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Wed, 25 Jun 2025 07:47:06 +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 3REgCXqpW2jNEAAAD6G6ig (envelope-from ); Wed, 25 Jun 2025 07:47:06 +0000 Date: Wed, 25 Jun 2025 09:47:00 +0200 From: Oscar Salvador To: David Hildenbrand Cc: Andrew Morton , Muchun Song , Peter Xu , Gavin Guo , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/5] mm,hugetlb: Sort out folio locking in the faulting path Message-ID: References: <20250620123014.29748-1-osalvador@suse.de> <20250620123014.29748-3-osalvador@suse.de> <35b03911-74c3-4626-aaa8-4c331c086f8f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <35b03911-74c3-4626-aaa8-4c331c086f8f@redhat.com> X-Rspamd-Queue-Id: 3BD32140004 X-Stat-Signature: h9pidtdy4mcz86u11kpzwfcnst9n5icy X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1750837627-637921 X-HE-Meta: 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 tmV8Acxs jVxTpt2iuAPgbriAGkQnHyY6z8L8JISvEDeQh/ZfPnxueHpqy6Aket+2pJvjtg0L9DCn8Q5c8eY5pf2n3NnlDbpQhfxyRkT6/dFmZvKtCHeAUYEF0mNQhoh1wzXVmKCJbh8gTNJ+qO2dWHrIyLQUYsyCKsGY1XbOkueWPe1WW/JNR/FpYWpWfIEN5EgwQ7QPtc/fmzDWzfiWbfuMnQ/aBx4c3UqmxSz2kz/L1EOs55AJ3Vzli+bbBqr1ziA2o71/8HA4guijL/eNXCwM= 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 Mon, Jun 23, 2025 at 04:11:38PM +0200, David Hildenbrand wrote: > > @@ -6801,13 +6810,24 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, > > /* Fallthrough to CoW */ > > } > > - /* hugetlb_wp() requires page locks of pte_page(vmf.orig_pte) */ > > - folio = page_folio(pte_page(vmf.orig_pte)); > > - folio_lock(folio); > > - folio_get(folio); > > - > > if (flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) { > > if (!huge_pte_write(vmf.orig_pte)) { > > + /* > > + * Anonymous folios need to be lock since hugetlb_wp() > > + * checks whether we can re-use the folio exclusively > > + * for us in case we are the only user of it. > > + */ > > Should we move that comment to hugetlb_wp() instead? And if we are already > doing this PTL unlock dance now, why not do it in hugetlb_wp() instead so we > can simplify this code? Yes, probably we can move it further up. Let me see how it would look. thanks! -- Oscar Salvador SUSE Labs