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Date: Sat, 16 Jan 2016 13:09:13 +0900
From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>, Junil Lee <junil0814.lee@lge.com>,
        ngupta@vflare.org, sergey.senozhatsky.work@gmail.com,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, sergey.senozhatsky@gmail.com
Subject: Re: [PATCH v2] zsmalloc: fix migrate_zspage-zs_free race condition
Message-ID: <20160116040913.GA566@swordfish>
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On (01/15/16 16:49), Vlastimil Babka wrote:
[..]
> 
> Could you please also help making the changelog more clear?
> 
> >
> >>+		free_obj |= BIT(HANDLE_PIN_BIT);
> >>  		record_obj(handle, free_obj);
> 
> I think record_obj() should use WRITE_ONCE() or something like that.
> Otherwise the compiler is IMHO allowed to reorder this, i.e. first to assign
> free_obj to handle, and then add the PIN bit there.

good note.

... or do both things in record_obj() (per Minchan)

	record_obj(handle, obj)
	{
	        *(unsigned long)handle = obj & ~(1<<HANDLE_PIN_BIT);
	}

	-ss