On Thu, 8 Dec 2011 16:18:29 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > commit ef6a3c6311 adds a function replace_page_cache_page(). This > function replaces a page in radix-tree with a new page. > At doing this, memory cgroup need to fix up the accounting information. > memcg need to check PCG_USED bit etc. > > In some(many?) case, 'newpage' is on LRU before calling replace_page_cache(). > So, memcg's LRU accounting information should be fixed, too. > > This patch adds mem_cgroup_replace_page_cache() and removing old hooks. > In that function, old pages will be unaccounted without touching res_counter > and new page will be accounted to the memcg (of old page). At overwriting > pc->mem_cgroup of newpage, take zone->lru_lock and avoid race with > LRU handling. > > Background: > replace_page_cache_page() is called by FUSE code in its splice() handling. > Here, 'newpage' is replacing oldpage but this newpage is not a newly allocated > page and may be on LRU. LRU mis-accounting will be critical for memory cgroup > because rmdir() checks the whole LRU is empty and there is no account leak. > If a page is on the other LRU than it should be, rmdir() will fail. > > Changelog: v1 -> v2 > - fixed mem_cgroup_disabled() check missing. > - added comments. > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > --- > include/linux/memcontrol.h | 6 ++++++ > mm/filemap.c | 18 ++---------------- > mm/memcontrol.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 52 insertions(+), 16 deletions(-) It's a relatively intrusive patch and I'm a bit concerned about feeding it into 3.2. How serious is the bug, and which kernel version(s) do you think we should fix it in? -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
