SYSFS: Allow boot time switching between deprecated and modern sysfs layout

I have some systems which need legacy sysfs due to old tools that are
making assumptions that a directory can never be a symlink to another
directory, and it's a big hazzle to compile separate kernels for them.

This patch turns CONFIG_SYSFS_DEPRECATED into a run time option
that can be switched on/off the kernel command line. This way
the same binary can be used in both cases with just a option
on the command line.

The old CONFIG_SYSFS_DEPRECATED_V2 option is still there to set
the default. I kept the weird name to not break existing
config files.

Also the compat code can be still completely disabled by undefining
CONFIG_SYSFS_DEPRECATED_SWITCH -- just the optimizer takes
care of this now instead of lots of ifdefs. This makes the code
look nicer.

v2: This is an updated version on top of Kay's patch to only
handle the block devices. I tested it on my old systems
and that seems to work.

Cc: axboe@kernel.dk
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Andi Kleen 2010-09-08 16:54:17 +02:00 committed by Greg Kroah-Hartman
parent 39aba963d9
commit e52eec13cd
7 changed files with 68 additions and 30 deletions

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@ -2365,6 +2365,15 @@ and is between 256 and 4096 characters. It is defined in the file
switches= [HW,M68k]
sysfs.deprecated=0|1 [KNL]
Enable/disable old style sysfs layout for old udev
on older distributions. When this option is enabled
very new udev will not work anymore. When this option
is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
in older udev will not work anymore.
Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
the kernel configuration.
sysrq_always_enabled
[KNL]
Ignore sysrq setting - this boot parameter will

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@ -22,9 +22,7 @@
#include "blk.h"
static DEFINE_MUTEX(block_class_lock);
#ifndef CONFIG_SYSFS_DEPRECATED
struct kobject *block_depr;
#endif
/* for extended dynamic devt allocation, currently only one major is used */
#define MAX_EXT_DEVT (1 << MINORBITS)
@ -803,10 +801,9 @@ static int __init genhd_device_init(void)
register_blkdev(BLOCK_EXT_MAJOR, "blkext");
#ifndef CONFIG_SYSFS_DEPRECATED
/* create top-level block dir */
block_depr = kobject_create_and_add("block", NULL);
#endif
if (!sysfs_deprecated)
block_depr = kobject_create_and_add("block", NULL);
return 0;
}

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@ -184,9 +184,9 @@ int __class_register(struct class *cls, struct lock_class_key *key)
if (!cls->dev_kobj)
cls->dev_kobj = sysfs_dev_char_kobj;
#if defined(CONFIG_SYSFS_DEPRECATED) && defined(CONFIG_BLOCK)
#if defined(CONFIG_BLOCK)
/* let the block class directory show up in the root of sysfs */
if (cls != &block_class)
if (!sysfs_deprecated || cls != &block_class)
cp->class_subsys.kobj.kset = class_kset;
#else
cp->class_subsys.kobj.kset = class_kset;

