[PATCH] sysctl: Undeprecate sys_sysctl

The basic issue is that despite have been deprecated and warned about as a
very bad thing in the man pages since its inception there are a few real
users of sys_sysctl.  It was my assumption that because sysctl had been
deprecated for all of 2.6 there would be no user space users by this point,
so I initially gave sys_sysctl a very short deprecation period.

Now that I know there are a few real users the only sane way to proceed
with deprecation is to push the time limit out to a year or two work and
work with distributions that have big testing pools like fedora core to
find these last remaining users.

Which means that the sys_sysctl interface needs to be maintained in the
meantime.

Since I have provided a technical measure that allows us to add new sysctl
entries without reserving more binary numbers I believe that is enough to
fix the sys_sysctl binary interface maintenance problems, because there is
no longer a need to change the binary interface at all.

Since the sys_sysctl implementation needs to stay around for a while and
the worst of the maintenance issues that caused us to occasionally break
the ABI have been addressed I don't see any advantage in continuing with
the removal of sys_sysctl.

So instead of merely increasing the deprecation period this patch removes
the deprecation of sys_sysctl and modifies the kernel to compile the code
in by default.

With committing to maintain sys_sysctl we get all of the advantages of a
fast interface for anything that needs it.  Currently sys_sysctl is about
5x faster than /proc/sys, for the same string data.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 9 insertions, 22 deletions

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 1ac3c74646e3..d52c4aaaf17f 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -53,18 +53,6 @@ Who:	Mauro Carvalho Chehab <mchehab@brturbo.com.br>
 
 ---------------------------
 
-What:   sys_sysctl
-When:   January 2007
-Why:    The same information is available through /proc/sys and that is the
-        interface user space prefers to use. And there do not appear to be
-        any existing user in user space of sys_sysctl.  The additional
-        maintenance overhead of keeping a set of binary names gets
-        in the way of doing a good job of maintaining this interface.
-
-Who:    Eric Biederman <ebiederm@xmission.com>
-
----------------------------
-
 What:   PCMCIA control ioctl (needed for pcmcia-cs [cardmgr, cardctl])
 When:   November 2005
 Files:  drivers/pcmcia/: pcmcia_ioctl.c
diff --git a/init/Kconfig b/init/Kconfig
index c8b2624af176..176f7e5136c7 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -304,20 +304,19 @@ config UID16
 
 config SYSCTL_SYSCALL
         bool "Sysctl syscall support" if EMBEDDED
-        default n
+        default y
         select SYSCTL
         ---help---
-          Enable the deprecated sysctl system call.  sys_sysctl uses
-          binary paths that have been found to be a major pain to maintain
-          and use.  The interface in /proc/sys is now the primary and what
-          everyone uses.
+          sys_sysctl uses binary paths that have been found challenging
+          to properly maintain and use.  The interface in /proc/sys
+          using paths with ascii names is now the primary path to this
+          information.
 
-          Nothing has been using the binary sysctl interface for some
-          time now so nothing should break if you disable sysctl syscall
-          support, and your kernel will get marginally smaller.
+          Almost nothing using the binary sysctl interface so if you are
+          trying to save some space it is probably safe to disable this,
+          making your kernel marginally smaller.
 
-          Unless you have an application that uses the sys_sysctl interface
-          you should probably say N here.
+          If unsure say Y here.
 
 config KALLSYMS
          bool "Load all symbols for debugging/kksymoops" if EMBEDDED