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Wed, 26 Feb 2025 10:59:12 -0800 (PST) MIME-Version: 1.0 References: <20250225204613.2316092-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 26 Feb 2025 10:59:01 -0800 X-Gm-Features: AWEUYZnMlDxNde9kN15MMA6yX02fUGcPfWxSIB1NIXSIYDSCauDYwoderXQdXBk 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-Queue-Id: D6EC912000D X-Stat-Signature: h9bcyz9tmcqh7bs3inbdb5n3moncpaby X-Rspamd-Server: rspam03 X-HE-Tag: 1740596354-306158 X-HE-Meta: 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 dDj2gUmf WXyrCfpjDyIaTgHWVW0PUWjmG7sns6fjMQHpTze5N/oly6bQNeXbGX92lCpj3bXeiQVXROl1c2RRaBBFPDMEVBfQUF0Xad9rLVGVpMSB1Wph+uTlBVhP2Wz1XiFZkJhtiyEzjZfF4OnK1yjHGlRgPzKyXjUBBENgH9t9ZqpKgif1EETC912mC7iXaeztjRzh8Gcz5aVL2UMOA4WUSR2eACDflOS90P+Ztivxknl8hj4vk5KAeEGXu4YMtmk5FAlnDyvp8YuAdFk1ctEM8iHK6xiSWx26alSQ+JPpvpZxlmz29x58OTaxBaLo1Y2KAcXJVN+gjM2vy1BqfNss= 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, Feb 26, 2025 at 8:22=E2=80=AFAM Suren Baghdasaryan wrote: > > 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 sp= in > > > > 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. I posted v2 at https://lore.kernel.org/all/20250226185510.2732648-2-surenb@= google.com/ as part of a pachset which includes the fix for PTE unmapping that Peter reported. Patchset is rebased over mm-hotfixes-unstable which includes Barry's fix to the nearby code. This avoids merge conflicts.