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@ -26,6 +26,19 @@
#include "base.h"
#include "power/power.h"
#ifdef CONFIG_SYSFS_DEPRECATED
#ifdef CONFIG_SYSFS_DEPRECATED_V2
long sysfs_deprecated = 1;
#else
long sysfs_deprecated = 0;
#endif
static __init int sysfs_deprecated_setup(char *arg)
{
return strict_strtol(arg, 10, &sysfs_deprecated);
}
early_param("sysfs.deprecated", sysfs_deprecated_setup);
#endif
int (*platform_notify)(struct device *dev) = NULL;
int (*platform_notify_remove)(struct device *dev) = NULL;
static struct kobject *dev_kobj;
@ -617,14 +630,13 @@ static struct kobject *get_device_parent(struct device *dev,
struct kobject *parent_kobj;
struct kobject *k;
#ifdef CONFIG_SYSFS_DEPRECATED
/* block disks show up in /sys/block */
if (dev->class == &block_class) {
if (sysfs_deprecated && dev->class == &block_class) {
if (parent && parent->class == &block_class)
return &parent->kobj;
return &block_class.p->class_subsys.kobj;
}
#endif
/*
* If we have no parent, we live in "virtual".
* Class-devices with a non class-device as parent, live
@ -707,11 +719,9 @@ static int device_add_class_symlinks(struct device *dev)
goto out_subsys;
}
#ifdef CONFIG_SYSFS_DEPRECATED
/* /sys/block has directories and does not need symlinks */
if (dev->class == &block_class)
if (sysfs_deprecated && dev->class == &block_class)
return 0;
#endif
/* link in the class directory pointing to the device */
error = sysfs_create_link(&dev->class->p->class_subsys.kobj,
@ -738,10 +748,8 @@ static void device_remove_class_symlinks(struct device *dev)
if (dev->parent && device_is_not_partition(dev))
sysfs_remove_link(&dev->kobj, "device");
sysfs_remove_link(&dev->kobj, "subsystem");
#ifdef CONFIG_SYSFS_DEPRECATED
if (dev->class == &block_class)
if (sysfs_deprecated && dev->class == &block_class)
return;
#endif
sysfs_delete_link(&dev->class->p->class_subsys.kobj, &dev->kobj, dev_name(dev));
}

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@ -513,14 +513,14 @@ void register_disk(struct gendisk *disk)
if (device_add(ddev))
return;
#ifndef CONFIG_SYSFS_DEPRECATED
err = sysfs_create_link(block_depr, &ddev->kobj,
kobject_name(&ddev->kobj));
if (err) {
device_del(ddev);
return;
if (!sysfs_deprecated) {
err = sysfs_create_link(block_depr, &ddev->kobj,
kobject_name(&ddev->kobj));
if (err) {
device_del(ddev);
return;
}
}
#endif
disk->part0.holder_dir = kobject_create_and_add("holders", &ddev->kobj);
disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);
@ -737,8 +737,7 @@ void del_gendisk(struct gendisk *disk)
kobject_put(disk->part0.holder_dir);
kobject_put(disk->slave_dir);
disk->driverfs_dev = NULL;
#ifndef CONFIG_SYSFS_DEPRECATED
sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
#endif
if (!sysfs_deprecated)
sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
device_del(disk_to_dev(disk));
}

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@ -751,4 +751,11 @@ do { \
MODULE_ALIAS("char-major-" __stringify(major) "-" __stringify(minor))
#define MODULE_ALIAS_CHARDEV_MAJOR(major) \
MODULE_ALIAS("char-major-" __stringify(major) "-*")
#ifdef CONFIG_SYSFS_DEPRECATED
extern long sysfs_deprecated;
#else
#define sysfs_deprecated 0
#endif
#endif /* _DEVICE_H_ */

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@ -660,8 +660,12 @@ config SYSFS_DEPRECATED
depends on SYSFS
default n
help
This option switches the layout of the "block" class devices, to not
show up in /sys/class/block/, but only in /sys/block/.
This option adds code that switches the layout of the "block" class
devices, to not show up in /sys/class/block/, but only in
/sys/block/.
This switch is only active when the sysfs.deprecated=1 boot option is
passed or the SYSFS_DEPRECATED_V2 option is set.
This option allows new kernels to run on old distributions and tools,
which might get confused by /sys/class/block/. Since 2007/2008 all
@ -672,8 +676,22 @@ config SYSFS_DEPRECATED
option enabled.
Only if you are using a new kernel on an old distribution, you might
need to say Y here. Never say Y, if the original kernel, that came
with your distribution, has not set this option.
need to say Y here.
config SYSFS_DEPRECATED_V2
bool "enabled deprecated sysfs features by default"
default n
depends on SYSFS
depends on SYSFS_DEPRECATED
help
Enable deprecated sysfs by default.
See the CONFIG_SYSFS_DEPRECATED option for more details about this
option.
Only if you are using a new kernel on an old distribution, you might
need to say Y here. Even then, odds are you would not need it
enabled, you can always pass the boot option if absolutely necessary.
config RELAY
bool "Kernel->user space relay support (formerly relayfs)"