1 files changed, 139 insertions, 53 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3e52df7..f4c43d7 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)