+ drm-i915-use-vmap-in-shmem_pin_map.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: drm/i915: use vmap in shmem_pin_map
has been added to the -mm tree.  Its filename is
     drm-i915-use-vmap-in-shmem_pin_map.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/drm-i915-use-vmap-in-shmem_pin_map.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/drm-i915-use-vmap-in-shmem_pin_map.patch

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------------------------------------------------------
From: Christoph Hellwig <hch@lst.de>
Subject: drm/i915: use vmap in shmem_pin_map

shmem_pin_map somewhat awkwardly reimplements vmap using alloc_vm_area and
manual pte setup.  The only practical difference is that alloc_vm_area
prefeaults the vmalloc area PTEs, which doesn't seem to be required here
(and could be added to vmap using a flag if actually required).

Link: https://lkml.kernel.org/r/20200918163724.2511-4-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/gpu/drm/i915/gt/shmem_utils.c |   90 ++++++++++--------------
 1 file changed, 38 insertions(+), 52 deletions(-)

--- a/drivers/gpu/drm/i915/gt/shmem_utils.c~drm-i915-use-vmap-in-shmem_pin_map
+++ a/drivers/gpu/drm/i915/gt/shmem_utils.c
@@ -49,80 +49,66 @@ struct file *shmem_create_from_object(st
 	return file;
 }
 
-static size_t shmem_npte(struct file *file)
+static size_t shmem_npages(struct file *file)
 {
 	return file->f_mapping->host->i_size >> PAGE_SHIFT;
 }
 
-static void __shmem_unpin_map(struct file *file, void *ptr, size_t n_pte)
-{
-	unsigned long pfn;
-
-	vunmap(ptr);
-
-	for (pfn = 0; pfn < n_pte; pfn++) {
-		struct page *page;
-
-		page = shmem_read_mapping_page_gfp(file->f_mapping, pfn,
-						   GFP_KERNEL);
-		if (!WARN_ON(IS_ERR(page))) {
-			put_page(page);
-			put_page(page);
-		}
-	}
-}
-
 void *shmem_pin_map(struct file *file)
 {
-	const size_t n_pte = shmem_npte(file);
-	pte_t *stack[32], **ptes, **mem;
-	struct vm_struct *area;
-	unsigned long pfn;
-
-	mem = stack;
-	if (n_pte > ARRAY_SIZE(stack)) {
-		mem = kvmalloc_array(n_pte, sizeof(*mem), GFP_KERNEL);
-		if (!mem)
+	const size_t n_pages = shmem_npages(file);
+	struct page **pages, *stack[32];
+	void *vaddr;
+	long i;
+
+	pages = stack;
+	if (n_pages > ARRAY_SIZE(stack)) {
+		pages = kvmalloc_array(n_pages, sizeof(*pages), GFP_KERNEL);
+		if (!pages)
 			return NULL;
 	}
 
-	area = alloc_vm_area(n_pte << PAGE_SHIFT, mem);
-	if (!area) {
-		if (mem != stack)
-			kvfree(mem);
-		return NULL;
-	}
-
-	ptes = mem;
-	for (pfn = 0; pfn < n_pte; pfn++) {
-		struct page *page;
-
-		page = shmem_read_mapping_page_gfp(file->f_mapping, pfn,
-						   GFP_KERNEL);
-		if (IS_ERR(page))
+	for (i = 0; i < n_pages; i++) {
+		pages[i] = shmem_read_mapping_page_gfp(file->f_mapping, i,
+						       GFP_KERNEL);
+		if (IS_ERR(pages[i]))
 			goto err_page;
-
-		**ptes++ = mk_pte(page,  PAGE_KERNEL);
 	}
 
-	if (mem != stack)
-		kvfree(mem);
+	vaddr = vmap(pages, n_pages, 0, PAGE_KERNEL);
+	if (!vaddr)
+		goto err_page;
 
+	if (pages != stack)
+		kvfree(pages);
 	mapping_set_unevictable(file->f_mapping);
-	return area->addr;
+	return vaddr;
 
 err_page:
-	if (mem != stack)
-		kvfree(mem);
-
-	__shmem_unpin_map(file, area->addr, pfn);
+	while (--i >= 0)
+		put_page(pages[i]);
+	if (pages != stack)
+		kvfree(pages);
 	return NULL;
 }
 
 void shmem_unpin_map(struct file *file, void *ptr)
 {
+	long i = shmem_npages(file);
+
 	mapping_clear_unevictable(file->f_mapping);
-	__shmem_unpin_map(file, ptr, shmem_npte(file));
+	vunmap(ptr);
+
+	for (i = 0; i < shmem_npages(file); i++) {
+		struct page *page;
+
+		page = shmem_read_mapping_page_gfp(file->f_mapping, i,
+						   GFP_KERNEL);
+		if (!WARN_ON(IS_ERR(page))) {
+			put_page(page);
+			put_page(page);
+		}
+	}
 }
 
 static int __shmem_rw(struct file *file, loff_t off,
_

Patches currently in -mm which might be from hch@lst.de are

zsmalloc-switch-from-alloc_vm_area-to-get_vm_area.patch
mm-add-a-vmap_pfn-function.patch
drm-i915-use-vmap-in-shmem_pin_map.patch
drm-i915-use-vmap-in-i915_gem_object_map.patch
xen-xenbus-use-apply_to_page_range-directly-in-xenbus_map_ring_pv.patch
x86-xen-open-code-alloc_vm_area-in-arch_gnttab_valloc.patch