[Patch] Selective removal mode for udev

[Patch] Selective removal mode for udev

[Hannes Reinecke]

[-- Attachment #1: Type: text/plain, Size: 742 bytes --]

Because we are chicken ...

This patch adds a 'removal' mode for udev, with three possible choices:

- all: default behaviour; remove all nodes and symlinks
- symlink_only: only remove symlinks, but keep device nodes
- none: do not remove nodes nor symlinks.

The latter is equivalent with the existing 'ignore_remove' rule 
statement, but implemented as a global switch.

Properly documented in the man-page etc.

This is basically for those worrying about 'my device node may be 
vanishing and ooh everything will stop working'.

Comments etc welcome.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke			hare@suse.de
SuSE Linux AG				S390 & zSeries
Maxfeldstraße 5				+49 911 74053 688
90409 Nürnberg				http://www.suse.de

[-- Attachment #2: udev-052-keep-devicenodes.patch --]
[-- Type: text/x-patch, Size: 3364 bytes --]

===== udev.8.in 1.77 vs edited =====
--- 1.77/udev.8.in	2005-02-10 01:03:54 +01:00
+++ edited/udev.8.in	2005-02-11 09:41:11 +01:00
@@ -59,6 +59,21 @@
 The switch to enable/disable logging of udev information
 The default value is
 .IR yes .
+.TP
+.B udev_remove
+Configure the behaviour for remove events. Possible values are
+.IR all ,
+.IR symlinks_only ,
+.IR none .
+When set to
+.IR all ,
+udev will remove all device information (this is the default). When
+set to
+.IR symlinks_only ,
+udev will remove all symlinks but leave the device node
+intact. When set to
+.IR none ,
+udev will not remove any device information.
 .P
 .RI "A sample " udev.conf " file might look like this:
 .sp
===== udev_config.c 1.31 vs edited =====
--- 1.31/udev_config.c	2005-01-04 21:37:01 +01:00
+++ edited/udev_config.c	2005-02-11 10:04:16 +01:00
@@ -48,6 +48,7 @@
 int udev_log;
 int udev_dev_d;
 int udev_hotplug_d;
+int udev_remove_mode = UDEV_REMOVE_ALL;
 
 
 static int string_is_true(const char *str)
@@ -164,6 +165,17 @@
 
 		if (strcasecmp(variable, "udev_log") == 0) {
 			udev_log = string_is_true(value);
+			continue;
+		}
+
+		if (strcasecmp(variable, "udev_remove") == 0) {
+			if (strcasecmp(value,"all") == 0) {
+				udev_remove_mode=UDEV_REMOVE_ALL;
+			} else if (strcasecmp(value,"symlinks_only") == 0) {
+				udev_remove_mode=UDEV_REMOVE_SYMLINKS;
+			} else if (strcasecmp(value,"none")) {
+				udev_remove_mode=UDEV_REMOVE_NONE;
+			}
 			continue;
 		}
 	}
===== udev_db.c 1.41 vs edited =====
--- 1.41/udev_db.c	2005-02-04 18:38:55 +01:00
+++ edited/udev_db.c	2005-02-11 09:45:54 +01:00
@@ -165,6 +165,11 @@
 	get_db_filename(udev, filename, SYSFS_PATH_MAX);
 	unlink(filename);
 
+	if (udev_remove_mode == UDEV_REMOVE_SYMLINKS) {
+		memset(udev->symlink, 0, NAME_SIZE);
+		udev_db_add_device(udev);
+	}
+
 	return 0;
 }
 
===== udev.h 1.84 vs edited =====
--- 1.84/udev.h	2005-02-09 00:43:18 +01:00
+++ edited/udev.h	2005-02-11 09:32:14 +01:00
@@ -48,6 +48,11 @@
 
