1 files changed, 254 insertions, 209 deletions

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 43e2f8483e4f..a9ec89c3fbca 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -25,15 +25,27 @@
  * The current flushing context - we pass it instead of 5 arguments:
  */
 struct cpa_data {
-        unsigned long   vaddr;
+        unsigned long   *vaddr;
         pgprot_t        mask_set;
         pgprot_t        mask_clr;
         int             numpages;
-        int             flushtlb;
+        int             flags;
         unsigned long   pfn;
         unsigned        force_split : 1;
+        int             curpage;
 };
 
+/*
+ * Serialize cpa() (for !DEBUG_PAGEALLOC which uses large identity mappings)
+ * using cpa_lock. So that we don't allow any other cpu, with stale large tlb
+ * entries change the page attribute in parallel to some other cpu
+ * splitting a large page entry along with changing the attribute.
+ */
+static DEFINE_SPINLOCK(cpa_lock);
+
+#define CPA_FLUSHTLB 1
+#define CPA_ARRAY 2
+
 #ifdef CONFIG_PROC_FS
 static unsigned long direct_pages_count[PG_LEVEL_NUM];
 
@@ -84,7 +96,7 @@ static inline unsigned long highmap_start_pfn(void)
 
 static inline unsigned long highmap_end_pfn(void)
 {
-        return __pa(round_up((unsigned long)_end, PMD_SIZE)) >> PAGE_SHIFT;
+        return __pa(roundup((unsigned long)_end, PMD_SIZE)) >> PAGE_SHIFT;
 }
 
 #endif
@@ -190,6 +202,41 @@ static void cpa_flush_range(unsigned long start, int numpages, int cache)
         }
 }
 
+static void cpa_flush_array(unsigned long *start, int numpages, int cache)
+{
+        unsigned int i, level;
+        unsigned long *addr;
+
+        BUG_ON(irqs_disabled());
+
+        on_each_cpu(__cpa_flush_range, NULL, 1);
+
+        if (!cache)
+                return;
+
+        /* 4M threshold */
+        if (numpages >= 1024) {
+                if (boot_cpu_data.x86_model >= 4)
+                        wbinvd();
+                return;
+        }
+        /*
+         * We only need to flush on one CPU,
+         * clflush is a MESI-coherent instruction that
+         * will cause all other CPUs to flush the same
+         * cachelines:
+         */
+        for (i = 0, addr = start; i < numpages; i++, addr++) {
+                pte_t *pte = lookup_address(*addr, &level);
+
+                /*
+                 * Only flush present addresses:
+                 */
+                if (pte && (pte_val(*pte) & _PAGE_PRESENT))
+                        clflush_cache_range((void *) *addr, PAGE_SIZE);
+        }
+}
+
 /*
  * Certain areas of memory on x86 require very specific protection flags,
  * for example the BIOS area or kernel text. Callers don't always get this
@@ -398,7 +445,7 @@ try_preserve_large_page(pte_t *kpte, unsigned long address,
                  */
                 new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot));
                 __set_pmd_pte(kpte, address, new_pte);
-                cpa->flushtlb = 1;
+                cpa->flags |= CPA_FLUSHTLB;
                 do_split = 0;
         }
 
