From: Minchan Kim <minchan@kernel.org>
To: Henry Burns <henryburns@google.com>
Cc: Nitin Gupta <ngupta@vflare.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Shakeel Butt <shakeelb@google.com>,
Jonathan Adams <jwadams@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm/zsmalloc.c: Migration can leave pages in ZS_EMPTY indefinitely
Date: Mon, 5 Aug 2019 13:14:40 +0900 [thread overview]
Message-ID: <20190805041440.GA178551@google.com> (raw)
In-Reply-To: <20190802015332.229322-1-henryburns@google.com>
On Thu, Aug 01, 2019 at 06:53:31PM -0700, 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.
Nice catch.
>
> 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.
>
> Signed-off-by: Henry Burns <henryburns@google.com>
Cc: <stable@vger.kernel.org> [4.8+]
Acked-by: Minchan Kim <minchan@kernel.org>
Below a just trivial:
> ---
> mm/zsmalloc.c | 30 ++++++++++++++++++++----------
> 1 file changed, 20 insertions(+), 10 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 1cda3fe0c2d9..efa660a87787 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -1901,6 +1901,22 @@ static void dec_zspage_isolation(struct zspage *zspage)
> zspage->isolated--;
> }
>
> +static void putback_zspage_deferred(struct zs_pool *pool,
> + struct size_class *class,
> + struct zspage *zspage)
> +{
> + enum fullness_group fg;
> +
> + fg = putback_zspage(class, zspage);
> + /*
> + * Due to page_lock, we cannot free zspage immediately
> + * so let's defer.
> + */
Could you move this comment function's description since it becomes
a function?
Thanks.
prev parent reply other threads:[~2019-08-05 4:14 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-02 1:53 [PATCH 1/2] mm/zsmalloc.c: Migration can leave pages in ZS_EMPTY indefinitely Henry Burns
2019-08-02 1:53 ` [PATCH 2/2] mm/zsmalloc.c: Fix race condition in zs_destroy_pool Henry Burns
2019-08-05 4:28 ` Minchan Kim
2019-08-05 17:34 ` Henry Burns
2019-08-06 1:38 ` Minchan Kim
2019-08-06 19:53 ` Henry Burns
2019-08-02 14:58 ` [PATCH 1/2] mm/zsmalloc.c: Migration can leave pages in ZS_EMPTY indefinitely Shakeel Butt
2019-08-02 15:09 ` Jonathan Adams
2019-08-05 4:14 ` Minchan Kim [this message]
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