linux-kernel - Re: [PATCH RESEND 2/3] mm/zsmalloc: remove migrate_write_lock

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Message-ID: <20240223055626.GV11472@google.com>
Date: Fri, 23 Feb 2024 14:56:26 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Chengming Zhou <chengming.zhou@...ux.dev>
Cc: hannes@...xchg.org, Sergey Senozhatsky <senozhatsky@...omium.org>,
	Minchan Kim <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, nphamcs@...il.com,
	yosryahmed@...gle.com, linux-mm@...ck.org,
	Chengming Zhou <zhouchengming@...edance.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 2/3] mm/zsmalloc: remove
 migrate_write_lock_nested()

On (24/02/20 11:36), Chengming Zhou wrote:
> From: Chengming Zhou <zhouchengming@...edance.com>
> 
> The migrate write lock is to protect the race between zspage migration
> and zspage objects' map users.
> 
> We only need to lock out the map users of src zspage, not dst zspage,
> which is safe to map by users concurrently, since we only need to do
> obj_malloc() from dst zspage.
> 
> So we can remove the migrate_write_lock_nested() use case.
> 
> As we are here, cleanup the __zs_compact() by moving putback_zspage()
> outside of migrate_write_unlock since we hold pool lock, no malloc or
> free users can come in.
> 
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>

Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>