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From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Dan Streetman <ddstreet@ieee.org>,
	Seth Jennings <sjennings@variantweb.net>,
	Nitin Gupta <ngupta@vflare.org>, Juneho Choi <juno.choi@lge.com>,
	Gunho Lee <gunho.lee@lge.com>,
	Luigi Semenzato <semenzato@google.com>,
	Jerome Marchand <jmarchan@redhat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Minchan Kim <minchan@kernel.org>
Subject: [PATCH v1 03/10] zsmalloc: implement reverse mapping
Date: Wed, 21 Jan 2015 15:14:19 +0900	[thread overview]
Message-ID: <1421820866-26521-4-git-send-email-minchan@kernel.org> (raw)
In-Reply-To: <1421820866-26521-1-git-send-email-minchan@kernel.org>

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 <minchan@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


  parent reply	other threads:[~2015-01-21  6:18 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-21  6:14 [PATCH v1 00/10] zsmalloc compaction support Minchan Kim
2015-01-21  6:14 ` [PATCH v1 01/10] zram: avoid calling of zram_meta_free under init_lock Minchan Kim
2015-01-21 14:21   ` Sergey Senozhatsky
2015-01-23  1:03     ` Minchan Kim
2015-01-23  1:15       ` Minchan Kim
2015-01-21  6:14 ` [PATCH v1 02/10] zsmalloc: decouple handle and object Minchan Kim
2015-01-26  2:53   ` Ganesh Mahendran
2015-01-27  3:27     ` Minchan Kim
2015-01-21  6:14 ` Minchan Kim [this message]
2015-01-21  6:14 ` [PATCH v1 04/10] zsmalloc: factor out obj_[malloc|free] Minchan Kim
2015-01-21  6:14 ` [PATCH v1 05/10] zsmalloc: add status bit Minchan Kim
2015-01-21  6:14 ` [PATCH v1 06/10] zsmalloc: support compaction Minchan Kim
2015-01-21  6:14 ` [PATCH v1 07/10] zsmalloc: adjust ZS_ALMOST_FULL Minchan Kim
2015-01-21  6:14 ` [PATCH v1 08/10] zram: support compaction Minchan Kim
2015-01-21  6:14 ` [PATCH v1 09/10] zsmalloc: add fullness into stat Minchan Kim
2015-01-21  6:14 ` [PATCH v1 10/10] zsmalloc: record handle in page->private for huge object Minchan Kim

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