[PATCH 14/18] mm: memcontrol: prepare swap controller setup for integration

Johannes Weiner
2020-04-20T22:12:12Z

A few cleanups to streamline the swap controller setup:

- Replace the do_swap_account flag with cgroup_memory_noswap. This
brings it in line with other functionality that is usually available
unless explicitly opted out of - nosocket, nokmem.

- Remove the really_do_swap_account flag that stores the boot option
and is later used to switch the do_swap_account. It's not clear why
this indirection is/was necessary. Use do_swap_account directly.

- Minor coding style polishing

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/memcontrol.h | 2 +-
mm/memcontrol.c | 59 ++++++++++++++++++--------------------
mm/swap_cgroup.c | 4 +--
3 files changed, 31 insertions(+), 34 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 52eb6411cfee..d458f1d90aa4 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -560,7 +560,7 @@ struct mem_cgroup *mem_cgroup_get_oom_group(struct task_struct *victim,
void mem_cgroup_print_oom_group(struct mem_cgroup *memcg);

#ifdef CONFIG_MEMCG_SWAP
-extern int do_swap_account;
+extern bool cgroup_memory_noswap;
#endif

struct mem_cgroup *lock_page_memcg(struct page *page);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d5aee5577ff3..5558777023e7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -83,10 +83,14 @@ static bool cgroup_memory_nokmem;

/* Whether the swap controller is active */
#ifdef CONFIG_MEMCG_SWAP
-int do_swap_account __read_mostly;
+#ifdef CONFIG_MEMCG_SWAP_ENABLED
+bool cgroup_memory_noswap __read_mostly;
#else
-#define do_swap_account 0
-#endif
+bool cgroup_memory_noswap __read_mostly = 1;
+#endif /* CONFIG_MEMCG_SWAP_ENABLED */
+#else
+#define cgroup_memory_noswap 1
+#endif /* CONFIG_MEMCG_SWAP */

#ifdef CONFIG_CGROUP_WRITEBACK
static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq);
@@ -95,7 +99,7 @@ static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq);
/* Whether legacy memory+swap accounting is active */
static bool do_memsw_account(void)
{
- return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && do_swap_account;
+ return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_noswap;
}

#define THRESHOLDS_EVENTS_TARGET 128
@@ -6458,18 +6462,19 @@ int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask,
/*
* Every swap fault against a single page tries to charge the
* page, bail as early as possible. shmem_unuse() encounters
- * already charged pages, too. The USED bit is protected by
- * the page lock, which serializes swap cache removal, which
+ * already charged pages, too. page->mem_cgroup is protected
+ * by the page lock, which serializes swap cache removal, which
* in turn serializes uncharging.
*/
VM_BUG_ON_PAGE(!PageLocked(page), page);
if (compound_head(page)->mem_cgroup)
goto out;

- if (do_swap_account) {
+ if (!cgroup_memory_noswap) {
swp_entry_t ent = { .val = page_private(page), };
- unsigned short id = lookup_swap_cgroup_id(ent);
+ unsigned short id;

+ id = lookup_swap_cgroup_id(ent);
rcu_read_lock();
memcg = mem_cgroup_from_id(id);
if (memcg && !css_tryget_online(&memcg->css))
@@ -6944,7 +6949,7 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
struct mem_cgroup *memcg;
unsigned short oldid;

- if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) || !do_swap_account)
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) || cgroup_memory_noswap)
return 0;

memcg = page->mem_cgroup;
@@ -6988,7 +6993,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
struct mem_cgroup *memcg;
unsigned short id;

- if (!do_swap_account)
+ if (cgroup_memory_noswap)
return;

id = swap_cgroup_record(entry, 0, nr_pages);
@@ -7011,7 +7016,7 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
{
long nr_swap_pages = get_nr_swap_pages();

- if (!do_swap_account || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
+ if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
return nr_swap_pages;
for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg))
nr_swap_pages = min_t(long, nr_swap_pages,
@@ -7028,7 +7033,7 @@ bool mem_cgroup_swap_full(struct page *page)

if (vm_swap_full())
return true;
- if (!do_swap_account || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
+ if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
return false;

memcg = page->mem_cgroup;
@@ -7043,22 +7048,15 @@ bool mem_cgroup_swap_full(struct page *page)
return false;
}

-/* for remember boot option*/
-#ifdef CONFIG_MEMCG_SWAP_ENABLED
-static int really_do_swap_account __initdata = 1;
-#else
-static int really_do_swap_account __initdata;
-#endif
-
-static int __init enable_swap_account(char *s)
+static int __init setup_swap_account(char *s)
{
if (!strcmp(s, "1"))
- really_do_swap_account = 1;
+ cgroup_memory_noswap = 0;
else if (!strcmp(s, "0"))
- really_do_swap_account = 0;
+ cgroup_memory_noswap = 1;
return 1;
}
-__setup("swapaccount=", enable_swap_account);
+__setup("swapaccount=", setup_swap_account);

static u64 swap_current_read(struct cgroup_subsys_state *css,
struct cftype *cft)
@@ -7124,7 +7122,7 @@ static struct cftype swap_files[] = {
{ } /* terminate */
};

-static struct cftype memsw_cgroup_files[] = {
+static struct cftype memsw_files[] = {
{
.name = "memsw.usage_in_bytes",
.private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
@@ -7153,13 +7151,12 @@ static struct cftype memsw_cgroup_files[] = {

static int __init mem_cgroup_swap_init(void)
{
- if (!mem_cgroup_disabled() && really_do_swap_account) {
- do_swap_account = 1;
- WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys,
- swap_files));
- WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys,
- memsw_cgroup_files));
- }
+ if (mem_cgroup_disabled() || cgroup_memory_noswap)
+ return 0;
+
+ WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, swap_files));
+ WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys, memsw_files));
+
return 0;
}
subsys_initcall(mem_cgroup_swap_init);
diff --git a/mm/swap_cgroup.c b/mm/swap_cgroup.c
index 45affaef3bc6..7aa764f09079 100644
--- a/mm/swap_cgroup.c
+++ b/mm/swap_cgroup.c
@@ -171,7 +171,7 @@ int swap_cgroup_swapon(int type, unsigned long max_pages)
unsigned long length;
struct swap_cgroup_ctrl *ctrl;

- if (!do_swap_account)
+ if (cgroup_memory_noswap)
return 0;

length = DIV_ROUND_UP(max_pages, SC_PER_PAGE);
@@ -209,7 +209,7 @@ void swap_cgroup_swapoff(int type)
unsigned long i, length;
struct swap_cgroup_ctrl *ctrl;

- if (!do_swap_account)
+ if (cgroup_memory_noswap)
return;

mutex_lock(&swap_cgroup_mutex);
--
2.26.0