linux-kernel - Re: [PATCH] mm,hwpoison: Return -EBUSY when migration fails

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Message-ID: <a30f4786-7c54-9fa8-0d39-6ae4d10f93c2@redhat.com>
Date:   Wed, 9 Dec 2020 10:59:04 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Oscar Salvador <osalvador@...e.de>, akpm@...ux-foundation.org
Cc:     n-horiguchi@...jp.nec.com, vbabka@...e.cz, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm,hwpoison: Return -EBUSY when migration fails

On 09.12.20 10:28, Oscar Salvador wrote:
> Currently, we return -EIO when we fail to migrate the page.
> 
> Migrations' failures are rather transient as they can happen due to
> several reasons, e.g: high page refcount bump, mapping->migrate_page
> failing etc.
> All meaning that at that time the page could not be migrated, but
> that has nothing to do with an EIO error.
> 
> Let us return -EBUSY instead, as we do in case we failed to isolate
> the page.
> 
> While are it, let us remove the "ret" print as its value does not change.
> 
> Signed-off-by: Oscar Salvador <osalvador@...e.de>
> ---
>  mm/memory-failure.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 428991e297e2..1942fb83ac64 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1849,11 +1849,11 @@ static int __soft_offline_page(struct page *page)
>  			pr_info("soft offline: %#lx: %s migration failed %d, type %lx (%pGp)\n",
>  				pfn, msg_page[huge], ret, page->flags, &page->flags);
>  			if (ret > 0)
> -				ret = -EIO;
> +				ret = -EBUSY;

Do we expect callers to retry immediately? -EAGAIN might make also
sense. But -EBUSY is an obvious improvement. Do we have callers relying
on this behavior?


-- 
Thanks,

David / dhildenb