1 files changed, 398 insertions, 1 deletions

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index bcafd9d7639c..f68e216600b9 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -10,9 +10,31 @@
  */
 #define pr_fmt(fmt)	"HugeTLB: " fmt
 
-#include <linux/memory.h>
+#include <linux/pgtable.h>
+#include <linux/bootmem_info.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
 #include "hugetlb_vmemmap.h"
 
+/**
+ * struct vmemmap_remap_walk - walk vmemmap page table
+ *
+ * @remap_pte:		called for each lowest-level entry (PTE).
+ * @nr_walked:		the number of walked pte.
+ * @reuse_page:		the page which is reused for the tail vmemmap pages.
+ * @reuse_addr:		the virtual address of the @reuse_page page.
+ * @vmemmap_pages:	the list head of the vmemmap pages that can be freed
+ *			or is mapped from.
+ */
+struct vmemmap_remap_walk {
+	void			(*remap_pte)(pte_t *pte, unsigned long addr,
+					     struct vmemmap_remap_walk *walk);
+	unsigned long		nr_walked;
+	struct page		*reuse_page;
+	unsigned long		reuse_addr;
+	struct list_head	*vmemmap_pages;
+};
+
 /*
  * There are a lot of struct page structures associated with each HugeTLB page.
  * For tail pages, the value of compound_head is the same. So we can reuse first
@@ -23,6 +45,381 @@
 #define RESERVE_VMEMMAP_NR		1U
 #define RESERVE_VMEMMAP_SIZE		(RESERVE_VMEMMAP_NR << PAGE_SHIFT)
 
+static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
+{
+	pmd_t __pmd;
+	int i;
+	unsigned long addr = start;
+	struct page *page = pmd_page(*pmd);
+	pte_t *pgtable = pte_alloc_one_kernel(&init_mm);
+
+	if (!pgtable)
+		return -ENOMEM;
+
+	pmd_populate_kernel(&init_mm, &__pmd, pgtable);
+
+	for (i = 0; i < PMD_SIZE / PAGE_SIZE; i++, addr += PAGE_SIZE) {
+		pte_t entry, *pte;
+		pgprot_t pgprot = PAGE_KERNEL;
+
+		entry = mk_pte(page + i, pgprot);
+		pte = pte_offset_kernel(&__pmd, addr);
+		set_pte_at(&init_mm, addr, pte, entry);
+	}
+
+	spin_lock(&init_mm.page_table_lock);
+	if (likely(pmd_leaf(*pmd))) {
+		/*
+		 * Higher order allocations from buddy allocator must be able to
+		 * be treated as indepdenent small pages (as they can be freed
+		 * individually).
+		 */
+		if (!PageReserved(page))
+			split_page(page, get_order(PMD_SIZE));
+
+		/* Make pte visible before pmd. See comment in pmd_install(). */
+		smp_wmb();
+		pmd_populate_kernel(&init_mm, pmd, pgtable);
+		flush_tlb_kernel_range(start, start + PMD_SIZE);
+	} else {
+		pte_free_kernel(&init_mm, pgtable);
+	}
+	spin_unlock(&init_mm.page_table_lock);
+
+	return 0;
+}
+
+static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
+{
+	int leaf;
+
+	spin_lock(&init_mm.page_table_lock);
+	leaf = pmd_leaf(*pmd);
+	spin_unlock(&init_mm.page_table_lock);
+
+	if (!leaf)
+		return 0;
+
+	return __split_vmemmap_huge_pmd(pmd, start);
+}
+
+static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr,
+			      unsigned long end,
+			      struct vmemmap_remap_walk *walk)
+{
+	pte_t *pte = pte_offset_kernel(pmd, addr);
+
+	/*
+	 * The reuse_page is found 'first' in table walk before we start
+	 * remapping (which is calling @walk->remap_pte).
+	 */
+	if (!walk->reuse_page) {
+		walk->reuse_page = pte_page(*pte);
+		/*
+		 * Because the reuse address is part of the range that we are
+		 * walking, skip the reuse address range.
