From 5b42360c73b0679505dac6ec44d234cfec61120c Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Fri, 28 Apr 2023 13:24:05 +0000 Subject: memcg: use seq_buf_do_printk() with mem_cgroup_print_oom_meminfo() Currently, we format all the memcg stats into a buffer in mem_cgroup_print_oom_meminfo() and use pr_info() to dump it to the logs. However, this buffer is large in size. Although it is currently working as intended, ther is a dependency between the memcg stats buffer and the printk record size limit. If we add more stats in the future and the buffer becomes larger than the printk record size limit, or if the prink record size limit is reduced, the logs may be truncated. It is safer to use seq_buf_do_printk(), which will automatically break up the buffer at line breaks and issue small printk() calls. Refactor the code to move the seq_buf from memory_stat_format() to its callers, and use seq_buf_do_printk() to print the seq_buf in mem_cgroup_print_oom_meminfo(). Link: https://lkml.kernel.org/r/20230428132406.2540811-2-yosryahmed@google.com Signed-off-by: Yosry Ahmed Acked-by: Michal Hocko Reviewed-by: Sergey Senozhatsky Acked-by: Shakeel Butt Reviewed-by: Muchun Song Cc: Johannes Weiner Cc: Michal Hocko Cc: Petr Mladek Cc: Roman Gushchin Cc: Steven Rostedt (Google) Signed-off-by: Andrew Morton --- mm/memcontrol.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1e364ad495a3..a79a47f7fc20 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1580,13 +1580,10 @@ static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg, return memcg_page_state(memcg, item) * memcg_page_state_unit(item); } -static void memory_stat_format(struct mem_cgroup *memcg, char *buf, int bufsize) +static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) { - struct seq_buf s; int i; - seq_buf_init(&s, buf, bufsize); - /* * Provide statistics on the state of the memory subsystem as * well as cumulative event counters that show past behavior. @@ -1603,21 +1600,21 @@ static void memory_stat_format(struct mem_cgroup *memcg, char *buf, int bufsize) u64 size; size = memcg_page_state_output(memcg, memory_stats[i].idx); - seq_buf_printf(&s, "%s %llu\n", memory_stats[i].name, size); + seq_buf_printf(s, "%s %llu\n", memory_stats[i].name, size); if (unlikely(memory_stats[i].idx == NR_SLAB_UNRECLAIMABLE_B)) { size += memcg_page_state_output(memcg, NR_SLAB_RECLAIMABLE_B); - seq_buf_printf(&s, "slab %llu\n", size); + seq_buf_printf(s, "slab %llu\n", size); } } /* Accumulated memory events */ - seq_buf_printf(&s, "pgscan %lu\n", + seq_buf_printf(s, "pgscan %lu\n", memcg_events(memcg, PGSCAN_KSWAPD) + memcg_events(memcg, PGSCAN_DIRECT) + memcg_events(memcg, PGSCAN_KHUGEPAGED)); - seq_buf_printf(&s, "pgsteal %lu\n", + seq_buf_printf(s, "pgsteal %lu\n", memcg_events(memcg, PGSTEAL_KSWAPD) + memcg_events(memcg, PGSTEAL_DIRECT) + memcg_events(memcg, PGSTEAL_KHUGEPAGED)); @@ -1627,13 +1624,13 @@ static void memory_stat_format(struct mem_cgroup *memcg, char *buf, int bufsize) memcg_vm_event_stat[i] == PGPGOUT) continue; - seq_buf_printf(&s, "%s %lu\n", + seq_buf_printf(s, "%s %lu\n", 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)); + WARN_ON_ONCE(seq_buf_has_overflowed(s)); } #define K(x) ((x) << (PAGE_SHIFT-10)) @@ -1671,6 +1668,7 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) { /* Use static buffer, for the caller is holding oom_lock. */ static char buf[PAGE_SIZE]; + struct seq_buf s; lockdep_assert_held(&oom_lock); @@ -1693,8 +1691,9 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) pr_info("Memory cgroup stats for "); pr_cont_cgroup_path(memcg->css.cgroup); pr_cont(":"); - memory_stat_format(memcg, buf, sizeof(buf)); - pr_info("%s", buf); + seq_buf_init(&s, buf, sizeof(buf)); + memory_stat_format(memcg, &s); + seq_buf_do_printk(&s, KERN_INFO); } /* @@ -6635,10 +6634,12 @@ static int memory_stat_show(struct seq_file *m, void *v) { struct mem_cgroup *memcg = mem_cgroup_from_seq(m); char *buf = kmalloc(PAGE_SIZE, GFP_KERNEL); + struct seq_buf s; if (!buf) return -ENOMEM; - memory_stat_format(memcg, buf, PAGE_SIZE); + seq_buf_init(&s, buf, PAGE_SIZE); + memory_stat_format(memcg, &s); seq_puts(m, buf); kfree(buf); return 0; -- cgit v1.2.3