@@ -408,84 +455,6 @@ out_unlock:
         return do_split;
 }
 
-static LIST_HEAD(page_pool);
-static unsigned long pool_size, pool_pages, pool_low;
-static unsigned long pool_used, pool_failed;
-
-static void cpa_fill_pool(struct page **ret)
-{
-        gfp_t gfp = GFP_KERNEL;
-        unsigned long flags;
-        struct page *p;
-
-        /*
-         * Avoid recursion (on debug-pagealloc) and also signal
-         * our priority to get to these pagetables:
-         */
-        if (current->flags & PF_MEMALLOC)
-                return;
-        current->flags |= PF_MEMALLOC;
-
-        /*
-         * Allocate atomically from atomic contexts:
-         */
-        if (in_atomic() || irqs_disabled() || debug_pagealloc)
-                gfp =  GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN;
-
-        while (pool_pages < pool_size || (ret && !*ret)) {
-                p = alloc_pages(gfp, 0);
-                if (!p) {
-                        pool_failed++;
-                        break;
-                }
-                /*
-                 * If the call site needs a page right now, provide it:
-                 */
-                if (ret && !*ret) {
-                        *ret = p;
-                        continue;
-                }
-                spin_lock_irqsave(&pgd_lock, flags);
-                list_add(&p->lru, &page_pool);
-                pool_pages++;
-                spin_unlock_irqrestore(&pgd_lock, flags);
-        }
-
-        current->flags &= ~PF_MEMALLOC;
-}
-
-#define SHIFT_MB                (20 - PAGE_SHIFT)
-#define ROUND_MB_GB             ((1 << 10) - 1)
-#define SHIFT_MB_GB             10
-#define POOL_PAGES_PER_GB       16
-
-void __init cpa_init(void)
-{
-        struct sysinfo si;
-        unsigned long gb;
-
-        si_meminfo(&si);
-        /*
-         * Calculate the number of pool pages:
-         *
-         * Convert totalram (nr of pages) to MiB and round to the next
-         * GiB. Shift MiB to Gib and multiply the result by
-         * POOL_PAGES_PER_GB:
-         */
-        if (debug_pagealloc) {
-                gb = ((si.totalram >> SHIFT_MB) + ROUND_MB_GB) >> SHIFT_MB_GB;
-                pool_size = POOL_PAGES_PER_GB * gb;
-        } else {
-                pool_size = 1;
-        }
-        pool_low = pool_size;
-
-        cpa_fill_pool(NULL);
-        printk(KERN_DEBUG
-               "CPA: page pool initialized %lu of %lu pages preallocated\n",
-               pool_pages, pool_size);
-}
-
 static int split_large_page(pte_t *kpte, unsigned long address)
 {
         unsigned long flags, pfn, pfninc = 1;
@@ -494,28 +463,15 @@ static int split_large_page(pte_t *kpte, unsigned long address)
         pgprot_t ref_prot;
         struct page *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);
-                base = NULL;
-                cpa_fill_pool(&base);
-                if (!base)
-                        return -ENOMEM;
-                spin_lock_irqsave(&pgd_lock, flags);
-        } else {
-                base = list_first_entry(&page_pool, struct page, lru);
-                list_del(&base->lru);
-                pool_pages--;
-
-                if (pool_pages < pool_low)
-                        pool_low = pool_pages;
-        }
+        if (!debug_pagealloc)
+                spin_unlock(&cpa_lock);
+        base = alloc_pages(GFP_KERNEL, 0);
+        if (!debug_pagealloc)
+                spin_lock(&cpa_lock);
+        if (!base)
+                return -ENOMEM;
 
+        spin_lock_irqsave(&pgd_lock, flags);
         /*
          * Check for races, another CPU might have split this page
          * up for us already:
@@ -572,11 +528,8 @@ 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++;
+        if (base)
+                __free_page(base);
         spin_unlock_irqrestore(&pgd_lock, flags);
 
         return 0;
@@ -584,11 +537,16 @@ out_unlock:
 
 static int __change_page_attr(struct cpa_data *cpa, int primary)
 {
-        unsigned long address = cpa->vaddr;
+        unsigned long address;
         int do_split, err;
         unsigned int level;
         pte_t *kpte, old_pte;
 
+        if (cpa->flags & CPA_ARRAY)
+                address = cpa->vaddr[cpa->curpage];
+        else
+                address = *cpa->vaddr;
+
 repeat:
         kpte = lookup_address(address, &level);
         if (!kpte)
@@ -600,7 +558,7 @@ repeat:
                         return 0;
                 WARN(1, KERN_WARNING "CPA: called for zero pte. "
                        "vaddr = %lx cpa->vaddr = %lx\n", address,
-                       cpa->vaddr);
+                       *cpa->vaddr);
                 return -EINVAL;
         }
 
@@ -626,7 +584,7 @@ repeat:
                  */
                 if (pte_val(old_pte) != pte_val(new_pte)) {
                         set_pte_atomic(kpte, new_pte);
-                        cpa->flushtlb = 1;
+                        cpa->flags |= CPA_FLUSHTLB;
                 }
                 cpa->numpages = 1;
                 return 0;
@@ -650,7 +608,25 @@ repeat:
          */
         err = split_large_page(kpte, address);
         if (!err) {
-                cpa->flushtlb = 1;
+                /*
+                 * Do a global flush tlb after splitting the large page
+                 * and before we do the actual change page attribute in the PTE.
+                 *
+                 * With out this, we violate the TLB application note, that says
+                 * "The TLBs may contain both ordinary and large-page
+                 *  translations for a 4-KByte range of linear addresses. This
+                 *  may occur if software modifies the paging structures so that
+                 *  the page size used for the address range changes. If the two
+                 *  translations differ with respect to page frame or attributes
+                 *  (e.g., permissions), processor behavior is undefined and may
+                 *  be implementation-specific."
+                 *
+                 * We do this global tlb flush inside the cpa_lock, so that we
+                 * don't allow any other cpu, with stale tlb entries change the
+                 * page attribute in parallel, that also falls into the
+                 * just split large page entry.
+                 */
+                flush_tlb_all();
                 goto repeat;
         }
 
