4 files changed, 235 insertions, 0 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 6413d027c0b2..0d9fdcd01e47 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -677,3 +677,6 @@ config ZONE_DEVICE
           mapping in an O_DIRECT operation, among other things.
 
           If FS_DAX is enabled, then say Y.
+
+config FRAME_VECTOR
+        bool
diff --git a/mm/Makefile b/mm/Makefile
index 56f8eed73f1a..2ed43191fc3b 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -80,3 +80,4 @@ obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
 obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
 obj-$(CONFIG_USERFAULTFD) += userfaultfd.o
 obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o
+obj-$(CONFIG_FRAME_VECTOR) += frame_vector.o
diff --git a/mm/early_ioremap.c b/mm/early_ioremap.c
index 23f744d77ce0..17ae14b5aefa 100644
--- a/mm/early_ioremap.c
+++ b/mm/early_ioremap.c
@@ -15,6 +15,7 @@
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <asm/fixmap.h>
+#include <asm/early_ioremap.h>
 
 #ifdef CONFIG_MMU
 static int early_ioremap_debug __initdata;
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);