 #define DEFAULT_PARTITIONS_COUNT	15
 
+/* Removal modes to keep whiners happy */
+#define UDEV_REMOVE_ALL			0
+#define UDEV_REMOVE_SYMLINKS		1
+#define UDEV_REMOVE_NONE		2
+
 struct udevice {
 	char devpath[DEVPATH_SIZE];
 	char subsystem[SUBSYSTEM_SIZE];
@@ -89,5 +94,6 @@
 extern int udev_log;
 extern int udev_dev_d;
 extern int udev_hotplug_d;
+extern int udev_remove_mode;
 
 #endif
===== udev_remove.c 1.45 vs edited =====
--- 1.45/udev_remove.c	2005-02-09 00:43:18 +01:00
+++ edited/udev_remove.c	2005-02-11 10:07:52 +01:00
@@ -80,6 +80,11 @@
 	snprintf(filename, NAME_SIZE, "%s/%s", udev_root, udev->name);
 	filename[NAME_SIZE-1] = '\0';
 
+	if (udev_remove_mode == UDEV_REMOVE_SYMLINKS) {
+		dbg("remove device nodes for '%s' requested to be ignored by config", udev->name);
+		goto remove_symlinks;
+	}
+
 	info("removing device node '%s'", filename);
 	retval = unlink_secure(filename);
 	if (retval)
@@ -104,6 +109,7 @@
 	if (strchr(udev->name, '/'))
 		delete_path(filename);
 
+ remove_symlinks:
 	foreach_strpart(udev->symlink, " ", pos, len) {
 		char linkname[NAME_SIZE];
 
@@ -152,6 +158,11 @@
 
 	if (udev->ignore_remove) {
 		dbg("remove event for '%s' requested to be ignored by rule", udev->name);
+		return 0;
+	}
+
+	if (udev_remove_mode == UDEV_REMOVE_NONE) {
+		dbg("remove event for '%s' requested to be ignored by config", udev->name);
 		return 0;
 	}
 

Re: [Patch] Selective removal mode for udev

[Kay Sievers]

On Fri, 2005-02-11 at 10:18 +0100, Hannes Reinecke wrote:
>Because we are chicken ...
>
>This patch adds a 'removal' mode for udev, with three possible choices:
>
>- all: default behaviour; remove all nodes and symlinks
>- symlink_only: only remove symlinks, but keep device nodes
>- none: do not remove nodes nor symlinks.
>
>The latter is equivalent with the existing 'ignore_remove' rule 
>statement, but implemented as a global switch.
>
>Properly documented in the man-page etc.
>
>This is basically for those worrying about 'my device node may be 
>vanishing and ooh everything will stop working'.
>
>Comments etc welcome.

Hmm, wouldn't it be nicer to be able to set these things along with the
rules, so we still have only one source of policy. And we are able to
match against SUBSYSTEMS, DRIVERS and such things?

Something like an OPTIONS="..." key, which may contain a list of keys
and we can also move the no_partitions key into that.

This way we can specify the "remove-policy" with an "option" only rule
globally or only for a certain subsystem.

How does that sound?

Kay



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Re: [Patch] Selective removal mode for udev

[Christian Zoz]

On Fri, Feb 11, Kay Sievers wrote:
> On Fri, 2005-02-11 at 10:18 +0100, Hannes Reinecke wrote:
> >Because we are chicken ...
> >
> >This patch adds a 'removal' mode for udev, with three possible choices:
> >
> >- all: default behaviour; remove all nodes and symlinks
> >- symlink_only: only remove symlinks, but keep device nodes
> >- none: do not remove nodes nor symlinks.
> >
> >The latter is equivalent with the existing 'ignore_remove' rule 
> >statement, but implemented as a global switch.
> 
> Hmm, wouldn't it be nicer to be able to set these things along with the
> rules, so we still have only one source of policy. And we are able to
> match against SUBSYSTEMS, DRIVERS and such things?
> 
> Something like an OPTIONS="..." key, which may contain a list of keys
> and we can also move the no_partitions key into that.
> 
> This way we can specify the "remove-policy" with an "option" only rule
> globally or only for a certain subsystem.

