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>

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>
Andi Kleen · Greg Kroah-Hartman
1 parent 39aba963d9
Showing 7 changed files with 68 additions and 30 deletions Side-by-side Diff
Documentation/kernel-parameters.txt
block/genhd.c
drivers/base/class.c
drivers/base/core.c
fs/partitions/check.c
include/linux/device.h
init/Kconfig
@@ -2365,6 +2365,15 @@
  
 	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
@@ -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 @@
  
 	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;
 }
  
@@ -184,9 +184,9 @@
 	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;
@@ -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 @@
 		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 @@
 			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 @@
 	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));
 }
  
@@ -513,14 +513,14 @@
  
 	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);
  
@@ -737,9 +737,8 @@
 	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));
 }
@@ -751,5 +751,12 @@
 	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_ */
@@ -660,9 +660,13 @@
 	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
 	  major distributions and tools handle this just fine.
@@ -672,8 +676,22 @@
 	  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)"
...	...	@@ -2365,6 +2365,15 @@
2365	2365
2366	2366	switches= [HW,M68k]
2367	2367
	2368	+ sysfs.deprecated=0\|1 [KNL]
	2369	+ Enable/disable old style sysfs layout for old udev
	2370	+ on older distributions. When this option is enabled
	2371	+ very new udev will not work anymore. When this option
	2372	+ is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
	2373	+ in older udev will not work anymore.
	2374	+ Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
	2375	+ the kernel configuration.
	2376	+
2368	2377	sysrq_always_enabled
2369	2378	[KNL]
2370	2379	Ignore sysrq setting - this boot parameter will
...	...	@@ -22,9 +22,7 @@
22	22	#include "blk.h"
23	23
24	24	static DEFINE_MUTEX(block_class_lock);
25		-#ifndef CONFIG_SYSFS_DEPRECATED
26	25	struct kobject *block_depr;
27		-#endif
28	26
29	27	/* for extended dynamic devt allocation, currently only one major is used */
30	28	#define MAX_EXT_DEVT (1 << MINORBITS)
31	29
...	...	@@ -803,10 +801,9 @@
803	801
804	802	register_blkdev(BLOCK_EXT_MAJOR, "blkext");
805	803
806		-#ifndef CONFIG_SYSFS_DEPRECATED
807	804	/* create top-level block dir */
808		- block_depr = kobject_create_and_add("block", NULL);
809		-#endif
	805	+ if (!sysfs_deprecated)
	806	+ block_depr = kobject_create_and_add("block", NULL);
810	807	return 0;
811	808	}
812	809
...	...	@@ -184,9 +184,9 @@
184	184	if (!cls->dev_kobj)
185	185	cls->dev_kobj = sysfs_dev_char_kobj;
186	186
187		-#if defined(CONFIG_SYSFS_DEPRECATED) && defined(CONFIG_BLOCK)
	187	+#if defined(CONFIG_BLOCK)
188	188	/* let the block class directory show up in the root of sysfs */
189		- if (cls != &block_class)
	189	+ if (!sysfs_deprecated \|\| cls != &block_class)
190	190	cp->class_subsys.kobj.kset = class_kset;
191	191	#else
192	192	cp->class_subsys.kobj.kset = class_kset;
...	...	@@ -26,6 +26,19 @@
26	26	#include "base.h"
27	27	#include "power/power.h"
28	28
	29	+#ifdef CONFIG_SYSFS_DEPRECATED
	30	+#ifdef CONFIG_SYSFS_DEPRECATED_V2
	31	+long sysfs_deprecated = 1;
	32	+#else
	33	+long sysfs_deprecated = 0;
	34	+#endif
	35	+static __init int sysfs_deprecated_setup(char *arg)
	36	+{
	37	+ return strict_strtol(arg, 10, &sysfs_deprecated);
	38	+}
	39	+early_param("sysfs.deprecated", sysfs_deprecated_setup);
	40	+#endif
	41	+
29	42	int (platform_notify)(struct device dev) = NULL;
30	43	int (platform_notify_remove)(struct device dev) = NULL;
31	44	static struct kobject *dev_kobj;
32	45
33	46
...	...	@@ -617,14 +630,13 @@
617	630	struct kobject *parent_kobj;
618	631	struct kobject *k;
619	632
620		-#ifdef CONFIG_SYSFS_DEPRECATED
621	633	/* block disks show up in /sys/block */
622		- if (dev->class == &block_class) {
	634	+ if (sysfs_deprecated && dev->class == &block_class) {
623	635	if (parent && parent->class == &block_class)
624	636	return &parent->kobj;
625	637	return &block_class.p->class_subsys.kobj;
