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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1to3KR-000000033wq-1NiW; Fri, 28 Feb 2025 16:35:16 +0000 Date: Fri, 28 Feb 2025 16:35:11 +0000 From: Matthew Wilcox To: Zi Yan Cc: Liu Shixin , Baolin Wang , linux-mm@kvack.org, Andrew Morton , Barry Song , David Hildenbrand , Kefeng Wang , Lance Yang , Ryan Roberts , Hugh Dickins , Charan Teja Kalla , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/migrate: fix shmem xarray update during migration Message-ID: References: <20250228154219.2214149-1-ziy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250228154219.2214149-1-ziy@nvidia.com> X-Stat-Signature: 93y7nktb4shnnrhcrwhbcjr5iwdy7ndc X-Rspamd-Queue-Id: 130BF80025 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1740760535-584834 X-HE-Meta: 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 j0S0J4j5 09E2dVzK+uTTbvh+iebJk240So4mUfX5g0kcpTyxmfdgZnKkycJPj0WrvBHpxazMCNOafXTdrPkvyiMT6r//e5SDsjj4JqsSxSSS+6T3z0+3wk1nTHYJYu7IPZoc4GtjH/sZGBN3uNDB6v3/TPsHqtwFM6jyFJ2OUVB2Hv0mWA46x0QrV86HXkQM6q3BKSPlbPevvY3XD6QOLrdx5tiV5n48bziUaNDkpizhuXl/oqfQnln4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 >