+		 */
+		addr += PAGE_SIZE;
+		pte++;
+		walk->nr_walked++;
+	}
+
+	for (; addr != end; addr += PAGE_SIZE, pte++) {
+		walk->remap_pte(pte, addr, walk);
+		walk->nr_walked++;
+	}
+}
+
+static int vmemmap_pmd_range(pud_t *pud, unsigned long addr,
+			     unsigned long end,
+			     struct vmemmap_remap_walk *walk)
+{
+	pmd_t *pmd;
+	unsigned long next;
+
+	pmd = pmd_offset(pud, addr);
+	do {
+		int ret;
+
+		ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK);
+		if (ret)
+			return ret;
+
+		next = pmd_addr_end(addr, end);
+		vmemmap_pte_range(pmd, addr, next, walk);
+	} while (pmd++, addr = next, addr != end);
+
+	return 0;
+}
+
+static int vmemmap_pud_range(p4d_t *p4d, unsigned long addr,
+			     unsigned long end,
+			     struct vmemmap_remap_walk *walk)
+{
+	pud_t *pud;
+	unsigned long next;
+
+	pud = pud_offset(p4d, addr);
+	do {
+		int ret;
+
+		next = pud_addr_end(addr, end);
+		ret = vmemmap_pmd_range(pud, addr, next, walk);
+		if (ret)
+			return ret;
+	} while (pud++, addr = next, addr != end);
+
+	return 0;
+}
+
+static int vmemmap_p4d_range(pgd_t *pgd, unsigned long addr,
+			     unsigned long end,
+			     struct vmemmap_remap_walk *walk)
+{
+	p4d_t *p4d;
+	unsigned long next;
+
+	p4d = p4d_offset(pgd, addr);
+	do {
+		int ret;
+
+		next = p4d_addr_end(addr, end);
+		ret = vmemmap_pud_range(p4d, addr, next, walk);
+		if (ret)
+			return ret;
+	} while (p4d++, addr = next, addr != end);
+
+	return 0;
+}
+
+static int vmemmap_remap_range(unsigned long start, unsigned long end,
+			       struct vmemmap_remap_walk *walk)
+{
+	unsigned long addr = start;
+	unsigned long next;
+	pgd_t *pgd;
+
+	VM_BUG_ON(!PAGE_ALIGNED(start));
+	VM_BUG_ON(!PAGE_ALIGNED(end));
+
+	pgd = pgd_offset_k(addr);
+	do {
+		int ret;
+
+		next = pgd_addr_end(addr, end);
+		ret = vmemmap_p4d_range(pgd, addr, next, walk);
+		if (ret)
+			return ret;
+	} while (pgd++, addr = next, addr != end);
+
+	/*
+	 * We only change the mapping of the vmemmap virtual address range
+	 * [@start + PAGE_SIZE, end), so we only need to flush the TLB which
+	 * belongs to the range.
+	 */
+	flush_tlb_kernel_range(start + PAGE_SIZE, end);
+
+	return 0;
+}
+
+/*
+ * Free a vmemmap page. A vmemmap page can be allocated from the memblock
+ * allocator or buddy allocator. If the PG_reserved flag is set, it means
+ * that it allocated from the memblock allocator, just free it via the
+ * free_bootmem_page(). Otherwise, use __free_page().
+ */
+static inline void free_vmemmap_page(struct page *page)
+{
+	if (PageReserved(page))
+		free_bootmem_page(page);
+	else
+		__free_page(page);
+}
+
+/* Free a list of the vmemmap pages */
+static void free_vmemmap_page_list(struct list_head *list)
+{
+	struct page *page, *next;
+
+	list_for_each_entry_safe(page, next, list, lru) {
+		list_del(&page->lru);
+		free_vmemmap_page(page);
+	}
+}
+
+static void vmemmap_remap_pte(pte_t *pte, unsigned long addr,
+			      struct vmemmap_remap_walk *walk)
+{
+	/*
+	 * Remap the tail pages as read-only to catch illegal write operation
+	 * to the tail pages.
+	 */
+	pgprot_t pgprot = PAGE_KERNEL_RO;
+	pte_t entry = mk_pte(walk->reuse_page, pgprot);
+	struct page *page = pte_page(*pte);
+
+	list_add_tail(&page->lru, walk->vmemmap_pages);
+	set_pte_at(&init_mm, addr, pte, entry);
+}
+
+/*
+ * How many struct page structs need to be reset. When we reuse the head
+ * struct page, the special metadata (e.g. page->flags or page->mapping)
+ * cannot copy to the tail struct page structs. The invalid value will be
+ * checked in the free_tail_pages_check(). In order to avoid the message
+ * of "corrupted mapping in tail page". We need to reset at least 3 (one
+ * head struct page struct and two tail struct page structs) struct page
+ * structs.
