[PATCH v2 1/9] mm: Introduce new vm_insert_range API

[Souptick Joarder]

Previouly drivers have their own way of mapping range of
kernel pages/memory into user vma and this was done by
invoking vm_insert_page() within a loop.

As this pattern is common across different drivers, it can
be generalized by creating a new function and use it across
the drivers.

vm_insert_range is the new API which will be used to map a
range of kernel memory/pages to user vma.

This API is tested by Heiko for Rockchip drm driver, on rk3188,
rk3288, rk3328 and rk3399 with graphics.

Signed-off-by: Souptick Joarder <jrdr.linux at gmail.com>
Reviewed-by: Matthew Wilcox <willy at infradead.org>
Tested-by: Heiko Stuebner <heiko at sntech.de>
---
 include/linux/mm_types.h |  3 +++
 mm/memory.c              | 38 ++++++++++++++++++++++++++++++++++++++
 mm/nommu.c               |  7 +++++++
 3 files changed, 48 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5ed8f62..15ae24f 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -523,6 +523,9 @@ extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
 extern void tlb_finish_mmu(struct mmu_gather *tlb,
 				unsigned long start, unsigned long end);
 
+int vm_insert_range(struct vm_area_struct *vma, unsigned long addr,
+			struct page **pages, unsigned long page_count);
+
 static inline void init_tlb_flush_pending(struct mm_struct *mm)
 {
 	atomic_set(&mm->tlb_flush_pending, 0);
diff --git a/mm/memory.c b/mm/memory.c
index 15c417e..84ea46c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1478,6 +1478,44 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
 }
 
 /**
+ * vm_insert_range - insert range of kernel pages into user vma
+ * @vma: user vma to map to
+ * @addr: target user address of this page
+ * @pages: pointer to array of source kernel pages
+ * @page_count: number of pages need to insert into user vma
+ *
+ * This allows drivers to insert range of kernel pages they've allocated
+ * into a user vma. This is a generic function which drivers can use
+ * rather than using their own way of mapping range of kernel pages into
+ * user vma.
+ *
+ * If we fail to insert any page into the vma, the function will return
+ * immediately leaving any previously-inserted pages present.  Callers
+ * from the mmap handler may immediately return the error as their caller
+ * will destroy the vma, removing any successfully-inserted pages. Other
+ * callers should make their own arrangements for calling unmap_region().
+ *
+ * Context: Process context. Called by mmap handlers.
+ * Return: 0 on success and error code otherwise
+ */
+int vm_insert_range(struct vm_area_struct *vma, unsigned long addr,
+			struct page **pages, unsigned long page_count)
+{
+	unsigned long uaddr = addr;
+	int ret = 0, i;
+
+	for (i = 0; i < page_count; i++) {
+		ret = vm_insert_page(vma, uaddr, pages[i]);
+		if (ret < 0)
+			return ret;
+		uaddr += PAGE_SIZE;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(vm_insert_range);
+
+/**
  * vm_insert_page - insert single page into user vma
  * @vma: user vma to map to
  * @addr: target user address of this page
diff --git a/mm/nommu.c b/mm/nommu.c
index 749276b..d6ef5c7 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -473,6 +473,13 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
 }
 EXPORT_SYMBOL(vm_insert_page);
 
+int vm_insert_range(struct vm_area_struct *vma, unsigned long addr,
+			struct page **pages, unsigned long page_count)
+{
+	return -EINVAL;
+}
+EXPORT_SYMBOL(vm_insert_range);
+
 /*
  *  sys_brk() for the most part doesn't need the global kernel
  *  lock, except when an application is doing something nasty
-- 
1.9.1