linux-kernel - Re: [BUGFIX][PATCH mmotm] memcg fix swap accounting leak (v3)

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Date:	Mon, 15 Dec 2008 10:34:26 +0000 (GMT)
From:	Hugh Dickins <hugh@...itas.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [BUGFIX][PATCH mmotm] memcg fix swap accounting leak (v3)

On Mon, 15 Dec 2008, KAMEZAWA Hiroyuki wrote:
> 
> Fix swapin charge operation of memcg.
> 
> @@ -1139,10 +1139,11 @@ void mem_cgroup_commit_charge_swapin(str
>  	/*
>  	 * Now swap is on-memory. This means this page may be
>  	 * counted both as mem and swap....double count.
> -	 * Fix it by uncharging from memsw. This SwapCache is stable
> -	 * because we're still under lock_page().
> +	 * Fix it by uncharging from memsw. Basically, this SwapCache is stable
> +	 * under lock_page(). But in do_swap_page()::memory.c, reuse_swap_page()
> +	 * may call delete_from_swap_cache() before reach here.
>  	 */
> -	if (do_swap_account) {
> +	if (do_swap_account && PageSwapCache(page)) {
>  		swp_entry_t ent = {.val = page_private(page)};
>  		struct mem_cgroup *memcg;
>  		memcg = swap_cgroup_record(ent, NULL);

Yes, that addition looks good to me.

Hugh
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