Re: [patch] kernel sysfs events layer

Kay Sievers
2004-09-05T02:18:58Z

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On Sat, Sep 04, 2004 at 02:54:33AM +0200, Greg KH wrote:
>
> How about you just add the ability to send hotplug calls across netlink?
> Make it so the kobject_hotplug() function does both the exec() call, and
> a netlink call (based on a config option for those people who like to
> configure such stuff.)
>
> That way, programs who want to listen to netlink messages to get hotplug
> events do so, and so does programs who want to do the /etc/hotplug.d/
> type of notification?
>
> Oh, and attributes. How about we just change kobject_hotplug() to be:
> int kobject_hotplug(const char *action, struct kobject *kobj, struct attribute *attr);
> and if we set attr to be a valid pointer, we make the DEVPATH paramater
> contain the attribute name at the end of it.

If we add this to the kobject_hotplug function, how do we prevent the
execution of /sbin/hotplug for ksets that have positive hotplug filters?
So I've created a new function for now:
int kobj_notify(const char *signal, struct kobject *kobj, struct attribute *attr)

which can be used from the subsystems. This function is also called for
the normal /sbin/hotplug event. (The subsystems may provide a additional
environment for the /sbin/hotplug events, this is ignored by now.)

Here is the debug output of a simple listener, while inserting a
USB-memory-stick, mounting, unmounting and removing it:

[root@pim kdbusd]# ./kdbusd
main: [1094349091] 'add' from '/org/kernel/devices/pci0000:00/0000:00:1d.1/usb3/3-1'
main: [1094349091] 'add' from '/org/kernel/devices/pci0000:00/0000:00:1d.1/usb3/3-1/3-1:1.0'
main: [1094349091] 'add' from '/org/kernel/class/scsi_host/host2'
main: [1094349091] 'add' from '/org/kernel/devices/pci0000:00/0000:00:1d.1/usb3/3-1/3-1:1.0/host2/2:0:0:0'
main: [1094349091] 'add' from '/org/kernel/block/sda'
main: [1094349091] 'add' from '/org/kernel/class/scsi_device/2:0:0:0'
main: [1094349091] 'add' from '/org/kernel/class/scsi_generic/sg0'
main: [1094349092] 'add' from '/org/kernel/block/sda/sda1'

main: [1094349094] 'claim' from '/org/kernel/block/sda/sda1'
main: [1094349101] 'release' from '/org/kernel/block/sda/sda1'

main: [1094349106] 'remove' from '/org/kernel/class/scsi_generic/sg0'
main: [1094349106] 'remove' from '/org/kernel/class/scsi_device/2:0:0:0'
main: [1094349106] 'remove' from '/org/kernel/block/sda/sda1'
main: [1094349106] 'remove' from '/org/kernel/block/sda'
main: [1094349106] 'remove' from '/org/kernel/devices/pci0000:00/0000:00:1d.1/usb3/3-1/3-1:1.0/host2/2:0:0:0'
main: [1094349106] 'remove' from '/org/kernel/class/scsi_host/host2'
main: [1094349106] 'remove' from '/org/kernel/devices/pci0000:00/0000:00:1d.1/usb3/3-1/3-1:1.0'
main: [1094349106] 'remove' from '/org/kernel/devices/pci0000:00/0000:00:1d.1/usb3/3-1'

Thanks,
Kay

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diff -Nru a/fs/super.c b/fs/super.c
--- a/fs/super.c 2004-09-05 03:54:23 +02:00
+++ b/fs/super.c 2004-09-05 03:54:23 +02:00
@@ -35,6 +35,7 @@
#include <linux/vfs.h>
#include <linux/writeback.h> /* for the emergency remount stuff */
#include <linux/idr.h>
+#include <linux/kobj_notify.h>
#include <asm/uaccess.h>

