1 files changed, 139 insertions, 53 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3e52df7c471b..f4c43d7980ba 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -11,6 +11,8 @@
 #include <linux/highmem.h>
 #include <linux/nodemask.h>
 #include <linux/pagemap.h>
+#include <linux/mempolicy.h>
+
 #include <asm/page.h>
 #include <asm/pgtable.h>
 
@@ -36,18 +38,21 @@ static void enqueue_huge_page(struct page *page)
         free_huge_pages_node[nid]++;
 }
 
-static struct page *dequeue_huge_page(void)
+static struct page *dequeue_huge_page(struct vm_area_struct *vma,
+                                unsigned long address)
 {
         int nid = numa_node_id();
         struct page *page = NULL;
+        struct zonelist *zonelist = huge_zonelist(vma, address);
+        struct zone **z;
 
-        if (list_empty(&hugepage_freelists[nid])) {
-                for (nid = 0; nid < MAX_NUMNODES; ++nid)
-                        if (!list_empty(&hugepage_freelists[nid]))
-                                break;
+        for (z = zonelist->zones; *z; z++) {
+                nid = (*z)->zone_pgdat->node_id;
+                if (!list_empty(&hugepage_freelists[nid]))
+                        break;
         }
-        if (nid >= 0 && nid < MAX_NUMNODES &&
-            !list_empty(&hugepage_freelists[nid])) {
+
+        if (*z) {
                 page = list_entry(hugepage_freelists[nid].next,
                                   struct page, lru);
                 list_del(&page->lru);
@@ -85,13 +90,13 @@ void free_huge_page(struct page *page)
         spin_unlock(&hugetlb_lock);
 }
 
-struct page *alloc_huge_page(void)
+struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr)
 {
         struct page *page;
         int i;
 
         spin_lock(&hugetlb_lock);
-        page = dequeue_huge_page();
+        page = dequeue_huge_page(vma, addr);
         if (!page) {
                 spin_unlock(&hugetlb_lock);
                 return NULL;
@@ -194,7 +199,7 @@ static unsigned long set_max_huge_pages(unsigned long count)
         spin_lock(&hugetlb_lock);
         try_to_free_low(count);
         while (count < nr_huge_pages) {
-                struct page *page = dequeue_huge_page();
+                struct page *page = dequeue_huge_page(NULL, 0);
                 if (!page)
                         break;
                 update_and_free_page(page);
@@ -261,11 +266,12 @@ struct vm_operations_struct hugetlb_vm_ops = {
         .nopage = hugetlb_nopage,
 };
 
-static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page)
+static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
+                                int writable)
 {
         pte_t entry;
 
-        if (vma->vm_flags & VM_WRITE) {
+        if (writable) {
                 entry =
                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
         } else {
@@ -277,12 +283,27 @@ static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page)
         return entry;
 }
 
+static void set_huge_ptep_writable(struct vm_area_struct *vma,
+                                   unsigned long address, pte_t *ptep)
+{
+        pte_t entry;
+
+        entry = pte_mkwrite(pte_mkdirty(*ptep));
+        ptep_set_access_flags(vma, address, ptep, entry, 1);
+        update_mmu_cache(vma, address, entry);
+        lazy_mmu_prot_update(entry);
+}
+
+
 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
                             struct vm_area_struct *vma)
 {
         pte_t *src_pte, *dst_pte, entry;
         struct page *ptepage;
         unsigned long addr;
+        int cow;
+
+        cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 
         for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
                 src_pte = huge_pte_offset(src, addr);
@@ -294,6 +315,8 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
                 spin_lock(&dst->page_table_lock);
                 spin_lock(&src->page_table_lock);
                 if (!pte_none(*src_pte)) {
+                        if (cow)
+                                ptep_set_wrprotect(src, addr, src_pte);
                         entry = *src_pte;
                         ptepage = pte_page(entry);
                         get_page(ptepage);
@@ -345,57 +368,63 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
         flush_tlb_range(vma, start, end);
 }
 
-static struct page *find_lock_huge_page(struct address_space *mapping,
-                        unsigned long idx)
+static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
+                        unsigned long address, pte_t *ptep, pte_t pte)
 {
-        struct page *page;
-        int err;
-        struct inode *inode = mapping->host;
-        unsigned long size;
+        struct page *old_page, *new_page;
+        int i, avoidcopy;
 
-retry:
-        page = find_lock_page(mapping, idx);
-        if (page)
-                goto out;
+        old_page = pte_page(pte);
 
-        /* Check to make sure the mapping hasn't been truncated */
-        size = i_size_read(inode) >> HPAGE_SHIFT;
-        if (idx >= size)
-                goto out;
+        /* If no-one else is actually using this page, avoid the copy
+         * and just make the page writable */
+        avoidcopy = (page_count(old_page) == 1);
+        if (avoidcopy) {
+                set_huge_ptep_writable(vma, address, ptep);
+                return VM_FAULT_MINOR;
+        }
 
