linux-kernel - Re: [PATCH] mm/zsmalloc: don't need to save tag bit in handle

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240227075209.GA11972@google.com>
Date: Tue, 27 Feb 2024 16:52:09 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: chengming.zhou@...ux.dev
Cc: minchan@...nel.org, senozhatsky@...omium.org, akpm@...ux-foundation.org,
	hannes@...xchg.org, nphamcs@...il.com, yosryahmed@...gle.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Chengming Zhou <zhouchengming@...edance.com>
Subject: Re: [PATCH] mm/zsmalloc: don't need to save tag bit in handle

On (24/02/27 03:00), chengming.zhou@...ux.dev wrote:
> 
> We only need to save the position (pfn + obj_idx) in the handle, don't
> need to save tag bit in handle. So one more bit can be used as obj_idx.

[..]

> mm/zsmalloc: don't need to save tag bit in handle

Does this mean "don't need to reserve LSB for tag"?
We still save allocated tag in the handle, that's what

	handle |= OBJ_ALLOCATED_TAG;

does.

> Actually, the tag bit is only useful in zspage's memory space, to tell
> if an object is allocated or not.

I'm not completely sure if I follow this sentence.