On Thu, Apr 09, 2020 at 11:22:14PM +0200, Miklos Szeredi wrote:
> @@ -1249,42 +1277,50 @@ struct vfsmount *mnt_clone_internal(cons
> static void *m_start(struct seq_file *m, loff_t *pos)
> {
> struct proc_mounts *p = m->private;
> + struct mount *mnt = NULL;
>
> down_read(&namespace_sem);
> - if (p->cached_event == p->ns->event) {
> - void *v = p->cached_mount;
> - if (*pos == p->cached_index)
> - return v;
> - if (*pos == p->cached_index + 1) {
> - v = seq_list_next(v, &p->ns->list, &p->cached_index);
> - return p->cached_mount = v;
> - }
> - }
> + lock_ns_list(p->ns);
> + if (!*pos)
> + list_move(&p->cursor.mnt_list, &p->ns->list);
> + if (!list_empty(&p->cursor.mnt_list))
> + mnt = mnt_skip_cursors(p->ns, &p->cursor);
> + unlock_ns_list(p->ns);
Huh? What's that if (!list_empty()) about? The case where we have reached
the end of list, then did a read() with an lseek() in between?
If so, then this is out of place under your spinlock; "is on the list"
state changes only synchronously (seq_file ->lock serializes all of
that). *If* this is what you've meant, I'd suggest
/* read after we'd reached the end? */
if (*pos && list_empty(...))
return NULL;
lock_ns_list(p->ns);
if (!*pos)
list_move(...); /* rewind on lseek or initial read */
mnt = mnt_skip_cursors(...);
unlock_ns_list(p->ns);
Or am I misreading your intent there? Confused...
