linux-kernel - Re: [PATCH] zsmalloc: use actual object size to detect spans

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Message-ID: <p3xtt4xygqo235c6yuecneot66isu3nvwbnh3oqz4smvzv6wvb@vgvauzche5bn>
Date: Wed, 7 Jan 2026 16:12:44 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Nhat Pham <nphamcs@...il.com>, Minchan Kim <minchan@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>, Brian Geffon <bgeffon@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH] zsmalloc: use actual object size to detect spans

A correction:

On (26/01/07 14:30), Sergey Senozhatsky wrote:
> > We increase the offset by 8 bytes (ZS_HANDLE_SIZE), but we still copy 48
> > bytes, even though 48 bytes includes both the object and ZS_HANDLE_SIZE.
> > So we end up copying 8 bytes beyond the end of the object, which puts us
> > in the next page which we should not be copying.
> 
> Correct.  We increased it twice: off +8 and mem_len +8.
                                              ^^ class->size (implicit +8)

I tested your patch as is, w/o applying mine.