linux-kernel - [PATCHv2 2/2] zsmalloc: simplify read begin/end logic

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Message-ID: <20260107052145.3586917-2-senozhatsky@chromium.org>
Date: Wed,  7 Jan 2026 14:21:45 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Yosry Ahmed <yosry.ahmed@...ux.dev>,
	Nhat Pham <nphamcs@...il.com>
Cc: Minchan Kim <minchan@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Brian Geffon <bgeffon@...gle.com>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCHv2 2/2] zsmalloc: simplify read begin/end logic

From: Yosry Ahmed <yosry.ahmed@...ux.dev>

When we switched from using class->size (for spans detection)
to actual compressed object size, we had to compensate for
the fact that class->size implicitly took inlined handle
into consideration.  In fact, instead of adjusting the size
of compressed object (adding handle offset for non-huge size
classes), we can move some lines around and simplify the
code: there are already paths in read_begin/end that compensate
for inlined object handle offset.

Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
---
 mm/zsmalloc.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 119c196a287a..cc3d9501ae21 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1088,7 +1088,7 @@ void *zs_obj_read_begin(struct zs_pool *pool, unsigned long handle,
 	off = offset_in_page(class->size * obj_idx);
 
 	if (!ZsHugePage(zspage))
-		mem_len += ZS_HANDLE_SIZE;
+		off += ZS_HANDLE_SIZE;
 
 	if (off + mem_len <= PAGE_SIZE) {
 		/* this object is contained entirely within a page */
@@ -1110,9 +1110,6 @@ void *zs_obj_read_begin(struct zs_pool *pool, unsigned long handle,
 				 0, sizes[1]);
 	}
 
-	if (!ZsHugePage(zspage))
-		addr += ZS_HANDLE_SIZE;
-
 	return addr;
 }
 EXPORT_SYMBOL_GPL(zs_obj_read_begin);
@@ -1133,11 +1130,9 @@ void zs_obj_read_end(struct zs_pool *pool, unsigned long handle,
 	off = offset_in_page(class->size * obj_idx);
 
 	if (!ZsHugePage(zspage))
-		mem_len += ZS_HANDLE_SIZE;
+		off += ZS_HANDLE_SIZE;
 
 	if (off + mem_len <= PAGE_SIZE) {
-		if (!ZsHugePage(zspage))
-			off += ZS_HANDLE_SIZE;
 		handle_mem -= off;
 		kunmap_local(handle_mem);
 	}
-- 
2.52.0.351.gbe84eed79e-goog