Oleg Nesterov <[email protected]> writes: > 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. > > The patch also extracts the "inode is dead" code > from pid_delete_dentry(dentry) into the new trivial helper, > proc_inode_is_dead(inode), proc_task_readdir() uses it to return > -ENOENT if this dir was removed. This is a bit racy, but the race > is very inlikely and the getdents() after openndir() can see the > empty "." + ".." dir only once.
This version looks good. I especially like the factoring out of proc_inode_is_dead, that makes the purpose of that code much clearer. Reviewed-by: "Eric W. Biederman" <[email protected]> > Signed-off-by: Oleg Nesterov <[email protected]> > --- > fs/proc/base.c | 53 ++++++++++++++++++++++------------------------------- > 1 files changed, 22 insertions(+), 31 deletions(-) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index bed1096..5e0e02f 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -1652,13 +1652,18 @@ int pid_revalidate(struct dentry *dentry, unsigned > int flags) > return 0; > } > > +static inline bool proc_inode_is_dead(struct inode *inode) > +{ > + return !proc_pid(inode)->tasks[PIDTYPE_PID].first; > +} > + > int pid_delete_dentry(const struct dentry *dentry) > { > /* Is the task we represent dead? > * If so, then don't put the dentry on the lru list, > * kill it immediately. > */ > - return !proc_pid(dentry->d_inode)->tasks[PIDTYPE_PID].first; > + return proc_inode_is_dead(dentry->d_inode); > } > > const struct dentry_operations pid_dentry_operations = > @@ -3173,34 +3178,35 @@ 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 +3253,13 @@ 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 (proc_inode_is_dead(inode)) > + return -ENOENT; > > switch ((unsigned long)filp->f_pos) { > case 0: > @@ -3289,7 +3282,7 @@ 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 +3295,7 @@ 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
