3 files changed, 234 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig
index e79de2bd12cd..7f146dd32fc5 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -654,3 +654,6 @@ config DEFERRED_STRUCT_PAGE_INIT
 	  when kswapd starts. This has a potential performance impact on
 	  processes running early in the lifetime of the systemm until kswapd
 	  finishes the initialisation.
+
+config FRAME_VECTOR
+	bool
diff --git a/mm/Makefile b/mm/Makefile
index 98c4eaeabdcb..be5d5c866305 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -78,3 +78,4 @@ obj-$(CONFIG_CMA)	+= cma.o
 obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o
 obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
 obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
+obj-$(CONFIG_FRAME_VECTOR) += frame_vector.o
diff --git a/mm/frame_vector.c b/mm/frame_vector.c
new file mode 100644
index 000000000000..cdabcb93c6a6
--- /dev/null
+++ b/mm/frame_vector.c
@@ -0,0 +1,230 @@
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/pagemap.h>
+#include <linux/sched.h>
+
+/*
+ * get_vaddr_frames() - map virtual addresses to pfns
+ * @start:	starting user address
+ * @nr_frames:	number of pages / pfns from start to map
+ * @write:	whether pages will be written to by the caller
+ * @force:	whether to force write access even if user mapping is
+ *		readonly. See description of the same argument of
+		get_user_pages().
+ * @vec:	structure which receives pages / pfns of the addresses mapped.
+ *		It should have space for at least nr_frames entries.
+ *
+ * This function maps virtual addresses from @start and fills @vec structure
+ * with page frame numbers or page pointers to corresponding pages (choice
+ * depends on the type of the vma underlying the virtual address). If @start
+ * belongs to a normal vma, the function grabs reference to each of the pages
+ * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
+ * touch page structures and the caller must make sure pfns aren't reused for
+ * anything else while he is using them.
+ *
+ * The function returns number of pages mapped which may be less than
+ * @nr_frames. In particular we stop mapping if there are more vmas of
+ * different type underlying the specified range of virtual addresses.
+ * When the function isn't able to map a single page, it returns error.
+ *
+ * This function takes care of grabbing mmap_sem as necessary.
+ */
+int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
+		     bool write, bool force, struct frame_vector *vec)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	int ret = 0;
+	int err;
+	int locked;
+
+	if (nr_frames == 0)
+		return 0;
+
+	if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
+		nr_frames = vec->nr_allocated;
+
+	down_read(&mm->mmap_sem);
+	locked = 1;
+	vma = find_vma_intersection(mm, start, start + 1);
+	if (!vma) {
+		ret = -EFAULT;
+		goto out;
+	}
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
+		vec->got_ref = true;
+		vec->is_pfns = false;
+		ret = get_user_pages_locked(current, mm, start, nr_frames,
+			write, force, (struct page **)(vec->ptrs), &locked);
+		goto out;
+	}
+
+	vec->got_ref = false;
+	vec->is_pfns = true;
+	do {
+		unsigned long *nums = frame_vector_pfns(vec);
+
+		while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
+			err = follow_pfn(vma, start, &nums[ret]);
+			if (err) {
+				if (ret == 0)
+					ret = err;
+				goto out;
+			}
+			start += PAGE_SIZE;
+			ret++;
+		}
+		/*
+		 * We stop if we have enough pages or if VMA doesn't completely
+		 * cover the tail page.
+		 */
+		if (ret >= nr_frames || start < vma->vm_end)
+			break;
+		vma = find_vma_intersection(mm, start, start + 1);
+	} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
+out:
+	if (locked)
+		up_read(&mm->mmap_sem);
+	if (!ret)
+		ret = -EFAULT;
+	if (ret > 0)
+		vec->nr_frames = ret;
+	return ret;
+}
+EXPORT_SYMBOL(get_vaddr_frames);
+
+/**
+ * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
+ *			them
+ * @vec:	frame vector to put
+ *
+ * Drop references to pages if get_vaddr_frames() acquired them. We also
+ * invalidate the frame vector so that it is prepared for the next call into
+ * get_vaddr_frames().