@@ -633,6 +634,16 @@
return (void *)s->s_bdev == data;
}

+static void notify_device_claim(const char *action, struct block_device *bdev)
+{
+ if (bdev->bd_disk) {
+ if (bdev->bd_part)
+ kobj_notify(action, &bdev->bd_part->kobj, NULL);
+ else
+ kobj_notify(action, &bdev->bd_disk->kobj, NULL);
+ }
+}
+
struct super_block *get_sb_bdev(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data,
int (*fill_super)(struct super_block *, void *, int))
@@ -675,8 +686,10 @@
up_write(&s->s_umount);
deactivate_super(s);
s = ERR_PTR(error);
- } else
+ } else {
s->s_flags |= MS_ACTIVE;
+ notify_device_claim("claim", bdev);
+ }
}

return s;
@@ -691,6 +704,8 @@
void kill_block_super(struct super_block *sb)
{
struct block_device *bdev = sb->s_bdev;
+
+ notify_device_claim("release", bdev);
generic_shutdown_super(sb);
set_blocksize(bdev, sb->s_old_blocksize);
close_bdev_excl(bdev);
@@ -717,6 +732,7 @@
return ERR_PTR(error);
}
s->s_flags |= MS_ACTIVE;
+
return s;
}

diff -Nru a/include/linux/kobj_notify.h b/include/linux/kobj_notify.h
--- /dev/null Wed Dec 31 16:00:00 196900
+++ b/include/linux/kobj_notify.h 2004-09-05 03:54:23 +02:00
@@ -0,0 +1,31 @@
+#ifndef _KOBJ_NOTIFY_H_
+#define _KOBJ_NOTIFY_H_
+
+#ifdef __KERNEL__
+#ifdef CONFIG_KOBJ_NOTIFY
+
+extern int kobj_notify(const char *signal, struct kobject *kobj,
+ struct attribute *attr);
+
+extern int kobj_notify_atomic(const char *signal, struct kobject *kobj,
+ struct attribute *attr);
+
+#else
+
+static inline int kobj_notify(const char *signal, struct kobject *kobj,
+ struct attribute *attr)
+{
+ return 0;
+}
+
+static inline int kobj_notify_atomic(const char *signal, struct kobject *kobj,
+ struct attribute *attr)
+{
+ return 0;
+}
+
+
+#endif /* CONFIG_KOBJ_NOTIFY */
+#endif /* __KERNEL__ */
+
+#endif /* _KOBJ_NOTIFY_H_ */
diff -Nru a/include/linux/netlink.h b/include/linux/netlink.h
--- a/include/linux/netlink.h 2004-09-05 03:54:23 +02:00
+++ b/include/linux/netlink.h 2004-09-05 03:54:23 +02:00
@@ -17,6 +17,7 @@
#define NETLINK_ROUTE6 11 /* af_inet6 route comm channel */
#define NETLINK_IP6_FW 13
#define NETLINK_DNRTMSG 14 /* DECnet routing messages */
+#define NETLINK_KOBJ_NOTIFY 15 /* Kernel messages to userspace */
#define NETLINK_TAPBASE 16 /* 16 to 31 are ethertap */

#define MAX_LINKS 32
diff -Nru a/init/Kconfig b/init/Kconfig
--- a/init/Kconfig 2004-09-05 03:54:23 +02:00
+++ b/init/Kconfig 2004-09-05 03:54:23 +02:00
@@ -195,6 +195,21 @@
agent" (/sbin/hotplug) to load modules and set up software needed
to use devices as you hotplug them.

+config KOBJ_NOTIFY
+ bool "Kernel Events Layer"
+ depends on NET && HOTPLUG
+ default y
+ help
+ This option enables the kernel events layer, which is a simple
+ mechanism for kernel-to-user communication over a netlink socket.
+ The goal of the kernel events layer is to provide a simple and
+ efficient events system, that notifies userspace about kobject state
+ changes e.g. hotplug events, power state changes or block device
+ claiming (mount/unmount).
+
+ Say Y, unless you are building a system requiring minimal memory
+ consumption.
+
config IKCONFIG
bool "Kernel .config support"
---help---
diff -Nru a/kernel/Makefile b/kernel/Makefile
--- a/kernel/Makefile 2004-09-05 03:54:23 +02:00
+++ b/kernel/Makefile 2004-09-05 03:54:23 +02:00
@@ -24,6 +24,7 @@
obj-$(CONFIG_AUDIT) += audit.o
obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
obj-$(CONFIG_KPROBES) += kprobes.o
+obj-$(CONFIG_KOBJ_NOTIFY) += kobj_notify.o

