of any of the
other attributes. So, why have any error handling at all?

> +static void hyper_sysfs_exit(void)
> +{
> + xen_properties_destroy();
> + xen_compilation_destroy();
> + xen_version_destroy();
> + kset_unregister(&xen_kset);
> + subsystem_unregister(&hypervisor_subsys);
> +}
> +
> +
> +module_init(hyper_sysfs_init);
> +module_exit(hyper_sysfs_exit);
> +
> diff -r f5f32dc60121 -r 10c66e0408d1
> linux-2.6-xen-sparse/include/xen/xen_sysfs.h
> --- /dev/null Thu Jan 1 00:00:00 1970 +0000
> +++ b/linux-2.6-xen-sparse/include/xen/xen_sysfs.h Tue Feb 21 08:13:00
> 2006 -0500
> @@ -0,0 +1,30 @@
> +/*
> + copyright (c) 2006 IBM Corporation
> + Authored by: Mike D. Day <ncmike@us.ibm.com>
> +
> + This program is free software; you can redistribute it and/or modify
> + it under the terms of the GNU General Public License version 2 as
> + published by the Free Software Foundation.
> +*/
> +
> +
> +
> +#ifndef _XEN_SYSFS_H_
> +#define _XEN_SYSFS_H_
> +
> +#include <linux/kobject.h>
> +#include <linux/sysfs.h>
> +#include <linux/module.h>
> +#include <asm/hypercall.h>
> +#include <xen/interface/version.h>

Why does this header file depend on the module, hypercall and version
header files?

> +
> +
> +struct xen_attr {
> + struct attribute attr;
> + ssize_t (*show)(struct kobject *, struct attribute *, char *);
> + ssize_t (*store)(struct kobject *, struct attribute *, char *);
> +};

Why export this structure?
Why even have this header file at all?

> +
> +extern int HYPERVISOR_xen_version(int, void*);

You don't have this in some xen header file? Shouldn't it go next to
all of the other HYPERVISOR calls?

Care to try again?

thanks,

greg k-h