KAMEZAWA Hiroyuki wrote:
> The logic of uncharging is
> - decrement refcnt -> lock page cgroup -> remove page cgroup.
> But the logic of charging is
> - lock page cgroup -> increment refcnt -> return.
>
> Then, one charge will be added to a page_cgroup under being removed.
> This makes no big trouble (like panic) but one charge is lost.
>
> This patch add a test at charging to verify page_cgroup's refcnt is
> greater than 0. If not, unlock and retry.
>
> Signed-off-by: KAMEZAWA Hiroyuki <[EMAIL PROTECTED]>
>
>
> mm/memcontrol.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> Index: linux-2.6.23-rc8-mm2/mm/memcontrol.c
> ===================================================================
> --- linux-2.6.23-rc8-mm2.orig/mm/memcontrol.c
> +++ linux-2.6.23-rc8-mm2/mm/memcontrol.c
> @@ -271,14 +271,19 @@ int mem_cgroup_charge(struct page *page,
> * to see if the cgroup page already has a page_cgroup associated
> * with it
> */
> +retry:
> lock_page_cgroup(page);
> pc = page_get_page_cgroup(page);
> /*
> * The page_cgroup exists and the page has already been accounted
> */
> if (pc) {
> - atomic_inc(&pc->ref_cnt);
> - goto done;
> + if (unlikely(!atomic_inc_not_zero(&pc->ref_cnt))) {
> + /* this page is under being uncharge ? */
> + unlock_page_cgroup(page);
> + goto retry;
> + } else
> + goto done;
> }
>
> unlock_page_cgroup(page);
>
>
Looks good to me
Acked-by: Balbir Singh <[EMAIL PROTECTED]>
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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