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Thu, 16 Apr 2026 09:27:19 -0400 (EDT) Date: Thu, 16 Apr 2026 14:27:17 +0100 From: Kiryl Shutsemau To: Usama Arif Cc: Andrew Morton , Peter Xu , David Hildenbrand , Lorenzo Stoakes , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , "Liam R . Howlett" , Zi Yan , Jonathan Corbet , Shuah Khan , Sean Christopherson , Paolo Bonzini , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [RFC, PATCH 10/12] userfaultfd: add UFFDIO_SET_MODE for runtime sync/async toggle Message-ID: References: <20260414142354.1465950-11-kas@kernel.org> <20260415150900.3660575-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260415150900.3660575-1-usama.arif@linux.dev> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A58B980002 X-Stat-Signature: r9w3wr3zdb3ojno61kd11954sayuqgaj X-Rspam-User: X-HE-Tag: 1776346043-628633 X-HE-Meta: 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 TB5X5ujC CWwQuS8TKuftIiws1b5wl0eHtSjSQ1Ca786PupPIqtHgN74/XHB3avbOufdOWgNGRsisA1Q8nPDZCVydzu12Pgh2RI9NE9tAGl1JfxtfYe1NpnUZcII0Hw/p3MjIPCVZcZsiadx5g/OmjsTUjSfY6L8z0+qvp8ASZYbvMXbefQYeimvqpSzXVV1iX59Iql2WdjSlMGInmk/qj+WzCjuWheqjTigykqrQYXyrz04TGlFMlzScTCJSuO6FxqjPAgJaKrOytfYNk+sRj3URDjppxeMFlY/mQ5UuetwQC1owindHmdXUlX3poqc453AypHi+4gzSY/6GlSxDxmI3URIFV5VphGtE0fjrrLB0c Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 15, 2026 at 08:08:59AM -0700, Usama Arif wrote: > > + /* only toggleable features are allowed */ > > + if ((mode.enable | mode.disable) & ~UFFD_FEATURE_TOGGLEABLE) > > + return -EINVAL; > > The commit message states "Only async features that were enabled at > UFFDIO_API time may be toggled." However, the code only checks that > the requested feature is in UFFD_FEATURE_TOGGLEABLE. > > Is it intentional that a user who opened a uffd without > UFFD_FEATURE_MINOR_ASYNC can still enable it later via > UFFDIO_SET_MODE? The comment is stale. Will fix. -- Kiryl Shutsemau / Kirill A. Shutemov