linux-kernel - Re: [RFC PATCH v2 14/16] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline

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Date:   Mon, 21 Oct 2019 09:20:46 +0000
From:   Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:     Oscar Salvador <osalvador@...e.de>
CC:     "mhocko@...nel.org" <mhocko@...nel.org>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2 14/16] mm,hwpoison: Return 0 if the page is
 already poisoned in soft-offline

On Thu, Oct 17, 2019 at 04:21:21PM +0200, Oscar Salvador wrote:
> Currently, there is an inconsistency when calling soft-offline from
> different paths on a page that is already poisoned.
> 
> 1) madvise:
> 
>         madvise_inject_error skips any poisoned page and continues
>         the loop.
>         If that was the only page to madvise, it returns 0.
> 
> 2) /sys/devices/system/memory/:
> 
>         Whe calling soft_offline_page_store()->soft_offline_page(),
>         we return -EBUSY in case the page is already poisoned.
>         This is inconsistent with a) the above example and b)
>         memory_failure, where we return 0 if the page was poisoned.
> 
> Fix this by dropping the PageHWPoison() check in madvise_inject_error,
> and let soft_offline_page return 0 if it finds the page already poisoned.
> 
> Please, note that this represents an user-api change, since now the return
> error when calling soft_offline_page_store()->soft_offline_page() will be different.
> 
> Signed-off-by: Oscar Salvador <osalvador@...e.de>

Looks good to me.

Acked-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>

> ---
>  mm/madvise.c        | 3 ---
>  mm/memory-failure.c | 4 ++--
>  2 files changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 8a0b1f901d72..9ca48345ce45 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -887,9 +887,6 @@ static int madvise_inject_error(int behavior,
>  		 */
>  		put_page(page);
>  
> -		if (PageHWPoison(page))
> -			continue;
> -
>  		if (behavior == MADV_SOFT_OFFLINE) {
>  			pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
>  				 pfn, start);
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 3d491c0d3f91..c038896bedf0 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1767,7 +1767,7 @@ static int __soft_offline_page(struct page *page)
>  		unlock_page(page);
>  		put_page(page);
>  		pr_info("soft offline: %#lx page already poisoned\n", pfn);
> -		return -EBUSY;
> +		return 0;
>  	}
>  
>  	if (!PageHuge(page))
> @@ -1866,7 +1866,7 @@ int soft_offline_page(struct page *page)
>  
>  	if (PageHWPoison(page)) {
>  		pr_info("soft offline: %#lx page already poisoned\n", pfn);
> -		return -EBUSY;
> +		return 0;
>  	}
>  
>  	get_online_mems();
> -- 
> 2.12.3
> 
>