Messages in this thread | | | From | Greg Thelen <> | Date | Mon, 8 Nov 2010 19:52:20 -0800 | Subject | Re: [PATCH] memcg: avoid overflow in memcg_hierarchical_free_pages() |
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On Mon, Nov 8, 2010 at 7:44 PM, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote: > On Mon, 8 Nov 2010 17:15:20 -0800 > Greg Thelen <gthelen@google.com> wrote: > >> Use page counts rather than byte counts to avoid overflowing >> unsigned long local variables. >> >> Signed-off-by: Greg Thelen <gthelen@google.com> >> --- >> mm/memcontrol.c | 10 +++++----- >> 1 files changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 6c7115d..b287afd 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -1345,17 +1345,17 @@ memcg_hierarchical_free_pages(struct mem_cgroup *mem) >> { >> unsigned long free, min_free; >> > hmm, the default value of RES_LIMIT is LLONG_MAX, so I think we must declare > "free" as unsinged long long to avoid overflow.
Agreed. I am testing a fix for that issue now. I do not want complicate this patch with the RES_LIMIT issue you mention. The fix will be in a separate patch.
> Thanks, > Daisuke Nishimura. > >> - min_free = global_page_state(NR_FREE_PAGES) << PAGE_SHIFT; >> + min_free = global_page_state(NR_FREE_PAGES); >> >> while (mem) { >> - free = res_counter_read_u64(&mem->res, RES_LIMIT) - >> - res_counter_read_u64(&mem->res, RES_USAGE); >> + free = (res_counter_read_u64(&mem->res, RES_LIMIT) - >> + res_counter_read_u64(&mem->res, RES_USAGE)) >> >> + PAGE_SHIFT; >> min_free = min(min_free, free); >> mem = parent_mem_cgroup(mem); >> } >> >> - /* Translate free memory in pages */ >> - return min_free >> PAGE_SHIFT; >> + return min_free; >> } >> >> /* >> -- >> 1.7.3.1 >> > -- 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/
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