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From: David Herrmann <dh.herrmann@gmail.com>
Date: Mon, 20 Apr 2015 11:13:54 +0200
Subject: [PATCH] kdbus: no need to ref current->mm
If we access current->mm temporarily, there is no need to ref it. It can
only be changed by us, so no-one can race with us.
Avoid ref'ing and unref'ing it just to access some of its fields, similar
to what syscalls in mm/ do.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
---
ipc/kdbus/metadata.c | 21 +++------------------
1 file changed, 3 insertions(+), 18 deletions(-)
diff --git a/ipc/kdbus/metadata.c b/ipc/kdbus/metadata.c
index a85eac34a5c4..c36b9cc67637 100644
--- a/ipc/kdbus/metadata.c
+++ b/ipc/kdbus/metadata.c
@@ -282,15 +282,10 @@ static void kdbus_meta_proc_collect_pid_comm(struct kdbus_meta_proc *mp)
static void kdbus_meta_proc_collect_exe(struct kdbus_meta_proc *mp)
{
- struct mm_struct *mm;
struct file *exe_file;
- mm = get_task_mm(current);
- if (!mm)
- return;
-
rcu_read_lock();
- exe_file = rcu_dereference(mm->exe_file);
+ exe_file = rcu_dereference(current->mm->exe_file);
if (exe_file) {
mp->exe_path = exe_file->f_path;
path_get(&mp->exe_path);
@@ -298,28 +293,18 @@ static void kdbus_meta_proc_collect_exe(struct kdbus_meta_proc *mp)
mp->valid |= KDBUS_ATTACH_EXE;
}
rcu_read_unlock();
-
- mmput(mm);
}
static int kdbus_meta_proc_collect_cmdline(struct kdbus_meta_proc *mp)
{
- struct mm_struct *mm;
+ struct mm_struct *mm = current->mm;
char *cmdline;
- mm = get_task_mm(current);
- if (!mm)
- return 0;
-
- if (!mm->arg_end) {
- mmput(mm);
+ if (!mm->arg_end)
return 0;
- }
cmdline = strndup_user((const char __user *)mm->arg_start,
mm->arg_end - mm->arg_start);
- mmput(mm);
-
if (IS_ERR(cmdline))
return PTR_ERR(cmdline);
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