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Date:   Tue, 20 Aug 2019 11:53:07 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To:     Henry Burns <henryburns@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Minchan Kim <minchan@kernel.org>, Nitin Gupta <ngupta@vflare.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Shakeel Butt <shakeelb@google.com>,
        Jonathan Adams <jwadams@google.com>,
        HenryBurns <henrywolfeburns@gmail.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2 v2] mm/zsmalloc.c: Migration can leave pages in
 ZS_EMPTY indefinitely
Message-ID: <20190820025307.GC500@jagdpanzerIV>
References: <20190809181751.219326-1-henryburns@google.com>
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On (08/09/19 11:17), Henry Burns wrote:
> In zs_page_migrate() we call putback_zspage() after we have finished
> migrating all pages in this zspage. However, the return value is ignored.
> If a zs_free() races in between zs_page_isolate() and zs_page_migrate(),
> freeing the last object in the zspage, putback_zspage() will leave the page
> in ZS_EMPTY for potentially an unbounded amount of time.
> 
> To fix this, we need to do the same thing as zs_page_putback() does:
> schedule free_work to occur.  To avoid duplicated code, move the
> sequence to a new putback_zspage_deferred() function which both
> zs_page_migrate() and zs_page_putback() call.
> 
> Fixes: 48b4800a1c6a ("zsmalloc: page migration support")
> Signed-off-by: Henry Burns <henryburns@google.com>

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

+ Andrew

	-ss