Re: [PATCH 2/9] mm: Provide new get_vaddr_frames() helper

[Jan Kara <jack@suse.cz>]

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On Thu 28-05-15 16:24:02, Andrew Morton wrote:
> On Wed, 13 May 2015 15:08:08 +0200 Jan Kara <jack@suse.cz> wrote:
> 
> > Provide new function get_vaddr_frames().  This function maps virtual
> > addresses from given start and fills given array with page frame numbers of
> > the corresponding pages. If given 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. Caller
> > must make sure pfns aren't reused for anything else while he is using
> > them.
> > 
> > This function is created for various drivers to simplify handling of
> > their buffers.
> > 
> > Acked-by: Mel Gorman <mgorman@suse.de>
> > Acked-by: Vlastimil Babka <vbabka@suse.cz>
> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> >  include/linux/mm.h |  44 +++++++++++
> >  mm/gup.c           | 226 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 
> That's a lump of new code which many kernels won't be needing.  Can we
> put all this in a new .c file and select it within drivers/media
> Kconfig?
  So the attached patch should do what you had in mind. OK?

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR

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>From d18fc7863fc62d8ad0c1747b789a0dcf032ccf42 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Tue, 2 Jun 2015 16:40:32 +0200
Subject: [PATCH] mm: Move get_vaddr_frames() behind a config option

get_vaddr_frames() is used by relatively rare drivers so hide it and the
related functions behind a config option that is selected only by
drivers that need the infrastructure.

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 drivers/gpu/drm/exynos/Kconfig      |   1 +
 drivers/media/platform/omap/Kconfig |   1 +
 drivers/media/v4l2-core/Kconfig     |   1 +
 mm/Kconfig                          |   3 +
 mm/Makefile                         |   1 +
 mm/frame-vec.c                      | 233 ++++++++++++++++++++++++++++++++++++
 mm/gup.c                            | 225 ----------------------------------
 7 files changed, 240 insertions(+), 225 deletions(-)
 create mode 100644 mm/frame-vec.c

diff --git a/drivers/gpu/drm/exynos/Kconfig b/drivers/gpu/drm/exynos/Kconfig
index 0a6780367d28..b2fac87137c7 100644
--- a/drivers/gpu/drm/exynos/Kconfig
+++ b/drivers/gpu/drm/exynos/Kconfig
@@ -71,6 +71,7 @@ config DRM_EXYNOS_VIDI
 config DRM_EXYNOS_G2D
 	bool "Exynos DRM G2D"
 	depends on DRM_EXYNOS && !VIDEO_SAMSUNG_S5P_G2D
+	select FRAME_VEC
 	help
 	  Choose this option if you want to use Exynos G2D for DRM.
 
diff --git a/drivers/media/platform/omap/Kconfig b/drivers/media/platform/omap/Kconfig
index dc2aaab54aef..7cceca7b184d 100644
--- a/drivers/media/platform/omap/Kconfig
+++ b/drivers/media/platform/omap/Kconfig
@@ -10,6 +10,7 @@ config VIDEO_OMAP2_VOUT
 	select OMAP2_DSS if HAS_IOMEM && ARCH_OMAP2PLUS
 	select OMAP2_VRFB if ARCH_OMAP2 || ARCH_OMAP3
 	select VIDEO_OMAP2_VOUT_VRFB if VIDEO_OMAP2_VOUT && OMAP2_VRFB
+	select FRAME_VEC
 	default n
 	---help---
 	  V4L2 Display driver support for OMAP2/3 based boards.
diff --git a/drivers/media/v4l2-core/Kconfig b/drivers/media/v4l2-core/Kconfig
index ba7e21a73023..957e5a18b0ff 100644
--- a/drivers/media/v4l2-core/Kconfig
+++ b/drivers/media/v4l2-core/Kconfig
@@ -73,6 +73,7 @@ config VIDEOBUF2_CORE
 
 config VIDEOBUF2_MEMOPS
 	tristate
+	select FRAME_VEC
 
 config VIDEOBUF2_DMA_CONTIG
 	tristate
diff --git a/mm/Kconfig b/mm/Kconfig
index 390214da4546..d039615e8f82 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -635,3 +635,6 @@ config MAX_STACK_SIZE_MB
 	  changed to a smaller value in which case that is used.
 
 	  A sane initial value is 80 MB.
+
+config FRAME_VEC
+	bool
diff --git a/mm/Makefile b/mm/Makefile
index 98c4eaeabdcb..d38305462e17 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_VEC)	+= frame-vec.o
diff --git a/mm/frame-vec.c b/mm/frame-vec.c
new file mode 100644
index 000000000000..5d85bcd150ae
--- /dev/null
+++ b/mm/frame-vec.c
@@ -0,0 +1,233 @@
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/mm.h>
+#include <linux/slab.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);
+	if (!is_vmalloc_addr(vec))
+		kfree(vec);
+	else
+		vfree(vec);
+}
+EXPORT_SYMBOL(frame_vector_destroy);
+
diff --git a/mm/gup.c b/mm/gup.c
index 9d7f4fde30cb..222d57e335f9 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -937,231 +937,6 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
 	return ret;	/* 0 or negative error code */
 }
 
-/*
- * 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);
-	if (!is_vmalloc_addr(vec))
-		kfree(vec);
-	else
-		vfree(vec);
-}
-EXPORT_SYMBOL(frame_vector_destroy);
-
 /**
  * get_dump_page() - pin user page in memory while writing it to core dump
  * @addr: user address
-- 
2.1.4