linux-stable.git/kernel/cpuset.c, branch linux-2.6.19.y

[PATCH] cpuset ANSI prototype

2006-10-10T22:37:23+00:00

Signed-off-by: Al Viro 
Acked-by: Paul Jackson 
Signed-off-by: Linus Torvalds

[PATCH] r/o bind mount prepwork: inc_nlink() helper

2006-10-01T07:39:30+00:00

This is mostly included for parity with dec_nlink(), where we will have some
more hooks.  This one should stay pretty darn straightforward for now.

Signed-off-by: Dave Hansen 
Acked-by: Christoph Hellwig 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] cpuset: fix obscure attach_task vs exiting race

2006-09-29T16:18:25+00:00

Fix obscure race condition in kernel/cpuset.c attach_task() code.

There is basically zero chance of anyone accidentally being harmed by this
race.

It requires a special 'micro-stress' load and a special timing loop hacks
in the kernel to hit in less than an hour, and even then you'd have to hit
it hundreds or thousands of times, followed by some unusual and senseless
cpuset configuration requests, including removing the top cpuset, to cause
any visibly harm affects.

One could, with perhaps a few days or weeks of such effort, get the
reference count on the top cpuset below zero, and manage to crash the
kernel by asking to remove the top cpuset.

I found it by code inspection.

The race was introduced when 'the_top_cpuset_hack' was introduced, and one
piece of code was not updated.  An old check for a possibly null task
cpuset pointer needed to be changed to a check for a task marked
PF_EXITING.  The pointer can't be null anymore, thanks to
the_top_cpuset_hack (documented in kernel/cpuset.c).  But the task could
have gone into PF_EXITING state after it was found in the task_list scan.

If a task is PF_EXITING in this code, it is possible that its task->cpuset
pointer is pointing to the top cpuset due to the_top_cpuset_hack, rather
than because the top_cpuset was that tasks last valid cpuset.  In that
case, the wrong cpuset reference counter would be decremented.

The fix is trivial.  Instead of failing the system call if the tasks cpuset
pointer is null here, fail it if the task is in PF_EXITING state.

The code for 'the_top_cpuset_hack' that changes an exiting tasks cpuset to
the top_cpuset is done without locking, so could happen at anytime.  But it
is done during the exit handling, after the PF_EXITING flag is set.  So if
we verify that a task is still not PF_EXITING after we copy out its cpuset
pointer (into 'oldcs', below), we know that 'oldcs' is not one of these
hack references to the top_cpuset.

Signed-off-by: Paul Jackson 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] cpuset: hotunplug cpus and mems in all cpusets

2006-09-29T16:18:21+00:00

The cpuset code handling hot unplug of CPUs or Memory Nodes was incorrect -
it could remove a CPU or Node from the top cpuset, while leaving it still
in some child cpusets.

One basic rule of cpusets is that each cpusets cpus and mems are subsets of
its parents.  The cpuset hot unplug code violated this rule.

So the cpuset hotunplug handler must walk down the tree, removing any
removed CPU or Node from all cpusets.

However, it is not allowed to make a cpusets cpus or mems become empty.
They can only transition from empty to non-empty, not back.

So if the last CPU or Node would be removed from a cpuset by the above
walk, we scan back up the cpuset hierarchy, finding the nearest ancestor
that still has something online, and copy its CPU or Memory placement.

Signed-off-by: Paul Jackson 
Cc: Nathan Lynch 
Cc: Anton Blanchard 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] cpuset: top_cpuset tracks hotplug changes to node_online_map

2006-09-29T16:18:21+00:00

Change the list of memory nodes allowed to tasks in the top (root) nodeset
to dynamically track what cpus are online, using a call to a cpuset hook
from the memory hotplug code.  Make this top cpus file read-only.

On systems that have cpusets configured in their kernel, but that aren't
actively using cpusets (for some distros, this covers the majority of
systems) all tasks end up in the top cpuset.

If that system does support memory hotplug, then these tasks cannot make
use of memory nodes that are added after system boot, because the memory
nodes are not allowed in the top cpuset.  This is a surprising regression
over earlier kernels that didn't have cpusets enabled.

