Re: [PATCH] zsmalloc: drop unused member 'mapping_area->huge'

[xuyiping]

HI, Sergery

On 2016/2/17 10:26, Sergey Senozhatsky wrote:
Hello,
On (02/17/16 09:56), YiPing Xu wrote:
  static int create_handle_cache(struct zs_pool *pool)
@@ -1127,11 +1126,9 @@ static void __zs_unmap_object(struct mapping_area *area,
                goto out;

        buf = area->vm_buf;
-       if (!area->huge) {
-               buf = buf + ZS_HANDLE_SIZE;
-               size -= ZS_HANDLE_SIZE;
-               off += ZS_HANDLE_SIZE;
-       }
+       buf = buf + ZS_HANDLE_SIZE;
+       size -= ZS_HANDLE_SIZE;
+       off += ZS_HANDLE_SIZE;

        sizes[0] = PAGE_SIZE - off;
        sizes[1] = size - sizes[0];


hm, indeed.

shouldn't it depend on class->huge?

void *zs_map_object()
{

        if (off + class->size <= PAGE_SIZE) {

for huge object, the code will get into this branch, there is no more 
huge object process in __zs_map_object.

                /* this object is contained entirely within a page */
                area->vm_addr = kmap_atomic(page);
                ret = area->vm_addr + off;
                goto out;
        }


        void *ret = __zs_map_object(area, pages, off, class->size);

        if (!class->huge)
                ret += ZS_HANDLE_SIZE;  /* area->vm_buf + ZS_HANDLE_SIZE */

        return ret;
}

void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
{
        ..

        area = this_cpu_ptr(&zs_map_area);
        if (off + class->size <= PAGE_SIZE)

for huge object, the code will get into this branch, so, in 
__zs_unmap_object there is no depend on class->huge.

it is a little implicated here.

                kunmap_atomic(area->vm_addr);
        else {
                struct page *pages[2];

                pages[0] = page;
                pages[1] = get_next_page(page);
                BUG_ON(!pages[1]);

                __zs_unmap_object(area, pages, off, class->size);
        }

        ..
}


static void __zs_unmap_object(struct mapping_area *area...)
{
        char *buf = area->vm_buf;

        /* handle is in page->private for class->huge */

        buf = buf + ZS_HANDLE_SIZE;
        size -= ZS_HANDLE_SIZE;
        off += ZS_HANDLE_SIZE;

        memcpy(..);
}

        -ss

.