ifneq ($(CONFIG_IA64),y)
# According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff -Nru a/kernel/kobj_notify.c b/kernel/kobj_notify.c
--- /dev/null Wed Dec 31 16:00:00 196900
+++ b/kernel/kobj_notify.c 2004-09-05 03:54:23 +02:00
@@ -0,0 +1,88 @@
+/*
+ * kernel/kobj_notify.c - sysfs event delivery via netlink socket
+ *
+ * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2004 Novell, Inc. All rights reserved.
+ *
+ * Licensed under the GNU GPL v2.
+ *
+ * Authors:
+ * Robert Love <rml@novell.com>
+ * Kay Sievers <kay.sievers@vrfy.org>
+ * Arjan van de Ven <arjanv@redhat.com>
+ */
+
+#include <linux/spinlock.h>
+#include <linux/socket.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <linux/string.h>
+#include <linux/kobject.h>
+#include <net/sock.h>
+
+static struct sock *kobj_notify_sock = NULL;
+
+static int do_kobj_notify(const char *signal, struct kobject *kobj,
+ struct attribute *attr, int gfp_mask)
+{
+ const char *path;
+ struct sk_buff *skb;
+ char *buffer;
+ int len;
+
+ if (!kobj_notify_sock)
+ return -EIO;
+
+ path = kobject_get_path(NULL, kobj, gfp_mask);
+ if (!path)
+ return -ENOMEM;
+
+ len = strlen(signal) + 1;
+ len += strlen(path) + 1;
+ if (attr)
+ len += strlen(attr->name) + 1;
+
+ skb = alloc_skb(len, gfp_mask);
+ if (!skb)
+ return -ENOMEM;
+
+ buffer = skb_put(skb, len);
+ if (attr)
+ sprintf(buffer, "%s\n%s/%s", signal, path, attr->name);
+ else
+ sprintf(buffer, "%s\n%s", signal, path);
+ kfree(path);
+
+ return netlink_broadcast(kobj_notify_sock, skb, 0, 1, gfp_mask);
+}
+
+int kobj_notify(const char *signal, struct kobject *kobj,
+ struct attribute *attr)
+{
+ return do_kobj_notify(signal, kobj, attr, GFP_KERNEL);
+}
+
+EXPORT_SYMBOL(kobj_notify);
+
+int kobj_notify_atomic(const char *signal, struct kobject *kobj,
+ struct attribute *attr)
+{
+ return do_kobj_notify(signal, kobj, attr, GFP_ATOMIC);
+}
+
+EXPORT_SYMBOL(kobj_notify_atomic);
+
+static int __init kobj_notify_init(void)
+{
+ kobj_notify_sock = netlink_kernel_create(NETLINK_KOBJ_NOTIFY, NULL);
+
+ if (!kobj_notify_sock) {
+ printk(KERN_ERR
+ "kobj_notify: unable to create netlink socket!\n");
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+core_initcall(kobj_notify_init);
diff -Nru a/lib/kobject.c b/lib/kobject.c
--- a/lib/kobject.c 2004-09-05 03:54:23 +02:00
+++ b/lib/kobject.c 2004-09-05 03:54:23 +02:00
@@ -13,6 +13,7 @@
#undef DEBUG

#include <linux/kobject.h>
+#include <linux/kobj_notify.h>
#include <linux/string.h>
#include <linux/module.h>
#include <linux/stat.h>
@@ -202,6 +203,8 @@
goto exit;
}
}
+
+ kobj_notify(action, kobj, NULL);

pr_debug ("%s: %s %s %s %s %s %s %s\n", __FUNCTION__, argv[0], argv[1],
envp[0], envp[1], envp[2], envp[3], envp[4]);