The patch titled
Subject: memcg: use seq_buf_do_printk() with mem_cgroup_print_oom_meminfo()
has been added to the -mm mm-unstable branch. Its filename is
memcg-use-seq_buf_do_printk-with-mem_cgroup_print_oom_meminfo.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-use-seq_buf_do_printk-with-mem_cgroup_print_oom_meminfo.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Subject: memcg: use seq_buf_do_printk() with mem_cgroup_print_oom_meminfo()
Date: Fri, 28 Apr 2023 13:24:05 +0000
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@xxxxxxxxxx
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)
--- a/mm/memcontrol.c~memcg-use-seq_buf_do_printk-with-mem_cgroup_print_oom_meminfo
+++ a/mm/memcontrol.c
@@ -1580,13 +1580,10 @@ static inline unsigned long memcg_page_s
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 me
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 me
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
{
/* 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
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_f
{
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;
_
Patches currently in -mm which might be from yosryahmed@xxxxxxxxxx are
memcg-use-seq_buf_do_printk-with-mem_cgroup_print_oom_meminfo.patch
memcg-dump-memorystat-during-cgroup-oom-for-v1.patch
