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Date: Tue, 2 Dec 2014 11:49:44 +0900
From: Minchan Kim <minchan@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Nitin Gupta <ngupta@...are.org>,
Dan Streetman <ddstreet@...e.org>,
Seth Jennings <sjennings@...iantweb.net>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Luigi Semenzato <semenzato@...gle.com>,
Jerome Marchand <jmarchan@...hat.com>, juno.choi@....com,
seungho1.park@....com, Minchan Kim <minchan@...nel.org>
Subject: [RFC 3/6] zsmalloc: implement reverse mapping
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 there.
IOW, *(mapped address by zs_map_object - ZS_HANDLE_SIZE) == handle.
Signed-off-by: Minchan Kim <minchan@...nel.org>
---
mm/zsmalloc.c | 55 +++++++++++++++++++++++++++++++++++--------------------
1 file changed, 35 insertions(+), 20 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 5f3f9119705e..1eec2a539f77 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -213,8 +213,12 @@ 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 {
+ /* Handle of next free chunk (encodes <PFN, obj_idx>) */
+ void *next;
+ /* Handle of object allocated to user */
+ unsigned long handle;
+ };
};
struct zs_pool {
@@ -245,7 +249,9 @@ struct mapping_area {
};
static unsigned long __zs_malloc(struct zs_pool *pool,
- struct size_class *class, gfp_t flags);
+ struct size_class *class, gfp_t flags,
+ unsigned long handle);
+
static void __zs_free(struct zs_pool *pool, struct size_class *class,
unsigned long handle);
@@ -618,7 +624,7 @@ static unsigned long handle_to_obj(struct zs_pool *pool, unsigned long handle)
static unsigned long alloc_handle(struct zs_pool *pool)
{
return __zs_malloc(pool, pool->handle_class,
- pool->flags & ~__GFP_HIGHMEM);
+ pool->flags & ~__GFP_HIGHMEM, 0);
}
static void free_handle(struct zs_pool *pool, unsigned long handle)
@@ -873,18 +879,22 @@ 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;
- sizes[0] = PAGE_SIZE - off;
+ /* We shouldn't overwrite handle */
+ buf = area->vm_buf + ZS_HANDLE_SIZE;
+ size -= ZS_HANDLE_SIZE;
+
+ sizes[0] = PAGE_SIZE - off - ZS_HANDLE_SIZE;
sizes[1] = size - sizes[0];
/* copy per-cpu buffer to object */
addr = kmap_atomic(pages[0]);
- memcpy(addr + off, buf, sizes[0]);
+ memcpy(addr + off + ZS_HANDLE_SIZE, buf, sizes[0]);
kunmap_atomic(addr);
addr = kmap_atomic(pages[1]);
memcpy(addr, buf + sizes[0], sizes[1]);
@@ -1138,7 +1148,7 @@ void zs_destroy_pool(struct zs_pool *pool)
EXPORT_SYMBOL_GPL(zs_destroy_pool);
static unsigned long __zs_malloc(struct zs_pool *pool,
- struct size_class *class, gfp_t flags)
+ struct size_class *class, gfp_t flags, unsigned long handle)
{
unsigned long obj;
struct link_free *link;
@@ -1168,10 +1178,19 @@ static unsigned long __zs_malloc(struct zs_pool *pool,
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));
+ link->handle = handle;
kunmap_atomic(vaddr);
first_page->inuse++;
+
+ if (handle) {
+ unsigned long *h_addr;
+
+ /* associate handle with obj */
+ h_addr = handle_to_addr(pool, handle);
+ *h_addr = obj;
+ }
+
/* Now move the zspage to another fullness group, if required */
fix_fullness_group(class, first_page);
spin_unlock(&class->lock);
@@ -1192,9 +1211,8 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
{
unsigned long obj, handle;
struct size_class *class;
- unsigned long *h_addr;
- if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
+ if (unlikely(!size || (size + ZS_HANDLE_SIZE) > ZS_MAX_ALLOC_SIZE))
return 0;
/* allocate handle */
@@ -1202,18 +1220,15 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
if (!handle)
goto out;
- /* allocate obj */
+ /* allocate obj and associate it with handle */
+ size += ZS_HANDLE_SIZE;
class = pool->size_class[get_size_class_index(size)];
- obj = __zs_malloc(pool, class, pool->flags);
+ obj = __zs_malloc(pool, class, pool->flags, handle);
if (!obj) {
- __zs_free(pool, pool->handle_class, handle);
+ free_handle(pool, handle);
handle = 0;
goto out;
}
-
- /* associate handle with obj */
- h_addr = handle_to_addr(pool, handle);
- *h_addr = obj;
out:
return handle;
}
@@ -1335,7 +1350,7 @@ 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;
+ return area->vm_addr + off + ZS_HANDLE_SIZE;
}
/* this object spans two pages */
@@ -1343,7 +1358,7 @@ 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);
+ return __zs_map_object(area, pages, off, class->size) + ZS_HANDLE_SIZE;
}
EXPORT_SYMBOL_GPL(zs_map_object);
--
2.0.0
--
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