linux-kernel - Re: [PATCH RFC 01/13] mm/rmap: fix missing swap_free() in try_to_unmap() after arch_unmap

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Message-ID: <e1c1a037-9782-dead-fcfe-e6be318069fa@oracle.com>
Date:   Thu, 24 Feb 2022 09:26:44 -0700
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Yang Shi <shy828301@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Nadav Amit <namit@...are.com>, Rik van Riel <riel@...riel.com>,
        Roman Gushchin <guro@...com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Donald Dutile <ddutile@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Oleg Nesterov <oleg@...hat.com>, Jan Kara <jack@...e.cz>,
        Liang Zhang <zhangliang5@...wei.com>,
        Pedro Gomes <pedrodemargomes@...il.com>,
        Oded Gabbay <oded.gabbay@...il.com>, linux-mm@...ck.org
Subject: Re: [PATCH RFC 01/13] mm/rmap: fix missing swap_free() in
 try_to_unmap() after arch_unmap_one() failed

On 2/24/22 05:26, David Hildenbrand wrote:
> In case arch_unmap_one() fails, we already did a swap_duplicate(). let's
> undo that properly via swap_free().
> 
> Fixes: ca827d55ebaa ("mm, swap: Add infrastructure for saving page metadata on swap")
> Cc: Khalid Aziz <khalid.aziz@...cle.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>   mm/rmap.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 6a1e8c7f6213..f825aeef61ca 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1625,6 +1625,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
>   				break;
>   			}
>   			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
> +				swap_free(entry);
>   				set_pte_at(mm, address, pvmw.pte, pteval);
>   				ret = false;
>   				page_vma_mapped_walk_done(&pvmw);

That looks reasonable.

Reviewed-by: Khalid Aziz <khalid.aziz@...cle.com>

--
Khalid