For indiviual rules there is ignore_remove. And as a global switch an
option in udev.conf is much easier. The user needs no knowldege about
rule writing.

-- 

ciao, christian

睡眠不足はいい仕事の敵だ。


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Re: [Patch] Selective removal mode for udev

[Kay Sievers]

On Fri, 2005-02-11 at 11:15 +0100, Christian Zoz wrote:
>On Fri, Feb 11, Kay Sievers wrote:
>> On Fri, 2005-02-11 at 10:18 +0100, Hannes Reinecke wrote:
>> >Because we are chicken ...
>> >
>> >This patch adds a 'removal' mode for udev, with three possible choices:
>> >
>> >- all: default behaviour; remove all nodes and symlinks
>> >- symlink_only: only remove symlinks, but keep device nodes
>> >- none: do not remove nodes nor symlinks.
>> >
>> >The latter is equivalent with the existing 'ignore_remove' rule 
>> >statement, but implemented as a global switch.
>> 
>> Hmm, wouldn't it be nicer to be able to set these things along with the
>> rules, so we still have only one source of policy. And we are able to
>> match against SUBSYSTEMS, DRIVERS and such things?
>> 
>> Something like an OPTIONS="..." key, which may contain a list of keys
>> and we can also move the no_partitions key into that.
>> 
>> This way we can specify the "remove-policy" with an "option" only rule
>> globally or only for a certain subsystem.
>
>For indiviual rules there is ignore_remove. And as a global switch an
>option in udev.conf is much easier. The user needs no knowldege about
>rule writing.

You shouldn't change udev.conf, if you don't know how to write rules. :)

The point is that it's nice to have _all_ policy from one source.
One line with:
  OPTIONS="no_remove"

will do the same as the config option. But you can limit its focus with
additional keys to certain devices if needed.
We've removed the default permissions settings from udev.conf for the
same reason.

Thanks,
Kay



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Re: [Patch] Selective removal mode for udev

[Hannes Reinecke]

Kay Sievers wrote:
> On Fri, 2005-02-11 at 11:15 +0100, Christian Zoz wrote:
>>On Fri, Feb 11, Kay Sievers wrote:
[ .. ]
>>>Hmm, wouldn't it be nicer to be able to set these things along with the
>>>rules, so we still have only one source of policy. And we are able to
>>>match against SUBSYSTEMS, DRIVERS and such things?
>>>
>>>Something like an OPTIONS="..." key, which may contain a list of keys
>>>and we can also move the no_partitions key into that.
>>>
>>>This way we can specify the "remove-policy" with an "option" only rule
>>>globally or only for a certain subsystem.
>>For indiviual rules there is ignore_remove. And as a global switch an
>>option in udev.conf is much easier. The user needs no knowldege about
>>rule writing.
> 
> You shouldn't change udev.conf, if you don't know how to write rules. :)
> 
> The point is that it's nice to have _all_ policy from one source.
> One line with:
>   OPTIONS="no_remove"
> 
> will do the same as the config option. But you can limit its focus with
> additional keys to certain devices if needed.
> We've removed the default permissions settings from udev.conf for the
> same reason.
> 
Yes, this sounds reasonable.

