linux-kernel - Re: [PATCH -next 1/1] mm/memory-failure.c: Cleanup in unpoison

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20221125085444.GA1230393@hori.linux.bs1.fc.nec.co.jp>
Date:   Fri, 25 Nov 2022 08:54:47 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Wupeng Ma <mawupeng1@...wei.com>
CC:     "linmiaohe@...wei.com" <linmiaohe@...wei.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "pizhenwei@...edance.com" <pizhenwei@...edance.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next 1/1] mm/memory-failure.c: Cleanup in unpoison_memory

On Fri, Nov 25, 2022 at 02:54:44PM +0800, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@...wei.com>
> 
> If freeit it true, the value of ret must be zero, there is no need to
> check the value of freeit after label unlock_mutex.
> 
> We can drop variable freeit to do this cleanup.
> 
> Signed-off-by: Ma Wupeng <mawupeng1@...wei.com>

Hi Wupeng,

> ---
>  mm/memory-failure.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 2e62940c7bae..c77a9e37e27e 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2338,7 +2338,6 @@ int unpoison_memory(unsigned long pfn)
>  	struct page *page;
>  	struct page *p;
>  	int ret = -EBUSY;
> -	int freeit = 0;
>  	unsigned long count = 1;
>  	bool huge = false;
>  	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
> @@ -2413,10 +2412,9 @@ int unpoison_memory(unsigned long pfn)
>  				goto unlock_mutex;
>  			}
>  		}
> -		freeit = !!TestClearPageHWPoison(p);
>  
>  		put_page(page);
> -		if (freeit) {
> +		if (TestClearPageHWPoison(p)) {

This reorders put_page() and TestClearPageHWPoison(), but when we run
into this else block, the target page or hugepage should have refcount > 1,
so it does not cause any behavioral change.  So I'm fine with it.

Looks good to me. Thank you for the patch.

Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>

>  			put_page(page);
>  			ret = 0;
>  		}
> @@ -2424,7 +2422,7 @@ int unpoison_memory(unsigned long pfn)
>  
>  unlock_mutex:
>  	mutex_unlock(&mf_mutex);
> -	if (!ret || freeit) {
> +	if (!ret) {
>  		if (!huge)
>  			num_poisoned_pages_sub(pfn, 1);
>  		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
> -- 
> 2.25.1