Quoting Eric W. Biederman (ebiederm@xmission.com):
> "Serge E. Hallyn" <serue@us.ibm.com> writes:
> 
> >> > Where the latter is needed in, for instance, kernel/capability.c.
> >> 
> >> Yes.
> >> 
> >> I think more clear cut examples could be made.  It isn't clear to me
> >> why we skip pid == 1 in kernel/capability.c
> >
> > Because the capset(2) manpage says:
> >
> > 	For capset(), pid can also be: -1, meaning
> >        perform  the  change on all threads except the caller and
> >        init(8); 
> 
> Which they copied from the kill(2) manpage.  So they are just preserving
> the existing definition of which processes -1 applies to.
> 
> The single unix/posix standard says:
> 
>     If pid is -1, sig shall be sent to all processes (excluding an
>     unspecified set of system processes) for which the process has
>     permission to send that signal.
> 
> So I'm still curious why we decided not to send to pid == 1.  But
> that is clearly the way things are defined to work in linux.
> 
> So I guess that makes the capsetall case a good example after all.
> It is skipping pid == 1 because that is what it means.  And in that
> context I suspect makes a great deal of sense to perform the skip
> by testing for pid == 1.  Because that is what we really mean.

Ok, so please tear this apart as a first shot at splitting up is_init.

Note that near as I can tell, some callers of is_init() have been
changed back to pid==1 checks in Linus' tree.  I'm ignoring those
for now.

-serge

From: "Serge E. Hallyn" <serue@us.ibm.com>
Subject: [PATCH] pid namespaces: define is_global_init()

is_init() is an ambiguous name for the pid==1 check.  Split it into is_global_init()
and is_container_init().  is_container_init() cannot yet be defined because it will
need to use pid namespace feautures which do not yet exist in mainline.  It is
currently the same as is_global_init(), but the comment above describes how it
should be defined.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>

---

 arch/alpha/mm/fault.c                |    2 +-
 arch/arm/mm/fault.c                  |    2 +-
 arch/arm26/mm/fault.c                |    2 +-
 arch/i386/lib/usercopy.c             |    2 +-
 arch/i386/mm/fault.c                 |    2 +-
 arch/ia64/mm/fault.c                 |    2 +-
 arch/m32r/mm/fault.c                 |    2 +-
 arch/m68k/mm/fault.c                 |    2 +-
 arch/mips/mm/fault.c                 |    2 +-
 arch/powerpc/kernel/traps.c          |    2 +-
 arch/powerpc/mm/fault.c              |    2 +-
 arch/powerpc/platforms/pseries/ras.c |    2 +-
 arch/ppc/kernel/traps.c              |    2 +-
 arch/ppc/mm/fault.c                  |    2 +-
 arch/s390/lib/uaccess_pt.c           |    2 +-
 arch/s390/mm/fault.c                 |    2 +-
 arch/sh/mm/fault.c                   |    2 +-
 arch/sh64/mm/fault.c                 |    6 +++---
 arch/um/kernel/trap.c                |    2 +-
 arch/x86_64/mm/fault.c               |    4 ++--
 arch/xtensa/mm/fault.c               |    2 +-
 drivers/char/sysrq.c                 |    2 +-
 include/linux/pid_namespace.h        |    3 +++
 include/linux/sched.h                |    7 +++++--
 kernel/capability.c                  |    3 ++-
 kernel/exit.c                        |    2 +-
 kernel/kexec.c                       |    2 +-
 kernel/sched.c                       |   14 ++++++++++++++
 kernel/sysctl.c                      |    2 +-
 mm/oom_kill.c                        |    4 ++--
 security/commoncap.c                 |    2 +-
 31 files changed, 55 insertions(+), 34 deletions(-)

d0bb7398482666dbfda6e4e6efd5c773dea0d586
diff --git a/arch/alpha/mm/fault.c b/arch/alpha/mm/fault.c
index 8aa9db8..44e10aa 100644
--- a/arch/alpha/mm/fault.c
+++ b/arch/alpha/mm/fault.c
@@ -193,7 +193,7 @@ do_page_fault(unsigned long address, uns
 	/* We ran out of memory, or some other thing happened to us that
 	   made us unable to handle the page fault gracefully.  */
  out_of_memory:
-	if (is_init(current)) {
+	if (is_global_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 9fd6d2e..2b3647a 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -198,7 +198,7 @@ survive:
 		return fault;
 	}
 
-	if (!is_init(tsk))
+	if (!is_global_init(tsk))
 		goto out;
 
 	/*
diff --git a/arch/arm26/mm/fault.c b/arch/arm26/mm/fault.c
index 93c0cee..1b22594 100644
--- a/arch/arm26/mm/fault.c
+++ b/arch/arm26/mm/fault.c
@@ -185,7 +185,7 @@ survive:
 	}
 
 	fault = -3; /* out of memory */
-	if (!is_init(tsk))
+	if (!is_global_init(tsk))
 		goto out;
 