Proposed format:

OPTIONS=<optargs>
<optargs> := "<arg>(,<arg>)*"
<arg> := ignore_scripts|remove_none|remove_symlinks

No, since we're having several options I consider it quite a waste to 
store every option with one line in the database. Can't we just use a 
bitmap for it? Would simplify handling quite a lot ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke			hare@suse.de
SuSE Linux AG				S390 & zSeries
Maxfeldstraße 5				+49 911 74053 688
90409 Nürnberg				http://www.suse.de


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Re: [Patch] Selective removal mode for udev

[Kay Sievers]

On Fri, Feb 11, 2005 at 10:52:28AM +0100, Kay Sievers wrote:
> On Fri, 2005-02-11 at 10:18 +0100, Hannes Reinecke wrote:
> >Because we are chicken ...
> >
> >This patch adds a 'removal' mode for udev, with three possible choices:
> >
> >- all: default behaviour; remove all nodes and symlinks
> >- symlink_only: only remove symlinks, but keep device nodes
> >- none: do not remove nodes nor symlinks.
> >
> >The latter is equivalent with the existing 'ignore_remove' rule 
> >statement, but implemented as a global switch.
> >
> >Properly documented in the man-page etc.
> >
> >This is basically for those worrying about 'my device node may be 
> >vanishing and ooh everything will stop working'.
> >
> >Comments etc welcome.
> 
> Hmm, wouldn't it be nicer to be able to set these things along with the
> rules, so we still have only one source of policy. And we are able to
> match against SUBSYSTEMS, DRIVERS and such things?
> 
> Something like an OPTIONS="..." key, which may contain a list of keys
> and we can also move the no_partitions key into that.
> 
> This way we can specify the "remove-policy" with an "option" only rule
> globally or only for a certain subsystem.

I've added something to my tree:
  http://vrfy.bkbits.net:8080/udev/patch@1.1143?nav=cset@1.1143

We have options-only rules now:
  BUS="scsi", SUBSYSTEM="block", SYSFS{removable}="1", OPTIONS="all_partitions"

will create all partitions for all block devices which are known to have removable
media.

It does not implement your remove-only-the-symlinks option. For what was it meant
to be used?

Thanks,
Kay


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Re: [Patch] Selective removal mode for udev

[Hannes Reinecke]

Kay Sievers wrote:
> On Fri, Feb 11, 2005 at 10:52:28AM +0100, Kay Sievers wrote:
> 
>>On Fri, 2005-02-11 at 10:18 +0100, Hannes Reinecke wrote:
>>
>>>Because we are chicken ...
>>>
>>>This patch adds a 'removal' mode for udev, with three possible choices:
>>>
>>>- all: default behaviour; remove all nodes and symlinks
>>>- symlink_only: only remove symlinks, but keep device nodes
>>>- none: do not remove nodes nor symlinks.
>>>
>>>The latter is equivalent with the existing 'ignore_remove' rule 
>>>statement, but implemented as a global switch.
>>>
>>>Properly documented in the man-page etc.
>>>
>>>This is basically for those worrying about 'my device node may be 
>>>vanishing and ooh everything will stop working'.
>>>
>>>Comments etc welcome.
>>
>>Hmm, wouldn't it be nicer to be able to set these things along with the
>>rules, so we still have only one source of policy. And we are able to
>>match against SUBSYSTEMS, DRIVERS and such things?
>>
>>Something like an OPTIONS="..." key, which may contain a list of keys
>>and we can also move the no_partitions key into that.
>>
>>This way we can specify the "remove-policy" with an "option" only rule
>>globally or only for a certain subsystem.
> 
> 
> I've added something to my tree:
>   http://vrfy.bkbits.net:8080/udev/patch@1.1143?nav=cset@1.1143
> 
> We have options-only rules now:
>   BUS="scsi", SUBSYSTEM="block", SYSFS{removable}="1", OPTIONS="all_partitions"
> 
> will create all partitions for all block devices which are known to have removable
> media.
> 
> It does not implement your remove-only-the-symlinks option. For what was it meant
> to be used?
> 
For chickens.

There are some which consider removing of device nodes a bad idea.

This is basically meant to keep them happy whilst others have the choice 
of doing the right thing.
This sort of thing tended to occur during re-partitioning, as the remove 
events in general were far quicker processed than the 'add' events.
Should be resolved with using udev, but arguing with them tends to be 
pointless. Hence this options.

Cheers,

Hannes


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