x86: ensure percpu lpage doesn't consume too much vmalloc space

On extreme configuration (e.g. 32bit 32-way NUMA machine), lpage
percpu first chunk allocator can consume too much of vmalloc space.
Make it fall back to 4k allocator if the consumption goes over 20%.

[ Impact: add sanity check for lpage percpu first chunk allocator ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jan Beulich <JBeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>

1 files changed, 15 insertions, 3 deletions

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 165ebd5ba83b..29a3eef7cf4a 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -163,9 +163,21 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
         int i, j;
         ssize_t ret;
 
-        /* on non-NUMA, embedding is better */
-        if (!chosen && !pcpu_need_numa())
-                return -EINVAL;
+        if (!chosen) {
+                size_t vm_size = VMALLOC_END - VMALLOC_START;
+                size_t tot_size = num_possible_cpus() * PMD_SIZE;
+
+                /* on non-NUMA, embedding is better */
+                if (!pcpu_need_numa())
+                        return -EINVAL;
+
+                /* don't consume more than 20% of vmalloc area */
+                if (tot_size > vm_size / 5) {
+                        pr_info("PERCPU: too large chunk size %zuMB for "
+                                "large page remap\n", tot_size >> 20);
+                        return -EINVAL;
+                }
+        }
 
         /* need PSE */
         if (!cpu_has_pse) {