@@ -663,6 +639,7 @@ static int cpa_process_alias(struct cpa_data *cpa)
 {
         struct cpa_data alias_cpa;
         int ret = 0;
+        unsigned long temp_cpa_vaddr, vaddr;
 
         if (cpa->pfn >= max_pfn_mapped)
                 return 0;
@@ -675,16 +652,24 @@ static int cpa_process_alias(struct cpa_data *cpa)
          * No need to redo, when the primary call touched the direct
          * mapping already:
          */
-        if (!(within(cpa->vaddr, PAGE_OFFSET,
+        if (cpa->flags & CPA_ARRAY)
+                vaddr = cpa->vaddr[cpa->curpage];
+        else
+                vaddr = *cpa->vaddr;
+
+        if (!(within(vaddr, PAGE_OFFSET,
                     PAGE_OFFSET + (max_low_pfn_mapped << PAGE_SHIFT))
 #ifdef CONFIG_X86_64
-                || within(cpa->vaddr, PAGE_OFFSET + (1UL<<32),
+                || within(vaddr, PAGE_OFFSET + (1UL<<32),
                     PAGE_OFFSET + (max_pfn_mapped << PAGE_SHIFT))
 #endif
         )) {
 
                 alias_cpa = *cpa;
-                alias_cpa.vaddr = (unsigned long) __va(cpa->pfn << PAGE_SHIFT);
+                temp_cpa_vaddr = (unsigned long) __va(cpa->pfn << PAGE_SHIFT);
+                alias_cpa.vaddr = &temp_cpa_vaddr;
+                alias_cpa.flags &= ~CPA_ARRAY;
+
 
                 ret = __change_page_attr_set_clr(&alias_cpa, 0);
         }
@@ -696,7 +681,7 @@ static int cpa_process_alias(struct cpa_data *cpa)
          * No need to redo, when the primary call touched the high
          * mapping already:
          */
-        if (within(cpa->vaddr, (unsigned long) _text, (unsigned long) _end))
+        if (within(vaddr, (unsigned long) _text, (unsigned long) _end))
                 return 0;
 
         /*
@@ -707,8 +692,9 @@ static int cpa_process_alias(struct cpa_data *cpa)
                 return 0;
 
         alias_cpa = *cpa;
-        alias_cpa.vaddr =
-                (cpa->pfn << PAGE_SHIFT) + __START_KERNEL_map - phys_base;
+        temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) + __START_KERNEL_map - phys_base;
+        alias_cpa.vaddr = &temp_cpa_vaddr;
+        alias_cpa.flags &= ~CPA_ARRAY;
 
         /*
          * The high mapping range is imprecise, so ignore the return value.
@@ -728,8 +714,15 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
                  * preservation check.
                  */
                 cpa->numpages = numpages;
+                /* for array changes, we can't use large page */
+                if (cpa->flags & CPA_ARRAY)
+                        cpa->numpages = 1;
 
+                if (!debug_pagealloc)
+                        spin_lock(&cpa_lock);
                 ret = __change_page_attr(cpa, checkalias);
+                if (!debug_pagealloc)
+                        spin_unlock(&cpa_lock);
                 if (ret)
                         return ret;
 
@@ -746,7 +739,11 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
                  */
                 BUG_ON(cpa->numpages > numpages);
                 numpages -= cpa->numpages;
-                cpa->vaddr += cpa->numpages * PAGE_SIZE;
+                if (cpa->flags & CPA_ARRAY)
+                        cpa->curpage++;
+                else
+                        *cpa->vaddr += cpa->numpages * PAGE_SIZE;
+
         }
         return 0;
 }
@@ -757,9 +754,9 @@ static inline int cache_attr(pgprot_t attr)
                 (_PAGE_PAT | _PAGE_PAT_LARGE | _PAGE_PWT | _PAGE_PCD);
 }
 