One key motivation for this change is to remain consistent with the
behaviour for the top_cpuset's 'cpus', which is also read-only, and which
automatically tracks the cpu_online_map.

This change also has the minor benefit that it fixes a long standing,
little noticed, minor bug in cpusets.  The cpuset performance tweak to
short circuit the cpuset_zone_allowed() check on systems with just a single
cpuset (see 'number_of_cpusets', in linux/cpuset.h) meant that simply
changing the 'mems' of the top_cpuset had no affect, even though the change
(the write system call) appeared to succeed.  With the following change,
that write to the 'mems' file fails -EACCES, and the 'mems' file stubbornly
refuses to be changed via user space writes.  Thus no one should be mislead
into thinking they've changed the top_cpusets's 'mems' when in affect they
haven't.

In order to keep the behaviour of cpusets consistent between systems
actively making use of them and systems not using them, this patch changes
the behaviour of the 'mems' file in the top (root) cpuset, making it read
only, and making it automatically track the value of node_online_map.  Thus
tasks in the top cpuset will have automatic use of hot plugged memory nodes
allowed by their cpuset.

[akpm@osdl.org: build fix]
[bunk@stusta.de: build fix]
Signed-off-by: Paul Jackson 
Signed-off-by: Adrian Bunk 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] pidspace: is_init()

2006-09-29T16:18:12+00:00

This is an updated version of Eric Biederman's is_init() patch.
(http://lkml.org/lkml/2006/2/6/280).  It applies cleanly to 2.6.18-rc3 and
replaces a few more instances of ->pid == 1 with is_init().

Further, is_init() checks pid and thus removes dependency on Eric's other
patches for now.

Eric's original description:

	There are a lot of places in the kernel where we test for init
	because we give it special properties.  Most  significantly init
	must not die.  This results in code all over the kernel test
	->pid == 1.

	Introduce is_init to capture this case.

	With multiple pid spaces for all of the cases affected we are
	looking for only the first process on the system, not some other
	process that has pid == 1.

Signed-off-by: Eric W. Biederman 
Signed-off-by: Sukadev Bhattiprolu 
Cc: Dave Hansen 
Cc: Serge Hallyn 
Cc: Cedric Le Goater 
Cc: 
Acked-by: Paul Mackerras 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] inode-diet: Eliminate i_blksize from the inode structure

2006-09-27T15:26:18+00:00

This eliminates the i_blksize field from struct inode.  Filesystems that want
to provide a per-inode st_blksize can do so by providing their own getattr
routine instead of using the generic_fillattr() function.

Note that some filesystems were providing pretty much random (and incorrect)
values for i_blksize.

[bunk@stusta.de: cleanup]
[akpm@osdl.org: generic_fillattr() fix]
Signed-off-by: "Theodore Ts'o" 
Signed-off-by: Adrian Bunk 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] NUMA: Add zone_to_nid function

2006-09-26T15:48:52+00:00

There are many places where we need to determine the node of a zone.
Currently we use a difficult to read sequence of pointer dereferencing.
Put that into an inline function and use throughout VM.  Maybe we can find
a way to optimize the lookup in the future.

Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Add __GFP_THISNODE to avoid fallback to other nodes and ignore cpuset/memory policy restrictions

2006-09-26T15:48:50+00:00

Add a new gfp flag __GFP_THISNODE to avoid fallback to other nodes.  This
flag is essential if a kernel component requires memory to be located on a
certain node.  It will be needed for alloc_pages_node() to force allocation
on the indicated node and for alloc_pages() to force allocation on the
current node.

Signed-off-by: Christoph Lameter 
Cc: Andy Whitcroft 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] cpuset: oom panic fix

2006-08-27T18:01:32+00:00

cpuset_excl_nodes_overlap always returns 0 if current is exiting.  This caused
customer's systems to panic in the OOM killer when processes were having
trouble getting memory for the final put_user in mm_release.  Even though
there were lots of processes to kill.

Change to returning 1 in this case.  This achieves parity with !CONFIG_CPUSETS
case, and was observed to fix the problem.

Signed-off-by: Nick Piggin 
Acked-by: Paul Jackson 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds