On Fri, 13 Jul 2007 10:45:07 +0800 Joe Jin <[email protected]> wrote:
> This patch add nid sanity check on alloc_pages_node().
> While two process change nr_hugepages at a system, alloc_fresh_huge_page()
> been called, at this function, nid defined as a static variable, but, there
> is not any protection of, if 2 process called at the same time, maybe pass a
> invalid nid to alloc_pages_node.
>
> We have hit it by following scripts:
>
> #!/bin/bash
> while : ; do
> echo 1000000000000 > /proc/sys/vm/nr_hugepages
> echo 1 > /proc/sys/vm/nr_hugepages
> echo 10000000000000000000 > /proc/sys/vm/nr_hugepages
> echo 0 > /proc/sys/vm/nr_hugepages
> done
>
>
> Run the script at _two_ difference terminal, after a short time, a kernel panic
> info will print.
>
>
> Signed-off-by: Joe Jin <[email protected]>
> ---
>
> --- linux-2.6.22/include/linux/gfp.h.orig 2007-07-12 15:06:23.000000000 +0800
> +++ linux-2.6.22/include/linux/gfp.h 2007-07-12 15:02:59.000000000 +0800
> @@ -133,6 +133,9 @@
> /* Unknown node is current node */
> if (nid < 0)
> nid = numa_node_id();
> +
> + if (unlikely(nid == MAX_NUMNODES))
> + nid = first_node(node_online_map);
>
> return __alloc_pages(gfp_mask, order,
> NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_mask));
alloc_pages_node() is pretty much the last place where we want to fix this:
it adds more cycles and more code to many important codepaths in the
kernel.
It'd be much better to fix the race within alloc_fresh_huge_page(). That
function is pretty pathetic.
Something like this?
--- a/mm/hugetlb.c~a
+++ a/mm/hugetlb.c
@@ -105,13 +105,20 @@ static void free_huge_page(struct page *
static int alloc_fresh_huge_page(void)
{
- static int nid = 0;
+ static int prev_nid;
+ static DEFINE_SPINLOCK(nid_lock);
struct page *page;
- page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
- HUGETLB_PAGE_ORDER);
- nid = next_node(nid, node_online_map);
+ int nid;
+
+ spin_lock(&nid_lock);
+ nid = next_node(prev_nid, node_online_map);
if (nid == MAX_NUMNODES)
nid = first_node(node_online_map);
+ prev_nid = nid;
+ spin_unlock(&nid_lock);
+
+ page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
+ HUGETLB_PAGE_ORDER);
if (page) {
set_compound_page_dtor(page, free_huge_page);
spin_lock(&hugetlb_lock);
_
-
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