[merged mm-stable] mm-zsmalloc-dont-need-to-reserve-lsb-in-handle.patch removed from -mm tree

[merged mm-stable] mm-zsmalloc-dont-need-to-reserve-lsb-in-handle.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/zsmalloc: don't need to reserve LSB in handle
has been removed from the -mm tree.  Its filename was
     mm-zsmalloc-dont-need-to-reserve-lsb-in-handle.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Chengming Zhou <chengming.zhou@linux.dev>
Subject: mm/zsmalloc: don't need to reserve LSB in handle
Date: Wed, 28 Feb 2024 02:38:54 +0000

We will save allocated tag in the object header to indicate that it's
allocated.

	handle |= OBJ_ALLOCATED_TAG;

So the object header needs to reserve LSB for this tag bit.

But the handle itself doesn't need to reserve LSB to save tag, since it's
only used to find the position of object, by (pfn + obj_idx).  So remove
LSB reserve from handle, one more bit can be used as obj_idx.

Link: https://lkml.kernel.org/r/20240228023854.3511239-1-chengming.zhou@linux.dev
Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/zsmalloc.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

--- a/mm/zsmalloc.c~mm-zsmalloc-dont-need-to-reserve-lsb-in-handle
+++ a/mm/zsmalloc.c
@@ -110,7 +110,7 @@
 #define OBJ_TAG_BITS	1
 #define OBJ_TAG_MASK	OBJ_ALLOCATED_TAG
 
-#define OBJ_INDEX_BITS	(BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
+#define OBJ_INDEX_BITS	(BITS_PER_LONG - _PFN_BITS)
 #define OBJ_INDEX_MASK	((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
 
 #define HUGE_BITS	1
@@ -737,14 +737,12 @@ static struct page *get_next_page(struct
 static void obj_to_location(unsigned long obj, struct page **page,
 				unsigned int *obj_idx)
 {
-	obj >>= OBJ_TAG_BITS;
 	*page = pfn_to_page(obj >> OBJ_INDEX_BITS);
 	*obj_idx = (obj & OBJ_INDEX_MASK);
 }
 
 static void obj_to_page(unsigned long obj, struct page **page)
 {
-	obj >>= OBJ_TAG_BITS;
 	*page = pfn_to_page(obj >> OBJ_INDEX_BITS);
 }
 
@@ -759,7 +757,6 @@ static unsigned long location_to_obj(str
 
 	obj = page_to_pfn(page) << OBJ_INDEX_BITS;
 	obj |= obj_idx & OBJ_INDEX_MASK;
-	obj <<= OBJ_TAG_BITS;
 
 	return obj;
 }
_

Patches currently in -mm which might be from chengming.zhou@linux.dev are