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Date: Tue, 17 Mar 2026 11:01:04 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "Lorenzo Stoakes (Oracle)" <ljs@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>, Yosry Ahmed <yosry@kernel.org>,
 Nhat Pham <nphamcs@gmail.com>, Chengming Zhou <chengming.zhou@linux.dev>,
 linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH mm-hotfixes] mm/zswap: add missing kunmap_local()
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On Tue, 17 Mar 2026 12:59:35 +0000 "Lorenzo Stoakes (Oracle)" <ljs@kernel.org> wrote:

> Hi Andrew,
> 
> Please apply the fix-patch enclosed to add a dcache flush which was also
> missing here.
> 
> ...
>

That was a lot of sleuthing.

> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -950,6 +950,7 @@ static bool zswap_decompress(struct zswap_entry *entry, struct folio *folio)
>  		memcpy_from_sglist(dst, input, 0, PAGE_SIZE);
>  		dlen = PAGE_SIZE;
>  		kunmap_local(dst);
> +		flush_dcache_folio(folio);
>  	} else {
>  		sg_init_table(&output, 1);
>  		sg_set_folio(&output, folio, PAGE_SIZE, 0);

Which will all be lost when I squash the patch, unless someone follows
the Link: which I add to the footer when squashing.

How about I copy your sleuthing into the base patch changelog to
capture the reasoning for the flush_dcache_folio()'s presence?