On Mon, 9 Jul 2012, Michal Hocko wrote:

Maybe I am missing something but who does the uncharge from:
shmem_unuse
  mem_cgroup_cache_charge
  shmem_unuse_inode
    shmem_add_to_page_cache

There isn't any special uncharge for shmem_unuse(): once the swapcache
page is matched up with its memcg, it will get uncharged by one of the
usual routes to swapcache_free() when the page is freed: maybe in the
call from __remove_mapping(), maybe when free_page_and_swap_cache()
ends up calling it.

Perhaps you're worrying about error (or unfound) paths in shmem_unuse()?
By the time we make the charge, we know for sure that it's a shmem page,
and make the charge appropriately; in racy cases it might get uncharged
again in the delete_from_swap_cache().  Can the unfound case occur these
days?  I'd have to think more deeply to answer that, but the charge will
not go missing.

Hugh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>