Messages in this thread | | | Date | Tue, 24 Feb 2009 09:10:34 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [RFC][PATCH] Reduce size of swap_cgroup by CSS ID v2 |
| |
On Mon, 23 Feb 2009 14:58:28 +0900 Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> I'm sorry for my late reply. > > It looks good basically, but I have 1 comment. > > > static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page) > > { > > - struct mem_cgroup *mem; > > + unsigned short id; > > + struct mem_cgroup *mem = NULL; > > swp_entry_t ent; > > > > if (!PageSwapCache(page)) > > return NULL; > > > > ent.val = page_private(page); > > - mem = lookup_swap_cgroup(ent); > > - if (!mem) > > - return NULL; > > + id = lookup_swap_cgroup(ent); > > + rcu_read_lock(); > > + mem = mem_cgroup_lookup(id); > > if (!css_tryget(&mem->css)) > We should check whether "mem" is NULL or not before css_tryget, because > "mem" can be NULL(or "id" can be 0) if the page is on swapcache, > that is, remove_from_swap_cache has not been called yet. > > Actually, I got NULL pointer dereference bug here. > Okay, will fix.
Thanks, -kame
> > - return NULL; > > + mem = NULL; > > + rcu_read_unlock(); > > return mem; > > } > > > > > Thanks, > Daisuke Nishimura. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
| |