-        if (hugetlb_get_quota(mapping))
-                goto out;
-        page = alloc_huge_page();
-        if (!page) {
-                hugetlb_put_quota(mapping);
-                goto out;
+        page_cache_get(old_page);
+        new_page = alloc_huge_page(vma, address);
+
+        if (!new_page) {
+                page_cache_release(old_page);
+
+                /* Logically this is OOM, not a SIGBUS, but an OOM
+                 * could cause the kernel to go killing other
+                 * processes which won't help the hugepage situation
+                 * at all (?) */
+                return VM_FAULT_SIGBUS;
         }
 
-        err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
-        if (err) {
-                put_page(page);
-                hugetlb_put_quota(mapping);
-                if (err == -EEXIST)
-                        goto retry;
-                page = NULL;
+        spin_unlock(&mm->page_table_lock);
+        for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++)
+                copy_user_highpage(new_page + i, old_page + i,
+                                   address + i*PAGE_SIZE);
+        spin_lock(&mm->page_table_lock);
+
+        ptep = huge_pte_offset(mm, address & HPAGE_MASK);
+        if (likely(pte_same(*ptep, pte))) {
+                /* Break COW */
+                set_huge_pte_at(mm, address, ptep,
+                                make_huge_pte(vma, new_page, 1));
+                /* Make the old page be freed below */
+                new_page = old_page;
         }
-out:
-        return page;
+        page_cache_release(new_page);
+        page_cache_release(old_page);
+        return VM_FAULT_MINOR;
 }
 
-int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
-                        unsigned long address, int write_access)
+int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
+                        unsigned long address, pte_t *ptep, int write_access)
 {
         int ret = VM_FAULT_SIGBUS;
         unsigned long idx;
         unsigned long size;
-        pte_t *pte;
         struct page *page;
         struct address_space *mapping;
-
-        pte = huge_pte_alloc(mm, address);
-        if (!pte)
-                goto out;
+        pte_t new_pte;
 
         mapping = vma->vm_file->f_mapping;
         idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
@@ -405,9 +434,31 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
          * Use page lock to guard against racing truncation
          * before we get page_table_lock.
          */
-        page = find_lock_huge_page(mapping, idx);
-        if (!page)
-                goto out;
+retry:
+        page = find_lock_page(mapping, idx);
+        if (!page) {
+                if (hugetlb_get_quota(mapping))
+                        goto out;
+                page = alloc_huge_page(vma, address);
+                if (!page) {
+                        hugetlb_put_quota(mapping);
+                        goto out;
+                }
+
+                if (vma->vm_flags & VM_SHARED) {
+                        int err;
+
+                        err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
+                        if (err) {
+                                put_page(page);
+                                hugetlb_put_quota(mapping);
+                                if (err == -EEXIST)
+                                        goto retry;
+                                goto out;
+                        }
+                } else
+                        lock_page(page);
+        }
 
         spin_lock(&mm->page_table_lock);
         size = i_size_read(mapping->host) >> HPAGE_SHIFT;
@@ -415,11 +466,19 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                 goto backout;
 
         ret = VM_FAULT_MINOR;
-        if (!pte_none(*pte))
+        if (!pte_none(*ptep))
                 goto backout;
 
         add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
-        set_huge_pte_at(mm, address, pte, make_huge_pte(vma, page));
+        new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
+                                && (vma->vm_flags & VM_SHARED)));
+        set_huge_pte_at(mm, address, ptep, new_pte);
+
+        if (write_access && !(vma->vm_flags & VM_SHARED)) {
+                /* Optimization, do the COW without a second fault */
+                ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
+        }
+
         spin_unlock(&mm->page_table_lock);
         unlock_page(page);
 out:
@@ -433,6 +492,33 @@ backout:
         goto out;
 }
 
+int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+                        unsigned long address, int write_access)
+{
+        pte_t *ptep;
+        pte_t entry;
+        int ret;
+
+        ptep = huge_pte_alloc(mm, address);
+        if (!ptep)
+                return VM_FAULT_OOM;
+
+        entry = *ptep;
+        if (pte_none(entry))
+                return hugetlb_no_page(mm, vma, address, ptep, write_access);
+
+        ret = VM_FAULT_MINOR;
+
+        spin_lock(&mm->page_table_lock);
+        /* Check for a racing update before calling hugetlb_cow */
+        if (likely(pte_same(entry, *ptep)))
+                if (write_access && !pte_write(entry))
+                        ret = hugetlb_cow(mm, vma, address, ptep, entry);
+        spin_unlock(&mm->page_table_lock);
+
+        return ret;
+}
+
 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
                         struct page **pages, struct vm_area_struct **vmas,
                         unsigned long *position, int *length, int i)