-static int change_page_attr_set_clr(unsigned long addr, int numpages,
+static int change_page_attr_set_clr(unsigned long *addr, int numpages,
                                     pgprot_t mask_set, pgprot_t mask_clr,
-                                    int force_split)
+                                    int force_split, int array)
 {
         struct cpa_data cpa;
         int ret, cache, checkalias;
@@ -774,21 +771,38 @@ static int change_page_attr_set_clr(unsigned long addr, int numpages,
                 return 0;
 
         /* Ensure we are PAGE_SIZE aligned */
-        if (addr & ~PAGE_MASK) {
-                addr &= PAGE_MASK;
-                /*
-                 * People should not be passing in unaligned addresses:
-                 */
-                WARN_ON_ONCE(1);
+        if (!array) {
+                if (*addr & ~PAGE_MASK) {
+                        *addr &= PAGE_MASK;
+                        /*
+                         * People should not be passing in unaligned addresses:
+                         */
+                        WARN_ON_ONCE(1);
+                }
+        } else {
+                int i;
+                for (i = 0; i < numpages; i++) {
+                        if (addr[i] & ~PAGE_MASK) {
+                                addr[i] &= PAGE_MASK;
+                                WARN_ON_ONCE(1);
+                        }
+                }
         }
 
+        /* Must avoid aliasing mappings in the highmem code */
+        kmap_flush_unused();
+
         cpa.vaddr = addr;
         cpa.numpages = numpages;
         cpa.mask_set = mask_set;
         cpa.mask_clr = mask_clr;
-        cpa.flushtlb = 0;
+        cpa.flags = 0;
+        cpa.curpage = 0;
         cpa.force_split = force_split;
 
+        if (array)
+                cpa.flags |= CPA_ARRAY;
+
         /* No alias checking for _NX bit modifications */
         checkalias = (pgprot_val(mask_set) | pgprot_val(mask_clr)) != _PAGE_NX;
 
@@ -797,7 +811,7 @@ static int change_page_attr_set_clr(unsigned long addr, int numpages,
         /*
          * Check whether we really changed something:
          */
-        if (!cpa.flushtlb)
+        if (!(cpa.flags & CPA_FLUSHTLB))
                 goto out;
 
         /*
@@ -812,27 +826,30 @@ static int change_page_attr_set_clr(unsigned long addr, int numpages,
          * error case we fall back to cpa_flush_all (which uses
          * wbindv):
          */
-        if (!ret && cpu_has_clflush)
-                cpa_flush_range(addr, numpages, cache);
-        else
+        if (!ret && cpu_has_clflush) {
+                if (cpa.flags & CPA_ARRAY)
+                        cpa_flush_array(addr, numpages, cache);
+                else
+                        cpa_flush_range(*addr, numpages, cache);
+        } else
                 cpa_flush_all(cache);
 
 out:
-        cpa_fill_pool(NULL);
-
         return ret;
 }
 
-static inline int change_page_attr_set(unsigned long addr, int numpages,
-                                       pgprot_t mask)
+static inline int change_page_attr_set(unsigned long *addr, int numpages,
+                                       pgprot_t mask, int array)
 {
-        return change_page_attr_set_clr(addr, numpages, mask, __pgprot(0), 0);
+        return change_page_attr_set_clr(addr, numpages, mask, __pgprot(0), 0,
+                array);
 }
 
-static inline int change_page_attr_clear(unsigned long addr, int numpages,
-                                         pgprot_t mask)
+static inline int change_page_attr_clear(unsigned long *addr, int numpages,
+                                         pgprot_t mask, int array)
 {
-        return change_page_attr_set_clr(addr, numpages, __pgprot(0), mask, 0);
+        return change_page_attr_set_clr(addr, numpages, __pgprot(0), mask, 0,
+                array);
 }
 
 int _set_memory_uc(unsigned long addr, int numpages)
@@ -840,8 +857,8 @@ int _set_memory_uc(unsigned long addr, int numpages)
         /*
          * for now UC MINUS. see comments in ioremap_nocache()
          */
-        return change_page_attr_set(addr, numpages,
-                                    __pgprot(_PAGE_CACHE_UC_MINUS));
+        return change_page_attr_set(&addr, numpages,
+                                    __pgprot(_PAGE_CACHE_UC_MINUS), 0);
 }
 
 int set_memory_uc(unsigned long addr, int numpages)
@@ -857,10 +874,48 @@ int set_memory_uc(unsigned long addr, int numpages)
 }
 EXPORT_SYMBOL(set_memory_uc);
 
