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From: Matthew Wilcox <willy@infradead.org>
To: Zi Yan <ziy@nvidia.com>
Cc: Liu Shixin <liushixin2@huawei.com>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Barry Song <baohua@kernel.org>,
	David Hildenbrand <david@redhat.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	Lance Yang <ioworker0@gmail.com>,
	Ryan Roberts <ryan.roberts@arm.com>,
	Hugh Dickins <hughd@google.com>,
	Charan Teja Kalla <quic_charante@quicinc.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/migrate: fix shmem xarray update during migration
Date: Fri, 28 Feb 2025 16:35:11 +0000	[thread overview]
Message-ID: <Z8HlvyKod4pbi6le@casper.infradead.org> (raw)
In-Reply-To: <20250228154219.2214149-1-ziy@nvidia.com>

On Fri, Feb 28, 2025 at 10:42:19AM -0500, Zi Yan wrote:
> @@ -524,7 +525,11 @@ static int __folio_migrate_mapping(struct address_space *mapping,
>  			folio_set_swapcache(newfolio);
>  			newfolio->private = folio_get_private(folio);
>  		}
> -		entries = nr;
> +		/* shmem uses high-order entry */
> +		if (shmem_mapping(mapping))

It's be cheaper to check folio_test_anon() here, right?

Also, how did this bug remain unnoticed for almost 4 years?
Our testing is terrible ;-(

> +			entries = 1;
> +		else
> +			entries = nr;
>  	} else {
>  		VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
>  		entries = 1;
> -- 
> 2.47.2
> 


  reply	other threads:[~2025-02-28 16:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-02-28 15:42 Zi Yan
2025-02-28 16:35 ` Matthew Wilcox [this message]
2025-02-28 17:05   ` Zi Yan
2025-02-28 17:02 ` Shivank Garg
2025-02-28 17:17   ` Zi Yan

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