[PATCH] sysctl: Undeprecate sys_sysctl

[Eric W. Biederman]

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@xxxxxxxxxxxx>
---
 Documentation/feature-removal-schedule.txt |   12 ------------
 init/Kconfig                               |    2 +-
 2 files changed, 1 insertions(+), 13 deletions(-)

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 1ac3c74..d52c4aa 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -53,18 +53,6 @@ Who:	Mauro Carvalho Chehab <mchehab@brtu
 
 ---------------------------
 
-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@xxxxxxxxxxxx>
-
----------------------------
-
 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 c8b2624..e85e554 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -304,7 +304,7 @@ 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
-- 
1.4.2.rc3.g7e18e-dirty

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