+ */
+#define NR_RESET_STRUCT_PAGE		3
+
+static inline void reset_struct_pages(struct page *start)
+{
+	int i;
+	struct page *from = start + NR_RESET_STRUCT_PAGE;
+
+	for (i = 0; i < NR_RESET_STRUCT_PAGE; i++)
+		memcpy(start + i, from, sizeof(*from));
+}
+
+static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
+				struct vmemmap_remap_walk *walk)
+{
+	pgprot_t pgprot = PAGE_KERNEL;
+	struct page *page;
+	void *to;
+
+	BUG_ON(pte_page(*pte) != walk->reuse_page);
+
+	page = list_first_entry(walk->vmemmap_pages, struct page, lru);
+	list_del(&page->lru);
+	to = page_to_virt(page);
+	copy_page(to, (void *)walk->reuse_addr);
+	reset_struct_pages(to);
+
+	set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
+}
+
+/**
+ * vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end)
+ *			to the page which @reuse is mapped to, then free vmemmap
+ *			which the range are mapped to.
+ * @start:	start address of the vmemmap virtual address range that we want
+ *		to remap.
+ * @end:	end address of the vmemmap virtual address range that we want to
+ *		remap.
+ * @reuse:	reuse address.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+static int vmemmap_remap_free(unsigned long start, unsigned long end,
+			      unsigned long reuse)
+{
+	int ret;
+	LIST_HEAD(vmemmap_pages);
+	struct vmemmap_remap_walk walk = {
+		.remap_pte	= vmemmap_remap_pte,
+		.reuse_addr	= reuse,
+		.vmemmap_pages	= &vmemmap_pages,
+	};
+
+	/*
+	 * In order to make remapping routine most efficient for the huge pages,
+	 * the routine of vmemmap page table walking has the following rules
+	 * (see more details from the vmemmap_pte_range()):
+	 *
+	 * - The range [@start, @end) and the range [@reuse, @reuse + PAGE_SIZE)
+	 *   should be continuous.
+	 * - The @reuse address is part of the range [@reuse, @end) that we are
+	 *   walking which is passed to vmemmap_remap_range().
+	 * - The @reuse address is the first in the complete range.
+	 *
+	 * So we need to make sure that @start and @reuse meet the above rules.
+	 */
+	BUG_ON(start - reuse != PAGE_SIZE);
+
+	mmap_read_lock(&init_mm);
+	ret = vmemmap_remap_range(reuse, end, &walk);
+	if (ret && walk.nr_walked) {
+		end = reuse + walk.nr_walked * PAGE_SIZE;
+		/*
+		 * vmemmap_pages contains pages from the previous
+		 * vmemmap_remap_range call which failed.  These
+		 * are pages which were removed from the vmemmap.
+		 * They will be restored in the following call.
+		 */
+		walk = (struct vmemmap_remap_walk) {
+			.remap_pte	= vmemmap_restore_pte,
+			.reuse_addr	= reuse,
+			.vmemmap_pages	= &vmemmap_pages,
+		};
+
+		vmemmap_remap_range(reuse, end, &walk);
+	}
+	mmap_read_unlock(&init_mm);
+
+	free_vmemmap_page_list(&vmemmap_pages);
+
+	return ret;
+}
+
+static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
+				   gfp_t gfp_mask, struct list_head *list)
+{
+	unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
+	int nid = page_to_nid((struct page *)start);
+	struct page *page, *next;
+
+	while (nr_pages--) {
+		page = alloc_pages_node(nid, gfp_mask, 0);
+		if (!page)
+			goto out;
+		list_add_tail(&page->lru, list);
+	}
+
+	return 0;
+out:
+	list_for_each_entry_safe(page, next, list, lru)
+		__free_pages(page, 0);
+	return -ENOMEM;
+}
+
+/**
+ * vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end)
+ *			 to the page which is from the @vmemmap_pages
+ *			 respectively.
+ * @start:	start address of the vmemmap virtual address range that we want
+ *		to remap.
+ * @end:	end address of the vmemmap virtual address range that we want to
+ *		remap.
+ * @reuse:	reuse address.
+ * @gfp_mask:	GFP flag for allocating vmemmap pages.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+static int vmemmap_remap_alloc(unsigned long start, unsigned long end,
+			       unsigned long reuse, gfp_t gfp_mask)
+{
+	LIST_HEAD(vmemmap_pages);
+	struct vmemmap_remap_walk walk = {
+		.remap_pte	= vmemmap_restore_pte,
+		.reuse_addr	= reuse,
+		.vmemmap_pages	= &vmemmap_pages,
+	};
+
+	/* See the comment in the vmemmap_remap_free(). */
+	BUG_ON(start - reuse != PAGE_SIZE);
+
+	if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages))
+		return -ENOMEM;
+
+	mmap_read_lock(&init_mm);
+	vmemmap_remap_range(reuse, end, &walk);
+	mmap_read_unlock(&init_mm);
+
+	return 0;
+}
+
 DEFINE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
 EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);