On 2024/6/27 15:13, Michal Hocko wrote: > On Wed 26-06-24 09:42:32, Xiu Jianfeng wrote: >> Both the end of memory_stat_format() and memcg_stat_format() will call >> WARN_ON_ONCE(seq_buf_has_overflowed()). However, memory_stat_format() >> is the only caller of memcg_stat_format(), when memcg is on the default >> hierarchy, seq_buf_has_overflowed() will be executed twice, so remove >> the reduntant one. > > Shouldn't we rather remove both? Are they giving us anything useful > actually? Would a simpl pr_warn be sufficient? Afterall all we care > about is to learn that we need to grow the buffer size because our stats > do not fit anymore. It is not really important whether that is an OOM or > cgroupfs interface path. I did a test, when I removed both of them and added a lot of prints in memcg_stat_format() to make the seq_buf overflow, and then cat memory.stat in user mode, no OOM occurred, and there were no warning logs in the kernel. > >> Signed-off-by: Xiu Jianfeng <xiujianfeng@xxxxxxxxxx> >> --- >> mm/memcontrol.c | 3 --- >> 1 file changed, 3 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 974bd160838c..776d22bc66a2 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -1846,9 +1846,6 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) >> vm_event_name(memcg_vm_event_stat[i]), >> memcg_events(memcg, memcg_vm_event_stat[i])); >> } >> - >> - /* The above should easily fit into one page */ >> - WARN_ON_ONCE(seq_buf_has_overflowed(s)); >> } >> >> static void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s); >> -- >> 2.34.1 >
