[PATCH] Remove policy contextualization from mbind

Policy contextualization is only useful for task based policies and not for
vma based policies.  It may be useful to define allowed nodes that are not
accessible from this thread because other threads may have access to these
nodes.  Without this patch strange memory policy situations may cause an
application to fail with out of memory.

Example:

Let's say we have two threads A and B that share the same address space and
a huge array computational array X.

Thread A is restricted by its cpuset to nodes 0 and 1 and thread B is
restricted by its cpuset to nodes 2 and 3.

Thread A now wants to restrict allocations to the first node and thus
applies a BIND policy on X to node 0 and 2.  The cpuset limits this to node
0.  Thus pages for X must be allocated on node 0 now.

Thread B now touches a page that has never been used in X and faults in a
page.  According to the BIND policy of the vma for X the page must be
allocated on page 0.  However, the cpuset of B does not allow allocation on
0 and 1.  Now the application fails in alloc_pages with out of memory.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 123925f50f865a9da0aea8502cb2e9adb491041f..2076b1542b8ac9ce32beba96e051bd70a62ebf96 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -370,7 +370,7 @@ long do_mbind(unsigned long start, unsigned long len,
                return -EINVAL;
        if (end == start)
                return 0;
-       if (contextualize_policy(mode, nmask))
+       if (mpol_check_policy(mode, nmask))
                return -EINVAL;
        new = mpol_new(mode, nmask);
        if (IS_ERR(new))