This patch supports reverse mapping which gets handle from object.
For keeping handle per object, it allocates ZS_HANDLE_SIZE greater
than size user requested and stores handle in the extra space.
IOW, *(address mapped by zs_map_object - ZS_HANDLE_SIZE) == handle.
Signed-off-by: Minchan Kim <minc...@kernel.org>
---
mm/zsmalloc.c | 38 ++++++++++++++++++++++++++++++--------
1 file changed, 30 insertions(+), 8 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 9436ee8..2df2f1b 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -142,7 +142,8 @@
/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
#define ZS_MIN_ALLOC_SIZE \
MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
-#define ZS_MAX_ALLOC_SIZE PAGE_SIZE
+/* each chunk includes extra space to keep handle */
+#define ZS_MAX_ALLOC_SIZE (PAGE_SIZE + ZS_HANDLE_SIZE)
/*
* On systems with 4K page size, this gives 255 size classes! There is a
@@ -235,8 +236,17 @@ struct size_class {
* This must be power of 2 and less than or equal to ZS_ALIGN
*/
struct link_free {
- /* Handle of next free chunk (encodes <PFN, obj_idx>) */
- void *next;
+ union {
+ /*
+ * Position of next free chunk (encodes <PFN, obj_idx>)
+ * It's valid for non-allocated object
+ */
+ void *next;
+ /*
+ * Handle of allocated object.
+ */
+ unsigned long handle;
+ };
};
struct zs_pool {
@@ -896,12 +906,16 @@ static void __zs_unmap_object(struct mapping_area *area,
{
int sizes[2];
void *addr;
- char *buf = area->vm_buf;
+ char *buf;
/* no write fastpath */
if (area->vm_mm == ZS_MM_RO)
goto out;
+ buf = area->vm_buf + ZS_HANDLE_SIZE;
+ size -= ZS_HANDLE_SIZE;
+ off += ZS_HANDLE_SIZE;
+
sizes[0] = PAGE_SIZE - off;
sizes[1] = size - sizes[0];
@@ -1196,6 +1210,7 @@ void *zs_map_object(struct zs_pool *pool, unsigned long
handle,
struct size_class *class;
struct mapping_area *area;
struct page *pages[2];
+ void *ret;
BUG_ON(!handle);
@@ -1217,7 +1232,8 @@ void *zs_map_object(struct zs_pool *pool, unsigned long
handle,
if (off + class->size <= PAGE_SIZE) {
/* this object is contained entirely within a page */
area->vm_addr = kmap_atomic(page);
- return area->vm_addr + off;
+ ret = area->vm_addr + off;
+ goto out;
}
/* this object spans two pages */
@@ -1225,7 +1241,9 @@ void *zs_map_object(struct zs_pool *pool, unsigned long
handle,
pages[1] = get_next_page(page);
BUG_ON(!pages[1]);
- return __zs_map_object(area, pages, off, class->size);
+ ret = __zs_map_object(area, pages, off, class->size);
+out:
+ return ret + ZS_HANDLE_SIZE;
}
EXPORT_SYMBOL_GPL(zs_map_object);
@@ -1282,13 +1300,15 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t
size)
struct page *first_page, *m_page;
unsigned long m_objidx, m_offset;
- if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
+ if (unlikely(!size || (size + ZS_HANDLE_SIZE) > ZS_MAX_ALLOC_SIZE))
return 0;
handle = alloc_handle(pool);
if (!handle)
return 0;
+ /* extra space in chunk to keep the handle */
+ size += ZS_HANDLE_SIZE;
class = pool->size_class[get_size_class_index(size)];
spin_lock(&class->lock);
@@ -1318,7 +1338,9 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
vaddr = kmap_atomic(m_page);
link = (struct link_free *)vaddr + m_offset / sizeof(*link);
first_page->freelist = link->next;
- memset(link, POISON_INUSE, sizeof(*link));
+
+ /* record handle in the header of allocated chunk */
+ link->handle = handle;
kunmap_atomic(vaddr);
first_page->inuse++;
--
1.9.3
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