+int set_memory_array_uc(unsigned long *addr, int addrinarray)
+{
+        unsigned long start;
+        unsigned long end;
+        int i;
+        /*
+         * for now UC MINUS. see comments in ioremap_nocache()
+         */
+        for (i = 0; i < addrinarray; i++) {
+                start = __pa(addr[i]);
+                for (end = start + PAGE_SIZE; i < addrinarray - 1; end += PAGE_SIZE) {
+                        if (end != __pa(addr[i + 1]))
+                                break;
+                        i++;
+                }
+                if (reserve_memtype(start, end, _PAGE_CACHE_UC_MINUS, NULL))
+                        goto out;
+        }
+
+        return change_page_attr_set(addr, addrinarray,
+                                    __pgprot(_PAGE_CACHE_UC_MINUS), 1);
+out:
+        for (i = 0; i < addrinarray; i++) {
+                unsigned long tmp = __pa(addr[i]);
+
+                if (tmp == start)
+                        break;
+                for (end = tmp + PAGE_SIZE; i < addrinarray - 1; end += PAGE_SIZE) {
+                        if (end != __pa(addr[i + 1]))
+                                break;
+                        i++;
+                }
+                free_memtype(tmp, end);
+        }
+        return -EINVAL;
+}
+EXPORT_SYMBOL(set_memory_array_uc);
+
 int _set_memory_wc(unsigned long addr, int numpages)
 {
-        return change_page_attr_set(addr, numpages,
-                                    __pgprot(_PAGE_CACHE_WC));
+        return change_page_attr_set(&addr, numpages,
+                                    __pgprot(_PAGE_CACHE_WC), 0);
 }
 
 int set_memory_wc(unsigned long addr, int numpages)
@@ -878,8 +933,8 @@ EXPORT_SYMBOL(set_memory_wc);
 
 int _set_memory_wb(unsigned long addr, int numpages)
 {
-        return change_page_attr_clear(addr, numpages,
-                                      __pgprot(_PAGE_CACHE_MASK));
+        return change_page_attr_clear(&addr, numpages,
+                                      __pgprot(_PAGE_CACHE_MASK), 0);
 }
 
 int set_memory_wb(unsigned long addr, int numpages)
@@ -890,37 +945,59 @@ int set_memory_wb(unsigned long addr, int numpages)
 }
 EXPORT_SYMBOL(set_memory_wb);
 
+int set_memory_array_wb(unsigned long *addr, int addrinarray)
+{
+        int i;
+
+        for (i = 0; i < addrinarray; i++) {
+                unsigned long start = __pa(addr[i]);
+                unsigned long end;
+
+                for (end = start + PAGE_SIZE; i < addrinarray - 1; end += PAGE_SIZE) {
+                        if (end != __pa(addr[i + 1]))
+                                break;
+                        i++;
+                }
+                free_memtype(start, end);
+        }
+        return change_page_attr_clear(addr, addrinarray,
+                                      __pgprot(_PAGE_CACHE_MASK), 1);
+}
+EXPORT_SYMBOL(set_memory_array_wb);
+
 int set_memory_x(unsigned long addr, int numpages)
 {
-        return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_NX));
+        return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_NX), 0);
 }
 EXPORT_SYMBOL(set_memory_x);
 
 int set_memory_nx(unsigned long addr, int numpages)
 {
-        return change_page_attr_set(addr, numpages, __pgprot(_PAGE_NX));
+        return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_NX), 0);
 }
 EXPORT_SYMBOL(set_memory_nx);
 
 int set_memory_ro(unsigned long addr, int numpages)
 {
-        return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_RW));
+        return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_RW), 0);
 }
+EXPORT_SYMBOL_GPL(set_memory_ro);
 
 int set_memory_rw(unsigned long addr, int numpages)
 {
-        return change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
+        return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_RW), 0);
 }
+EXPORT_SYMBOL_GPL(set_memory_rw);
 
 int set_memory_np(unsigned long addr, int numpages)
 {
-        return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_PRESENT));
+        return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_PRESENT), 0);
 }
 
 int set_memory_4k(unsigned long addr, int numpages)
 {
-        return change_page_attr_set_clr(addr, numpages, __pgprot(0),
-                                        __pgprot(0), 1);
+        return change_page_attr_set_clr(&addr, numpages, __pgprot(0),
+                                        __pgprot(0), 1, 0);
 }
 
