[PATCH 06/10] drm/i915: use vmap in shmem_pin_map

[Christoph Hellwig <hch@xxxxxx>]

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).  Switch to use vmap, and use vfree to free both the
vmalloc mapping and the page array, as well as dropping the references
to each page.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/shmem_utils.c | 76 +++++++--------------------
 1 file changed, 18 insertions(+), 58 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c 
b/drivers/gpu/drm/i915/gt/shmem_utils.c
index 43c7acbdc79dea..f011ea42487e11 100644
--- a/drivers/gpu/drm/i915/gt/shmem_utils.c
+++ b/drivers/gpu/drm/i915/gt/shmem_utils.c
@@ -49,80 +49,40 @@ struct file *shmem_create_from_object(struct 
drm_i915_gem_object *obj)
        return file;
 }
 
-static size_t shmem_npte(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)
-                       return NULL;
-       }
+       struct page **pages;
+       size_t n_pages, i;
+       void *vaddr;
 
-       area = alloc_vm_area(n_pte << PAGE_SHIFT, mem);
-       if (!area) {
-               if (mem != stack)
-                       kvfree(mem);
+       n_pages = file->f_mapping->host->i_size >> PAGE_SHIFT;
+       pages = kvmalloc_array(n_pages, sizeof(*pages), GFP_KERNEL);
+       if (!pages)
                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, VM_MAP_PUT_PAGES, PAGE_KERNEL);
+       if (!vaddr)
+               goto err_page;
        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]);
+       kvfree(pages);
        return NULL;
 }
 
 void shmem_unpin_map(struct file *file, void *ptr)
 {
        mapping_clear_unevictable(file->f_mapping);
-       __shmem_unpin_map(file, ptr, shmem_npte(file));
+       vfree(ptr);
 }
 
 static int __shmem_rw(struct file *file, loff_t off,
-- 
2.28.0