x86: cpa, use page pool

Switch the split page code to use the page pool. We do this
unconditionally to avoid different behaviour with and without
DEBUG_PAGEALLOC enabled.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 25 insertions, 10 deletions

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 831462c3bc35..e5d29a112d00 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -411,20 +411,29 @@ void __init cpa_init(void)
 static int split_large_page(pte_t *kpte, unsigned long address)
 {
         unsigned long flags, pfn, pfninc = 1;
-        gfp_t gfp_flags = GFP_KERNEL;
         unsigned int i, level;
         pte_t *pbase, *tmp;
         pgprot_t ref_prot;
         struct page *base;
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
-        gfp_flags = GFP_ATOMIC | __GFP_NOWARN;
-#endif
-        base = alloc_pages(gfp_flags, 0);
-        if (!base)
+        /*
+         * Get a page from the pool. The pool list is protected by the
+         * pgd_lock, which we have to take anyway for the split
+         * operation:
+         */
+        spin_lock_irqsave(&pgd_lock, flags);
+        if (list_empty(&page_pool)) {
+                spin_unlock_irqrestore(&pgd_lock, flags);
                 return -ENOMEM;
+        }
+
+        base = list_first_entry(&page_pool, struct page, lru);
+        list_del(&base->lru);
+        pool_pages--;
+
+        if (pool_pages < pool_low)
+                pool_low = pool_pages;
 
-        spin_lock_irqsave(&pgd_lock, flags);
         /*
          * Check for races, another CPU might have split this page
          * up for us already:
@@ -469,11 +478,17 @@ static int split_large_page(pte_t *kpte, unsigned long address)
         base = NULL;
 
 out_unlock:
+        /*
+         * If we dropped out via the lookup_address check under
+         * pgd_lock then stick the page back into the pool:
+         */
+        if (base) {
+                list_add(&base->lru, &page_pool);
+                pool_pages++;
+        } else
+                pool_used++;
         spin_unlock_irqrestore(&pgd_lock, flags);
 
-        if (base)
-                __free_pages(base, 0);
-
         return 0;
 }