Messages in this thread Patch in this message | | | Date | Mon, 27 May 2013 22:28:22 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 3/3] proc: simplify proc_task_readdir/first_tid paths |
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proc_task_readdir() does not really need "leader", first_tid() has to revalidate it anyway. Just pass proc_pid(inode) to first_tid() instead, it can do pid_task(PIDTYPE_PID) itself and read ->group_leader only if necessary.
Note: I am not sure proc_task_readdir() really needs the initial -ENOENT check, but this is what the current code does.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- fs/proc/base.c | 46 ++++++++++++++++------------------------------ 1 files changed, 16 insertions(+), 30 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c index bed1096..dbc4dae 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3173,34 +3173,35 @@ out_no_task: * In the case of a seek we start with the leader and walk nr * threads past it. */ -static struct task_struct *first_tid(struct task_struct *leader, - int tid, int nr, struct pid_namespace *ns) +static struct task_struct *first_tid(struct pid *pid, int tid, + int nr, struct pid_namespace *ns) { - struct task_struct *pos; + struct task_struct *pos, *task; rcu_read_lock(); - /* Attempt to start with the pid of a thread */ + task = pid_task(pid, PIDTYPE_PID); + if (!task) + goto fail; + + /* Attempt to start with the tid of a thread */ if (tid && (nr > 0)) { pos = find_task_by_pid_ns(tid, ns); - if (pos && (pos->group_leader == leader)) + if (pos && same_thread_group(pos, task)) goto found; } /* If nr exceeds the number of threads there is nothing todo */ - if (nr && nr >= get_nr_threads(leader)) - goto fail; - /* It could be unhashed before we take rcu lock */ - if (!pid_alive(leader)) + if (nr && nr >= get_nr_threads(task)) goto fail; /* If we haven't found our starting place yet start * with the leader and walk nr threads forward. */ - pos = leader; + pos = task = task->group_leader; do { if (nr-- <= 0) goto found; - } while_each_thread(leader, pos); + } while_each_thread(task, pos); fail: pos = NULL; goto out; @@ -3247,26 +3248,13 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi { struct dentry *dentry = filp->f_path.dentry; struct inode *inode = dentry->d_inode; - struct task_struct *leader = NULL; struct task_struct *task; - int retval = -ENOENT; ino_t ino; int tid; struct pid_namespace *ns; - task = get_proc_task(inode); - if (!task) - goto out_no_task; - rcu_read_lock(); - if (pid_alive(task)) { - leader = task->group_leader; - get_task_struct(leader); - } - rcu_read_unlock(); - put_task_struct(task); - if (!leader) - goto out_no_task; - retval = 0; + if (!pid_task(proc_pid(inode), PIDTYPE_PID)) + return -ENOENT; switch ((unsigned long)filp->f_pos) { case 0: @@ -3289,7 +3277,7 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi ns = filp->f_dentry->d_sb->s_fs_info; tid = (int)filp->f_version; filp->f_version = 0; - for (task = first_tid(leader, tid, filp->f_pos - 2, ns); + for (task = first_tid(proc_pid(inode), tid, filp->f_pos - 2, ns); task; task = next_tid(task), filp->f_pos++) { tid = task_pid_nr_ns(task, ns); @@ -3302,9 +3290,7 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi } } out: - put_task_struct(leader); -out_no_task: - return retval; + return 0; } static int proc_task_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat) -- 1.5.5.1
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