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Biederman" , Mike Rapoport , Geert Uytterhoeven , Anshuman Khandual , "Aneesh Kumar K.V" , Daniel Axtens , Jonathan Marek , Christophe Leroy , Pasha Tatashin , Peter Xu , Andrea Arcangeli , Thomas Gleixner , Andy Lutomirski , Sebastian Andrzej Siewior , Fenghua Yu , David Hildenbrand , linux-kernel@vger.kernel.org, Kaiyang Zhao , Huichun Feng , Jim Huang Subject: [RFC PATCH 2/6] mm: clone3: Add CLONE_COW_PGTABLE flag Date: Fri, 20 May 2022 02:31:23 +0800 Message-Id: <20220519183127.3909598-3-shiyn.lin@gmail.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220519183127.3909598-1-shiyn.lin@gmail.com> References: <20220519183127.3909598-1-shiyn.lin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 2084B1200E9 X-Stat-Signature: hxcg8gc41p87a4nikkaakxmafur861ha Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=I+QLZYTC; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf29.hostedemail.com: domain of shiyn.lin@gmail.com designates 209.85.214.174 as permitted sender) smtp.mailfrom=shiyn.lin@gmail.com X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1652985008-288060 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: Add CLONE_COW_PGTABLE flag to support clone3() system call to enable the Copy-On-Write (COW) mechanism on the page table. Signed-off-by: Chih-En Lin --- include/uapi/linux/sched.h | 1 + kernel/fork.c | 6 +++++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 3bac0a8ceab2..3b92ff589e0f 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -36,6 +36,7 @@ /* Flags for the clone3() syscall. */ #define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and reset to SIG_DFL. */ #define CLONE_INTO_CGROUP 0x200000000ULL /* Clone into a specific cgroup given the right permissions. */ +#define CLONE_COW_PGTABLE 0x400000000ULL /* Copy-On-Write for page table */ /* * cloning flags intersect with CSIGNAL so can be used with unshare and clone3 diff --git a/kernel/fork.c b/kernel/fork.c index 35a3beff140b..08cf95201333 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2636,6 +2636,9 @@ pid_t kernel_clone(struct kernel_clone_args *args) trace = 0; } + if (clone_flags & CLONE_COW_PGTABLE) + set_bit(MMF_COW_PGTABLE, ¤t->mm->flags); + p = copy_process(NULL, trace, NUMA_NO_NODE, args); add_latent_entropy(); @@ -2860,7 +2863,8 @@ static bool clone3_args_valid(struct kernel_clone_args *kargs) { /* Verify that no unknown flags are passed along. */ if (kargs->flags & - ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP)) + ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP | + CLONE_COW_PGTABLE)) return false; /* -- 2.36.1