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Wed, 22 Jul 2026 05:51:44 -0700 (PDT) Received: from intel.company.local ([210.184.73.204]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-38ea78484b8sm1021162a91.4.2026.07.22.05.51.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Jul 2026 05:51:43 -0700 (PDT) From: Wandun Chen To: liam@infradead.org, ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, vbabka@kernel.org, jannh@google.com, pfalcato@suse.de Subject: [PATCH] mm/mlock: skip __mm_populate() for MLOCK_ONFAULT Date: Wed, 22 Jul 2026 20:51:33 +0800 Message-ID: <20260722125133.543441-1-chenwandun1@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Wandun Chen MLOCK_ONFAULT only locks pages on future faults, so there is no need to fault in non-present pages during the mlock2/mlockall syscall. populate_vma_page_range() already returns immediately for VMAs with VM_LOCKONFAULT, which means __mm_populate() just loops over VMAs and holds mmap_read_lock without doing useful work. Skip __mm_populate() when MLOCK_ONFAULT is set to avoid this unnecessary work. Signed-off-by: Wandun Chen --- mm/mlock.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/mlock.c b/mm/mlock.c index efa6716e4dfb..784bd4bfc3bb 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -658,9 +658,11 @@ static __must_check int do_mlock(unsigned long start, = size_t len, if (error) return error; =20 - error =3D __mm_populate(start, len, 0); - if (error) - return __mlock_posix_error_return(error); + if (!vma_flags_test(flags, VMA_LOCKONFAULT_BIT)) { + error =3D __mm_populate(start, len, 0); + if (error) + return __mlock_posix_error_return(error); + } return 0; } =20 @@ -778,7 +780,7 @@ SYSCALL_DEFINE1(mlockall, int, flags) capable(CAP_IPC_LOCK)) ret =3D apply_mlockall_flags(flags); mmap_write_unlock(current->mm); - if (!ret && (flags & MCL_CURRENT)) + if (!ret && (flags & MCL_CURRENT) && !(flags & MCL_ONFAULT)) mm_populate(0, TASK_SIZE); =20 return ret; --=20 2.43.0