 int set_pages_uc(struct page *page, int numpages)
@@ -973,22 +1050,38 @@ int set_pages_rw(struct page *page, int numpages)
 
 static int __set_pages_p(struct page *page, int numpages)
 {
-        struct cpa_data cpa = { .vaddr = (unsigned long) page_address(page),
+        unsigned long tempaddr = (unsigned long) page_address(page);
+        struct cpa_data cpa = { .vaddr = &tempaddr,
                                 .numpages = numpages,
                                 .mask_set = __pgprot(_PAGE_PRESENT | _PAGE_RW),
-                                .mask_clr = __pgprot(0)};
+                                .mask_clr = __pgprot(0),
+                                .flags = 0};
 
-        return __change_page_attr_set_clr(&cpa, 1);
+        /*
+         * No alias checking needed for setting present flag. otherwise,
+         * we may need to break large pages for 64-bit kernel text
+         * mappings (this adds to complexity if we want to do this from
+         * atomic context especially). Let's keep it simple!
+         */
+        return __change_page_attr_set_clr(&cpa, 0);
 }
 
 static int __set_pages_np(struct page *page, int numpages)
 {
-        struct cpa_data cpa = { .vaddr = (unsigned long) page_address(page),
+        unsigned long tempaddr = (unsigned long) page_address(page);
+        struct cpa_data cpa = { .vaddr = &tempaddr,
                                 .numpages = numpages,
                                 .mask_set = __pgprot(0),
-                                .mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW)};
+                                .mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW),
+                                .flags = 0};
 
-        return __change_page_attr_set_clr(&cpa, 1);
+        /*
+         * No alias checking needed for setting not present flag. otherwise,
+         * we may need to break large pages for 64-bit kernel text
+         * mappings (this adds to complexity if we want to do this from
+         * atomic context especially). Let's keep it simple!
+         */
+        return __change_page_attr_set_clr(&cpa, 0);
 }
 
 void kernel_map_pages(struct page *page, int numpages, int enable)
@@ -1008,11 +1101,8 @@ void kernel_map_pages(struct page *page, int numpages, int enable)
 
         /*
          * The return value is ignored as the calls cannot fail.
-         * Large pages are kept enabled at boot time, and are
-         * split up quickly with DEBUG_PAGEALLOC. If a splitup
-         * fails here (due to temporary memory shortage) no damage
-         * is done because we just keep the largepage intact up
-         * to the next attempt when it will likely be split up:
+         * Large pages for identity mappings are not used at boot time
+         * and hence no memory allocations during large page split.
          */
         if (enable)
                 __set_pages_p(page, numpages);
@@ -1024,53 +1114,8 @@ void kernel_map_pages(struct page *page, int numpages, int enable)
          * but that can deadlock->flush only current cpu:
          */
         __flush_tlb_all();
-
-        /*
-         * Try to refill the page pool here. We can do this only after
-         * the tlb flush.
-         */
-        cpa_fill_pool(NULL);
 }
 
-#ifdef CONFIG_DEBUG_FS
-static int dpa_show(struct seq_file *m, void *v)
-{
-        seq_puts(m, "DEBUG_PAGEALLOC\n");
-        seq_printf(m, "pool_size     : %lu\n", pool_size);
-        seq_printf(m, "pool_pages    : %lu\n", pool_pages);
-        seq_printf(m, "pool_low      : %lu\n", pool_low);
-        seq_printf(m, "pool_used     : %lu\n", pool_used);
-        seq_printf(m, "pool_failed   : %lu\n", pool_failed);
-
-        return 0;
-}
-
-static int dpa_open(struct inode *inode, struct file *filp)
-{
-        return single_open(filp, dpa_show, NULL);
-}
-
-static const struct file_operations dpa_fops = {
-        .open           = dpa_open,
-        .read           = seq_read,
-        .llseek         = seq_lseek,
-        .release        = single_release,
-};
-
-static int __init debug_pagealloc_proc_init(void)
-{
-        struct dentry *de;
-
-        de = debugfs_create_file("debug_pagealloc", 0600, NULL, NULL,
-                                 &dpa_fops);
-        if (!de)
-                return -ENOMEM;
-
-        return 0;
-}
-__initcall(debug_pagealloc_proc_init);
-#endif
-
 #ifdef CONFIG_HIBERNATION
 
 bool kernel_page_present(struct page *page)