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Date: Tue, 20 Dec 2022 15:27:30 +0800
From: Chih-En Lin <shiyn.lin@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Qi Zheng <zhengqi.arch@...edance.com>,
David Hildenbrand <david@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Christophe Leroy <christophe.leroy@...roup.eu>,
John Hubbard <jhubbard@...dia.com>,
Nadav Amit <namit@...are.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Yang Shi <shy828301@...il.com>, Peter Xu <peterx@...hat.com>,
Zach O'Keefe <zokeefe@...gle.com>,
"Liam R . Howlett" <Liam.Howlett@...cle.com>,
Alex Sierra <alex.sierra@....com>,
Xianting Tian <xianting.tian@...ux.alibaba.com>,
Colin Cross <ccross@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Barry Song <baohua@...nel.org>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Suleiman Souhlal <suleiman@...gle.com>,
Brian Geffon <bgeffon@...gle.com>, Yu Zhao <yuzhao@...gle.com>,
Tong Tiangen <tongtiangen@...wei.com>,
Liu Shixin <liushixin2@...wei.com>,
Li kunyu <kunyu@...china.com>,
Anshuman Khandual <anshuman.khandual@....com>,
Vlastimil Babka <vbabka@...e.cz>,
Hugh Dickins <hughd@...gle.com>,
Minchan Kim <minchan@...nel.org>,
Miaohe Lin <linmiaohe@...wei.com>,
Gautam Menghani <gautammenghani201@...il.com>,
Catalin Marinas <catalin.marinas@....com>,
Mark Brown <broonie@...nel.org>, Will Deacon <will@...nel.org>,
"Eric W . Biederman" <ebiederm@...ssion.com>,
Thomas Gleixner <tglx@...utronix.de>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Andy Lutomirski <luto@...nel.org>,
Fenghua Yu <fenghua.yu@...el.com>,
Barret Rhoden <brho@...gle.com>,
Davidlohr Bueso <dave@...olabs.net>,
"Jason A . Donenfeld" <Jason@...c4.com>,
Dinglan Peng <peng301@...due.edu>,
Pedro Fonseca <pfonseca@...due.edu>,
Jim Huang <jserv@...s.ncku.edu.tw>,
Huichun Feng <foxhoundsk.tw@...il.com>,
Chih-En Lin <shiyn.lin@...il.com>
Subject: [PATCH v3 01/14] mm: Allow user to control COW PTE via prctl
Add a new prctl, PR_SET_COW_PTE, to allow the user to enable COW PTE.
Since it has a time gap between using the prctl to enable the COW PTE
and doing the fork, we use two states (MMF_COW_PTE_READY and MMF_COW_PTE)
to determine the task that wants to do COW PTE or already doing it.
The MMF_COW_PTE_READY flag marks the task to do COW PTE in the next time
of fork(). During fork(), if MMF_COW_PTE_READY set, fork() will unset the
flag and set the MMF_COW_PTE flag. After that, fork() might shares PTEs
instead of duplicates it.
Signed-off-by: Chih-En Lin <shiyn.lin@...il.com>
---
include/linux/sched/coredump.h | 12 +++++++++++-
include/uapi/linux/prctl.h | 6 ++++++
kernel/sys.c | 11 +++++++++++
3 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h
index 8270ad7ae14c2..570d599ebc851 100644
--- a/include/linux/sched/coredump.h
+++ b/include/linux/sched/coredump.h
@@ -83,7 +83,17 @@ static inline int get_dumpable(struct mm_struct *mm)
#define MMF_HAS_PINNED 27 /* FOLL_PIN has run, never cleared */
#define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP)
+/*
+ * MMF_COW_PTE_READY: Marking the task to do COW PTE in the next time of
+ * fork(). During fork(), if MMF_COW_PTE_READY set, fork() will unset the
+ * flag and set the MMF_COW_PTE flag. After that, fork() might shares PTEs
+ * rather than duplicates it.
+ */
+#define MMF_COW_PTE_READY 29 /* Share PTE tables in next time of fork() */
+#define MMF_COW_PTE 30 /* PTE tables are shared between processes */
+#define MMF_COW_PTE_MASK (1 << MMF_COW_PTE)
+
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\
- MMF_DISABLE_THP_MASK)
+ MMF_DISABLE_THP_MASK | MMF_COW_PTE_MASK)
#endif /* _LINUX_SCHED_COREDUMP_H */
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index a5e06dcbba136..664a3c0230192 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -284,4 +284,10 @@ struct prctl_mm_map {
#define PR_SET_VMA 0x53564d41
# define PR_SET_VMA_ANON_NAME 0
+/*
+ * Set the prepare flag, MMF_COW_PTE_READY, to do the share (copy-on-write)
+ * page table in the next time of fork.
+ */
+#define PR_SET_COW_PTE 65
+
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 5fd54bf0e8867..d1062ea33981e 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2348,6 +2348,14 @@ static int prctl_set_vma(unsigned long opt, unsigned long start,
}
#endif /* CONFIG_ANON_VMA_NAME */
+static int prctl_set_cow_pte(struct mm_struct *mm)
+{
+ if (test_bit(MMF_COW_PTE, &mm->flags))
+ return -EINVAL;
+ set_bit(MMF_COW_PTE_READY, &mm->flags);
+ return 0;
+}
+
SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
unsigned long, arg4, unsigned long, arg5)
{
@@ -2626,6 +2634,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_SET_VMA:
error = prctl_set_vma(arg2, arg3, arg4, arg5);
break;
+ case PR_SET_COW_PTE:
+ error = prctl_set_cow_pte(me->mm);
+ break;
default:
error = -EINVAL;
break;
--
2.37.3
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