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Mon, 27 May 2024 13:54:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id I2w+H6WQVGYEFgAAD6G6ig (envelope-from ); Mon, 27 May 2024 13:54:45 +0000 Date: Mon, 27 May 2024 15:54:36 +0200 From: Oscar Salvador To: David Hildenbrand Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Muchun Song , Vishal Moola Subject: Re: [PATCH] mm/hugetlb: Move vmf_anon_prepare upfront in hugetlb_wp Message-ID: References: <20240521073446.23185-1-osalvador@suse.de> <9f3371fa-0d46-4e93-a00b-0f5cb30b58bb@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9f3371fa-0d46-4e93-a00b-0f5cb30b58bb@redhat.com> X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: EF7521C000E X-Stat-Signature: i4w54p59og6ttxnj1sa71mcz5tspxxea X-HE-Tag: 1716818087-950829 X-HE-Meta: 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 mKuLHVF8 tTD4C4UyffqaX/dwUq1sVHrBx9rLVUUTeafdGwoSkruWRnIgfcWjCkY1peKMeZJ0qePV+KIdSA8G03FbvZJ5bmWPV2voJR2kVRjb561PySilgTUNked2+LVfaRPAbg0oo4XfqKLOCyFt6h9zGuTzeh98tznHh2nfd02s3UMlQGUFCiZb+OxPx6NGWM+Ot4oqZI5R5+GdiCMH0iT0waaN3gNkUYS5eBNRYnKo+iUZoU/4sYYmTUGbtXUL5+JC7+jMNaaA/zMIi2h/iwXeb6jZI/UQsaYi8os1bgeyW4kEBnOym/iHuMzwuLWWQc8S9nhVS4e9uUh1PFqUVQ46RnWJQUj0A+b0EV8rDT7P6p7ESL1HSfmwqSJ9ePg9yMvq/YScXtxHvoUAcm2GdjCSzIMQJDxp5/TklmNdYVOIA5TCfKRzeVkw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, 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 Mon, May 27, 2024 at 03:17:01PM +0200, David Hildenbrand wrote: > gup_must_unshare() without a VMA is only used for GUP-fast. Before > triggering a page fault we always fallback to GUP-slow first, where we have > a VMA. I see, thanks for explaining! > IMHO we better not make assumptions that hugetlb_wp() will always already > have an anon VMA. Fine by me, I just wanted to have the picture more clear, because I could not see how we could end up in such situation, but better be safe and than sorry. @Andrew: This fix is to avoid an issue like [1], but for hugetlb_wp(). [1] https://lore.kernel.org/linux-mm/000000000000daf1e10615e64dcb@google.com/T/ -- Oscar Salvador SUSE Labs