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Wed, 26 Feb 2025 08:23:09 -0800 (PST) MIME-Version: 1.0 References: <20250225204613.2316092-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 26 Feb 2025 08:22:58 -0800 X-Gm-Features: AWEUYZl0Odoo1BBPR51MmJxbUsSi0fMIUcQ-Z4sIaMMNc_DMaCdMCu8Iy33_Mg0 Message-ID: Subject: Re: [PATCH 1/1] userfaultfd: do not block on locking a large folio with raised refcount To: Matthew Wilcox Cc: "Liam R. Howlett" , akpm@linux-foundation.org, lokeshgidra@google.com, aarcange@redhat.com, 21cnbao@gmail.com, v-songbaohua@oppo.com, david@redhat.com, peterx@redhat.com, lorenzo.stoakes@oracle.com, hughd@google.com, jannh@google.com, kaleshsingh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: AAA4340011 X-Stat-Signature: 39yk4xwe8ebnwwoe3afskmuqndco1zp3 X-HE-Tag: 1740586990-892523 X-HE-Meta: U2FsdGVkX1/iWnchz5zyFbuqz7uzps+T+M+V7i1QdwKYJBLuVvQ4hm8CxpUzQbwaz9peSEsAhVBNryzJRopZ+reI8Jf/ThHWvlSRgd4z18duRirvTdLirBfwgaV+BIR6qS8FPWmg8GO7oyEfveUs1AYDOyjfsXfYywQvI+qiyQyeEcNEyUNgjEgKoUrKtBlmf8aaUDuxf3ArKlE4Meir7poRxtDQ++JvZdsCpwfdtYo/0w+I6fwXyajxO35X0nzUY3ksx6W/5RxeDz/GW87vvKbN4u6TVQtPJ72qxAhKtSe984PoK1Cip3G4K1Go/UBP5pZLz5APSe+n/Bu71SCoURiCNTjwIyfVv6tNSefz1ZNeXGhrX9jeZzoycjhkiAFFhVRwBUFypYJFOjLTfrVLPCNbTLlb3qwSUOtIXQZEq9aZE471d8OCQR3ZqPMHygYewp+unDUfu1ZOPlAYCJvHlbOzgH0CHsFwOGO2UsF/iYQKrFQ5ABTVGQmOjbNm39IUm/ZTmJQcDacV9FfbTLs4tIkofM06eNIfctZFwwviTZJpcB5qN9mvDzebyx1az8m3YAgCzYuJDePLXg92mlEo5f+XDlNtogJluYu7BiFfgZrK+7CZ1EXIrjyYxQCNFq1aM/yDQ5LFblwQsP2ZeKvY4S7ccYz/+OtN5PcvWzywHAulDM+6nDkqwulixHoI2VF10Ogc36W5m+ZBZKwItVjYQQfTSpjKtLnfJ59AMwvqj1FOVE/zYRQwjPMf8Jl+KxIRJukmmFVng80xH4jQrl3QDy2buWSldGzXuGXMz8Q+JFmfv4sXYdQVqpdjSWdTx5DOvunFUbrI1EaNbaJmGcLilK+kJkQq7RkUY/17ThZ/k02uyBMP1D9KlfUMzn9tYVTzq1dco+giRxDiMF+VSfbsSFQ3K6vOwnADwDGd0VousbpDSF3f3anbOTblUB+VuyLyyGevQwStzDisOgQJBb2 HfM8OoyY 6T71jAzBdLOS7w5Itu92ozpmNEFQ8EaFP7bxJ2QcWTJa2uj1FIbKi+YuaAeChvHf0DlkWt+DFXGYaAWMx3SoQ9h5adFVpzkJY9kNjir4VwaFP4M+RawCScI9c/vlodLPJGyf9yTkfKcQKxUkpsP3lEd8Fq0UsT+wKQavtlL6Y8NQIkgsI+MfbI4oxbkoLzx6R3AQ8e4/uXikITyzyu8aOrJIOWPW7OGHhmUh3At0qGI6yUQer4ogWvWiE/+SEUhZitnmKGwXemzAHMNbB7VAY7KoP9w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000061, 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, Feb 26, 2025 at 8:16=E2=80=AFAM Matthew Wilcox wrote: > > On Wed, Feb 26, 2025 at 08:11:25AM -0800, Suren Baghdasaryan wrote: > > On Wed, Feb 26, 2025 at 6:59=E2=80=AFAM Liam R. Howlett wrote: > > > Reversing the locking/folio_get() is okay because of the src_ptl spin > > > lock, right? It might be worth saying something about it in the > > > comment? > > > > That is correct. We take both folio lock and refcount before we drop > > PTL. I'll add a comment. Thanks! > > In the commit message, not in the code, please. Ack.