[PATCH v2 3/8] mm/memcontrol.c: Convert to printbuf

Kent Overstreet
2022-04-21T23:49:25Z

This converts memory_stat_format() from seq_buf to printbuf. Printbuf is
simalar to seq_buf except that it heap allocates the string buffer:
here, we were already heap allocating the buffer with kmalloc() so the
conversion is trivial.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
---
mm/memcontrol.c | 68 ++++++++++++++++++++++++-------------------------
1 file changed, 33 insertions(+), 35 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 36e9f38c91..4cb0b7bc1c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -61,7 +61,7 @@
#include <linux/file.h>
#include <linux/tracehook.h>
#include <linux/psi.h>
-#include <linux/seq_buf.h>
+#include <linux/printbuf.h>
#include "internal.h"
#include <net/sock.h>
#include <net/ip.h>
@@ -1436,13 +1436,9 @@ static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg,

static char *memory_stat_format(struct mem_cgroup *memcg)
{
- struct seq_buf s;
+ struct printbuf buf = PRINTBUF;
int i;

- seq_buf_init(&s, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE);
- if (!s.buffer)
- return NULL;
-
/*
* Provide statistics on the state of the memory subsystem as
* well as cumulative event counters that show past behavior.
@@ -1459,49 +1455,51 @@ static char *memory_stat_format(struct mem_cgroup *memcg)
u64 size;

size = memcg_page_state_output(memcg, memory_stats[i].idx);
- seq_buf_printf(&s, "%s %llu\n", memory_stats[i].name, size);
+ pr_buf(&buf, "%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);
+ pr_buf(&buf, "slab %llu\n", size);
}
}

/* Accumulated memory events */

- seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGFAULT),
- memcg_events(memcg, PGFAULT));
- seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGMAJFAULT),
- memcg_events(memcg, PGMAJFAULT));
- seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGREFILL),
- memcg_events(memcg, PGREFILL));
- seq_buf_printf(&s, "pgscan %lu\n",
- memcg_events(memcg, PGSCAN_KSWAPD) +
- memcg_events(memcg, PGSCAN_DIRECT));
- seq_buf_printf(&s, "pgsteal %lu\n",
- memcg_events(memcg, PGSTEAL_KSWAPD) +
- memcg_events(memcg, PGSTEAL_DIRECT));
- seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGACTIVATE),
- memcg_events(memcg, PGACTIVATE));
- seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGDEACTIVATE),
- memcg_events(memcg, PGDEACTIVATE));
- seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGLAZYFREE),
- memcg_events(memcg, PGLAZYFREE));
- seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGLAZYFREED),
- memcg_events(memcg, PGLAZYFREED));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(PGFAULT),
+ memcg_events(memcg, PGFAULT));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(PGMAJFAULT),
+ memcg_events(memcg, PGMAJFAULT));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(PGREFILL),
+ memcg_events(memcg, PGREFILL));
+ pr_buf(&buf, "pgscan %lu\n",
+ memcg_events(memcg, PGSCAN_KSWAPD) +
+ memcg_events(memcg, PGSCAN_DIRECT));
+ pr_buf(&buf, "pgsteal %lu\n",
+ memcg_events(memcg, PGSTEAL_KSWAPD) +
+ memcg_events(memcg, PGSTEAL_DIRECT));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(PGACTIVATE),
+ memcg_events(memcg, PGACTIVATE));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(PGDEACTIVATE),
+ memcg_events(memcg, PGDEACTIVATE));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(PGLAZYFREE),
+ memcg_events(memcg, PGLAZYFREE));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(PGLAZYFREED),
+ memcg_events(memcg, PGLAZYFREED));

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- seq_buf_printf(&s, "%s %lu\n", vm_event_name(THP_FAULT_ALLOC),
- memcg_events(memcg, THP_FAULT_ALLOC));
- seq_buf_printf(&s, "%s %lu\n", vm_event_name(THP_COLLAPSE_ALLOC),
- memcg_events(memcg, THP_COLLAPSE_ALLOC));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(THP_FAULT_ALLOC),
+ memcg_events(memcg, THP_FAULT_ALLOC));
+ pr_buf(&buf, "%s %lu\n", vm_event_name(THP_COLLAPSE_ALLOC),
+ memcg_events(memcg, THP_COLLAPSE_ALLOC));
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

- /* The above should easily fit into one page */
- WARN_ON_ONCE(seq_buf_has_overflowed(&s));
+ if (buf.allocation_failure) {
+ printbuf_exit(&buf);
+ return NULL;
+ }

- return s.buffer;
+ return buf.buf;
}

#define K(x) ((x) << (PAGE_SHIFT-10))
--
2.35.2