+ */
+void put_vaddr_frames(struct frame_vector *vec)
+{
+	int i;
+	struct page **pages;
+
+	if (!vec->got_ref)
+		goto out;
+	pages = frame_vector_pages(vec);
+	/*
+	 * frame_vector_pages() might needed to do a conversion when
+	 * get_vaddr_frames() got pages but vec was later converted to pfns.
+	 * But it shouldn't really fail to convert pfns back...
+	 */
+	if (WARN_ON(IS_ERR(pages)))
+		goto out;
+	for (i = 0; i < vec->nr_frames; i++)
+		put_page(pages[i]);
+	vec->got_ref = false;
+out:
+	vec->nr_frames = 0;
+}
+EXPORT_SYMBOL(put_vaddr_frames);
+
+/**
+ * frame_vector_to_pages - convert frame vector to contain page pointers
+ * @vec:	frame vector to convert
+ *
+ * Convert @vec to contain array of page pointers.  If the conversion is
+ * successful, return 0. Otherwise return an error. Note that we do not grab
+ * page references for the page structures.
+ */
+int frame_vector_to_pages(struct frame_vector *vec)
+{
+	int i;
+	unsigned long *nums;
+	struct page **pages;
+
+	if (!vec->is_pfns)
+		return 0;
+	nums = frame_vector_pfns(vec);
+	for (i = 0; i < vec->nr_frames; i++)
+		if (!pfn_valid(nums[i]))
+			return -EINVAL;
+	pages = (struct page **)nums;
+	for (i = 0; i < vec->nr_frames; i++)
+		pages[i] = pfn_to_page(nums[i]);
+	vec->is_pfns = false;
+	return 0;
+}
+EXPORT_SYMBOL(frame_vector_to_pages);
+
+/**
+ * frame_vector_to_pfns - convert frame vector to contain pfns
+ * @vec:	frame vector to convert
+ *
+ * Convert @vec to contain array of pfns.
+ */
+void frame_vector_to_pfns(struct frame_vector *vec)
+{
+	int i;
+	unsigned long *nums;
+	struct page **pages;
+
+	if (vec->is_pfns)
+		return;
+	pages = (struct page **)(vec->ptrs);
+	nums = (unsigned long *)pages;
+	for (i = 0; i < vec->nr_frames; i++)
+		nums[i] = page_to_pfn(pages[i]);
+	vec->is_pfns = true;
+}
+EXPORT_SYMBOL(frame_vector_to_pfns);
+
+/**
+ * frame_vector_create() - allocate & initialize structure for pinned pfns
+ * @nr_frames:	number of pfns slots we should reserve
+ *
+ * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
+ * pfns.
+ */
+struct frame_vector *frame_vector_create(unsigned int nr_frames)
+{
+	struct frame_vector *vec;
+	int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
+
+	if (WARN_ON_ONCE(nr_frames == 0))
+		return NULL;
+	/*
+	 * This is absurdly high. It's here just to avoid strange effects when
+	 * arithmetics overflows.
+	 */
+	if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
+		return NULL;
+	/*
+	 * Avoid higher order allocations, use vmalloc instead. It should
+	 * be rare anyway.
+	 */
+	if (size <= PAGE_SIZE)
+		vec = kmalloc(size, GFP_KERNEL);
+	else
+		vec = vmalloc(size);
+	if (!vec)
+		return NULL;
+	vec->nr_allocated = nr_frames;
+	vec->nr_frames = 0;
+	return vec;
+}
+EXPORT_SYMBOL(frame_vector_create);
+
+/**
+ * frame_vector_destroy() - free memory allocated to carry frame vector
+ * @vec:	Frame vector to free
+ *
+ * Free structure allocated by frame_vector_create() to carry frames.
+ */
+void frame_vector_destroy(struct frame_vector *vec)
+{
+	/* Make sure put_vaddr_frames() got called properly... */
+	VM_BUG_ON(vec->nr_frames > 0);
+	kvfree(vec);
+}
+EXPORT_SYMBOL(frame_vector_destroy);