sysctl: implement CTL_UNNUMBERED

plain text document attachment (sysctl-unnumbered.patch)
From: Eric W. Biederman <[email protected]>

This patch takes the CTL_UNNUMBERD concept from NFS and makes it available to all new sysctl users.

At the same time the sysctl binary interface maintenance documentation is updated to mention and to describe what is needed to successfully maintain the sysctl binary interface.

Signed-off-by Eric W. Biederman <[email protected]>

Acked-by Alan Cox <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Signed-off-by Linus Torvalds <[email protected]>

---
Wed, 19 Sep 2007 15:17:27 +0900:
This is a backport of some code for Linux that is needed by my backport of kexec to IA64 xen. As it patches common code Alex Williams asked me to submitt it to xen-devel, so here it is.

Linux upstream, commit 7cc13edc139108bb527b692f0548dce6bc648572

 fs/lockd/svc.c         |    3 ---
 fs/nfs/sysctl.c        |    5 -----
 include/linux/sysctl.h |   14 +++++++++++---
 3 files changed, 11 insertions(+), 11 deletions(-)

fs/lockd/svc.c +0 -3

index 6341392..8ca1808 100644
@@ -353,9 +353,6 @@ EXPORT_SYMBOL(lockd_down);
  * Sysctl parameters (same as module parameters, different interface).
  */
 
-/* Something that isn't CTL_ANY, CTL_NONE or a value that may clash. */
-#define CTL_UNNUMBERED		-2
-
 static ctl_table nlm_sysctls[] = {
 	{
 		.ctl_name	= CTL_UNNUMBERED,

fs/nfs/sysctl.c +0 -5

index 2fe3403..3ea50ac 100644
@@ -18,11 +18,6 @@
 static const int nfs_set_port_min = 0;
 static const int nfs_set_port_max = 65535;
 static struct ctl_table_header *nfs_callback_sysctl_table;
-/*
- * Something that isn't CTL_ANY, CTL_NONE or a value that may clash.
- * Use the same values as fs/lockd/svc.c
- */
-#define CTL_UNNUMBERED -2
 
 static ctl_table nfs_cb_sysctls[] = {
 #ifdef CONFIG_NFS_V4

include/linux/sysctl.h +11 -3

index c184732..d98562f 100644
@@ -6,10 +6,17 @@
  ****************************************************************
  ****************************************************************
  **
+ **  WARNING:
  **  The values in this file are exported to user space via 
- **  the sysctl() binary interface.  However this interface
- **  is unstable and deprecated and will be removed in the future. 
- **  For a stable interface use /proc/sys.
+ **  the sysctl() binary interface.  Do *NOT* change the
+ **  numbering of any existing values here, and do not change
+ **  any numbers within any one set of values.  If you have to
+ **  have to redefine an existing interface, use a new number for it.
+ **  The kernel will then return -ENOTDIR to any application using
+ **  the old binary interface.
+ **
+ **  For new interfaces unless you really need a binary number
+ **  please use CTL_UNNUMBERED.
  **
  ****************************************************************
  ****************************************************************

@@ -48,6 +55,7 @@ struct __sysctl_args {
 #ifdef __KERNEL__
 #define CTL_ANY		-1	/* Matches any name */
 #define CTL_NONE	0
+#define CTL_UNNUMBERED	CTL_NONE	/* sysctl without a binary number */
 #endif
 
 enum

Signature · 1 line

-- 

Keir already took this:
http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/aaf32d3bdc8b

It's just this morning got unblocked from the staging tree though.