linux-kernel - Re: [PATCH v1 2/5] mm: add full variable in swap_info

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Date:	Mon, 22 Sep 2014 13:45:22 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Dan Streetman <ddstreet@...e.org>,
	Nitin Gupta <ngupta@...are.org>,
	Luigi Semenzato <semenzato@...gle.com>, juno.choi@....com
Subject: Re: [PATCH v1 2/5] mm: add full variable in swap_info_struct

On Mon, 22 Sep 2014 09:03:08 +0900 Minchan Kim <minchan@...nel.org> wrote:

> Now, swap leans on !p->highest_bit to indicate a swap is full.
> It works well for normal swap because every slot on swap device
> is used up when the swap is full but in case of zram, swap sees
> still many empty slot although backed device(ie, zram) is full
> since zram's limit is over so that it could make trouble when
> swap use highest_bit to select new slot via free_cluster.
> 
> This patch introduces full varaiable in swap_info_struct
> to solve the problem.
> 
> ...
>
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -224,6 +224,7 @@ struct swap_info_struct {
>  	struct swap_cluster_info free_cluster_tail; /* free cluster list tail */
>  	unsigned int lowest_bit;	/* index of first free in swap_map */
>  	unsigned int highest_bit;	/* index of last free in swap_map */
> +	bool	full;			/* whether swap is full or not */

This is protected by swap_info_struct.lock, I worked out.

There's a large comment at swap_info_struct.lock which could be updated.


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