626	638	}
627		-#endif
	639	+
628	640	/*
629	641	* If we have no parent, we live in "virtual".
630	642	* Class-devices with a non class-device as parent, live
631	643
632	644
...	...	@@ -707,11 +719,9 @@
707	719	goto out_subsys;
708	720	}
709	721
710		-#ifdef CONFIG_SYSFS_DEPRECATED
711	722	/* /sys/block has directories and does not need symlinks */
712		- if (dev->class == &block_class)
	723	+ if (sysfs_deprecated && dev->class == &block_class)
713	724	return 0;
714		-#endif
715	725
716	726	/* link in the class directory pointing to the device */
717	727	error = sysfs_create_link(&dev->class->p->class_subsys.kobj,
718	728
...	...	@@ -738,10 +748,8 @@
738	748	if (dev->parent && device_is_not_partition(dev))
739	749	sysfs_remove_link(&dev->kobj, "device");
740	750	sysfs_remove_link(&dev->kobj, "subsystem");
741		-#ifdef CONFIG_SYSFS_DEPRECATED
742		- if (dev->class == &block_class)
	751	+ if (sysfs_deprecated && dev->class == &block_class)
743	752	return;
744		-#endif
745	753	sysfs_delete_link(&dev->class->p->class_subsys.kobj, &dev->kobj, dev_name(dev));
746	754	}
747	755
...	...	@@ -513,14 +513,14 @@
513	513
514	514	if (device_add(ddev))
515	515	return;
516		-#ifndef CONFIG_SYSFS_DEPRECATED
517		- err = sysfs_create_link(block_depr, &ddev->kobj,
518		- kobject_name(&ddev->kobj));
519		- if (err) {
520		- device_del(ddev);
521		- return;
	516	+ if (!sysfs_deprecated) {
	517	+ err = sysfs_create_link(block_depr, &ddev->kobj,
	518	+ kobject_name(&ddev->kobj));
	519	+ if (err) {
	520	+ device_del(ddev);
	521	+ return;
	522	+ }
522	523	}
523		-#endif
524	524	disk->part0.holder_dir = kobject_create_and_add("holders", &ddev->kobj);
525	525	disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);
526	526
...	...	@@ -737,9 +737,8 @@
737	737	kobject_put(disk->part0.holder_dir);
738	738	kobject_put(disk->slave_dir);
739	739	disk->driverfs_dev = NULL;
740		-#ifndef CONFIG_SYSFS_DEPRECATED
741		- sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
742		-#endif
	740	+ if (!sysfs_deprecated)
	741	+ sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
743	742	device_del(disk_to_dev(disk));
744	743	}
...	...	@@ -751,5 +751,12 @@
751	751	MODULE_ALIAS("char-major-" __stringify(major) "-" __stringify(minor))
752	752	#define MODULE_ALIAS_CHARDEV_MAJOR(major) \
753	753	MODULE_ALIAS("char-major-" __stringify(major) "-*")
	754	+
	755	+#ifdef CONFIG_SYSFS_DEPRECATED
	756	+extern long sysfs_deprecated;
	757	+#else
	758	+#define sysfs_deprecated 0
	759	+#endif
	760	+
754	761	#endif /* _DEVICE_H_ */
...	...	@@ -660,9 +660,13 @@
660	660	depends on SYSFS
661	661	default n
662	662	help
663		- This option switches the layout of the "block" class devices, to not
664		- show up in /sys/class/block/, but only in /sys/block/.
	663	+ This option adds code that switches the layout of the "block" class
	664	+ devices, to not show up in /sys/class/block/, but only in
	665	+ /sys/block/.
665	666
	667	+ This switch is only active when the sysfs.deprecated=1 boot option is
	668	+ passed or the SYSFS_DEPRECATED_V2 option is set.
	669	+
666	670	This option allows new kernels to run on old distributions and tools,
667	671	which might get confused by /sys/class/block/. Since 2007/2008 all
668	672	major distributions and tools handle this just fine.
...	...	@@ -672,8 +676,22 @@
672	676	option enabled.
673	677
674	678	Only if you are using a new kernel on an old distribution, you might
675		- need to say Y here. Never say Y, if the original kernel, that came
676		- with your distribution, has not set this option.
	679	+ need to say Y here.
	680	+
	681	+config SYSFS_DEPRECATED_V2
	682	+ bool "enabled deprecated sysfs features by default"
	683	+ default n
	684	+ depends on SYSFS
	685	+ depends on SYSFS_DEPRECATED
	686	+ help
	687	+ Enable deprecated sysfs by default.
	688	+
	689	+ See the CONFIG_SYSFS_DEPRECATED option for more details about this
	690	+ option.
	691	+
	692	+ Only if you are using a new kernel on an old distribution, you might
	693	+ need to say Y here. Even then, odds are you would not need it
	694	+ enabled, you can always pass the boot option if absolutely necessary.
677	695
678	696	config RELAY
679	697	bool "Kernel->user space relay support (formerly relayfs)"