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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uUcsb-0000000Akti-2hai; Thu, 26 Jun 2025 03:02:25 +0000 Date: Thu, 26 Jun 2025 04:02:25 +0100 From: Matthew Wilcox To: "Vishal Moola (Oracle)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Jordan Rome , Andrew Morton Subject: Re: [RFC PATCH 1/3] mm/memory.c: convert __copy_remote_vm_str() to folios Message-ID: References: <20250625174841.1094510-1-vishal.moola@gmail.com> <20250625174841.1094510-2-vishal.moola@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 80929A0003 X-Stat-Signature: bkqds35h6w6qzs59d7hhidrs49s1ati1 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1750906948-545234 X-HE-Meta: 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 KQA4noW2 JnqN84QT9l9e2Y6kLHdqJqf8KcIATWp+WgcMmVDo/8Rs5y1+eHRqPKb11Q1PP0uzZt51yiMJNtixy8Z21oJw9b6Co5hlMOy5PcTqsu1A+6TMie3uq9Xo1tIhFimea+hFOYzt91CouiDNbqwmdNAyqsewYNMYO8xHQcaiT4pXhBZbb0B/ud4lDpTbNCpxRoL11ywCJ0HVY5esE115JHCqX/21VAIh+vZBdZ3gizWc+ckn9pvhGumivH2UNr17oJCp0lWUJ 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 Wed, Jun 25, 2025 at 07:00:22PM +0100, Matthew Wilcox wrote: > > + folio_offset = offset_in_folio(folio, addr); > > Umm. Not sure this is safe. A folio might be mapped misaligned, so > 'addr' might not give you the right offset within the folio. I think > you might need to use addr - (vma->vm_pgoff << PAGE_SHIFT). But I'd > defer to others here ... particularly when it comes to anonymous folios. Sorry, this calculation is obviously wrong. It should be something like the calculation in linear_page_index(), only without throwing away the bottom PAGE_SHIFT bits. But that's for file VMAs only, and I'm not sure what should be done for anon vmas. Possibly there is no way?