On Wed, Jan 26, 2011 at 12:29:15AM -0800, Greg Thelen wrote: > mem_cgroup_get_limit() returns a byte limit as a unsigned 64 bit value, > which is converted to a page count by mem_cgroup_out_of_memory(). Prior > to this patch the conversion could overflow on 32 bit platforms > yielding a limit of zero. Balbir: It can truncate, because the conversion shrinks the required bits of this 64-bit number by only PAGE_SHIFT (12). Trying to store the resulting up to 52 significant bits in a 32-bit integer will cut up to 20 significant bits off. > Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx> > --- > mm/oom_kill.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 7dcca55..3fcac51 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -538,7 +538,7 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask) > struct task_struct *p; > > check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL); > - limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT; > + limit = min(mem_cgroup_get_limit(mem) >> PAGE_SHIFT, (u64)ULONG_MAX); I would much prefer using min_t(u64, ...). To make it really, really explicit that this is 64-bit arithmetic. But that is just me, no correctness issue. Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>