From: Jann Horn <jannh@google.com>
To: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, Eric Biederman <ebiederm@xmission.com>,
Oleg Nesterov <oleg@redhat.com>
Cc: linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
Kees Cook <keescook@chromium.org>, Ingo Molnar <mingo@kernel.org>
Subject: [RFC PATCH resend 5/6] ptrace: Use mm_ref() for ->exit_mm
Date: Sat, 17 Oct 2020 01:09:14 +0200 [thread overview]
Message-ID: <20201016230915.1972840-6-jannh@google.com> (raw)
In-Reply-To: <20201016230915.1972840-1-jannh@google.com>
We only use ->exit_mm to look up dumpability and the ->user_mm; we don't
need to keep the PGD alive for this.
mmgrab() is also inconvenient here, because it means that we need to use
mmdrop_async() when dropping the reference to the mm from an RCU callback.
Use mm_ref() instead of mmgrab() to make things neater.
Signed-off-by: Jann Horn <jannh@google.com>
---
kernel/exit.c | 2 +-
kernel/fork.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c
index 97253ef33486..03ba6d13ef1e 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -476,7 +476,7 @@ static void exit_mm(void)
/* more a memory barrier than a real lock */
task_lock(current);
current->mm = NULL;
- mmgrab(mm); /* for current->exit_mm */
+ mm_ref(mm); /* for current->exit_mm */
current->exit_mm = mm;
mmap_read_unlock(mm);
enter_lazy_tlb(mm, current);
diff --git a/kernel/fork.c b/kernel/fork.c
index 59c119b03351..4383bf055b40 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -720,7 +720,7 @@ void free_task(struct task_struct *tsk)
if (tsk->flags & PF_KTHREAD)
free_kthread_struct(tsk);
if (tsk->exit_mm)
- mmdrop_async(tsk->exit_mm);
+ mm_unref(tsk->exit_mm);
free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);
--
2.29.0.rc1.297.gfa9743e501-goog
next prev parent reply other threads:[~2020-10-16 23:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-16 23:09 [RFC PATCH resend 0/6] mm and ptrace: Track dumpability until task is freed Jann Horn
2020-10-16 23:09 ` [RFC PATCH resend 1/6] ptrace: Keep mm around after exit_mm() for __ptrace_may_access() Jann Horn
2020-10-16 23:09 ` [RFC PATCH resend 2/6] refcount: Move refcount_t definition into linux/types.h Jann Horn
2020-10-16 23:09 ` [RFC PATCH resend 3/6] mm: Add refcount for preserving mm_struct without pgd Jann Horn
2020-10-16 23:21 ` Jason Gunthorpe
2020-10-17 0:30 ` Jann Horn
2020-11-03 2:11 ` Jann Horn
2020-11-03 3:19 ` Jann Horn
2020-11-03 13:21 ` Jason Gunthorpe
2020-11-03 19:18 ` John Hubbard
2020-10-16 23:09 ` [RFC PATCH resend 4/6] mm, oom: Use mm_ref()/mm_unref() and avoid mmdrop_async() Jann Horn
2020-10-16 23:09 ` Jann Horn [this message]
2020-10-16 23:09 ` [RFC PATCH resend 6/6] mm: remove now-unused mmdrop_async() Jann Horn
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