 	/*
diff --git a/arch/i386/lib/usercopy.c b/arch/i386/lib/usercopy.c
index d22cfc9..6f0e3fc 100644
--- a/arch/i386/lib/usercopy.c
+++ b/arch/i386/lib/usercopy.c
@@ -740,7 +740,7 @@ survive:
 			retval = get_user_pages(current, current->mm,
 					(unsigned long )to, 1, 1, 0, &pg, NULL);
 
-			if (retval == -ENOMEM && is_init(current)) {
+			if (retval == -ENOMEM && is_global_init(current)) {
 				up_read(&current->mm->mmap_sem);
 				congestion_wait(WRITE, HZ/50);
 				goto survive;
diff --git a/arch/i386/mm/fault.c b/arch/i386/mm/fault.c
index b8c4e25..1dd8ca8 100644
--- a/arch/i386/mm/fault.c
+++ b/arch/i386/mm/fault.c
@@ -561,7 +561,7 @@ no_context:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (is_init(tsk)) {
+	if (is_global_init(tsk)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index 59f3ab9..c0f73a1 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -280,7 +280,7 @@ ia64_do_page_fault (unsigned long addres
 
   out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (is_init(current)) {
+	if (is_global_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/m32r/mm/fault.c b/arch/m32r/mm/fault.c
index 037d58e..75dce7f 100644
--- a/arch/m32r/mm/fault.c
+++ b/arch/m32r/mm/fault.c
@@ -273,7 +273,7 @@ no_context:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (is_init(tsk)) {
+	if (is_global_init(tsk)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
index 2adbeb1..a9a08b0 100644
--- a/arch/m68k/mm/fault.c
+++ b/arch/m68k/mm/fault.c
@@ -181,7 +181,7 @@ good_area:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (is_init(current)) {
+	if (is_global_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
index 6f90e7e..2b20e4d 100644
--- a/arch/mips/mm/fault.c
+++ b/arch/mips/mm/fault.c
@@ -175,7 +175,7 @@ no_context:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (is_init(tsk)) {
+	if (is_global_init(tsk)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 17724fb..939e723 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -172,7 +172,7 @@ void _exception(int signr, struct pt_reg
 	 * generate the same exception over and over again and we get
 	 * nowhere.  Better to kill it and let the kernel panic.
 	 */
-	if (is_init(current)) {
+	if (is_container_init(current, NULL)) {
 		__sighandler_t handler;
 
 		spin_lock_irq(&current->sighand->siglock);
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 03aeb3a..691f212 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -386,7 +386,7 @@ bad_area_nosemaphore:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (is_init(current)) {
+	if (is_global_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index edc0388..3f6bd53 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -333,7 +333,7 @@ static int recover_mce(struct pt_regs *r
 		   err->disposition == RTAS_DISP_NOT_RECOVERED &&
 		   err->target == RTAS_TARGET_MEMORY &&
 		   err->type == RTAS_TYPE_ECC_UNCORR &&
-		   !(current->pid == 0 || is_init(current))) {
+		   !(current->pid == 0 || is_global_init(current))) {
 		/* Kill off a user process with an ECC error */
 		printk(KERN_ERR "MCE: uncorrectable ecc error for pid %d\n",
 		       current->pid);
diff --git a/arch/ppc/kernel/traps.c b/arch/ppc/kernel/traps.c
index 810f7aa..80a5fa4 100644
--- a/arch/ppc/kernel/traps.c
+++ b/arch/ppc/kernel/traps.c
@@ -120,7 +120,7 @@ void _exception(int signr, struct pt_reg
 	 * generate the same exception over and over again and we get
 	 * nowhere.  Better to kill it and let the kernel panic.
 	 */
-	if (is_init(current)) {
+	if (is_container_init(current, NULL)) {
 		__sighandler_t handler;
 
 		spin_lock_irq(&current->sighand->siglock);
diff --git a/arch/ppc/mm/fault.c b/arch/ppc/mm/fault.c
index 465f451..a370002 100644
--- a/arch/ppc/mm/fault.c
+++ b/arch/ppc/mm/fault.c
@@ -291,7 +291,7 @@ bad_area:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (is_init(current)) {
+	if (is_global_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/s390/lib/uaccess_pt.c b/arch/s390/lib/uaccess_pt.c
index 6318167..6d7e99d 100644
--- a/arch/s390/lib/uaccess_pt.c
+++ b/arch/s390/lib/uaccess_pt.c
@@ -65,7 +65,7 @@ out:
 
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (is_init(current)) {
+	if (is_global_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 7462aeb..29eaa0a 100644
--- a/arch/s390/mm/fault.c
+++ b