[patch] mm: memcontrol: default hierarchy interface for memory fix - "none"

From: Johannes Weiner
Date: Sat Jan 17 2015 - 10:21:56 EST

The "none" name for the low-boundary 0 and the high-boundary maximum
value can be confusing.

Just leave the low boundary at 0, and give the highest-possible
boundary value the name "max" that means the same for controls.

Reported-by: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
Documentation/cgroups/unified-hierarchy.txt | 5 +--
include/linux/page_counter.h | 3 +-
mm/memcontrol.c | 58 ++++++++++-------------------
mm/page_counter.c | 9 ++++-
4 files changed, 31 insertions(+), 44 deletions(-)

diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
index 643af9bb9a07..171aa23c113e 100644
--- a/Documentation/cgroups/unified-hierarchy.txt
+++ b/Documentation/cgroups/unified-hierarchy.txt
@@ -404,9 +404,8 @@ supported and the interface files "release_agent" and
be understood as an underflow into the highest possible value, -2 or
-10M etc. do not work, so it's not consistent.

- memory.low and memory.high will indicate "none" if the boundary is
- not configured, and a configured boundary can be unset by writing
- "none" into these files as well.
+ memory.low, memory.high, and memory.max will use the string "max" to
+ indicate and configure the highest possible value.

5. Planned Changes

diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h
index 955421575d16..17fa4f8de3a6 100644
--- a/include/linux/page_counter.h
+++ b/include/linux/page_counter.h
@@ -41,7 +41,8 @@ int page_counter_try_charge(struct page_counter *counter,
struct page_counter **fail);
void page_counter_uncharge(struct page_counter *counter, unsigned long nr_pages);
int page_counter_limit(struct page_counter *counter, unsigned long limit);
-int page_counter_memparse(const char *buf, unsigned long *nr_pages);
+int page_counter_memparse(const char *buf, const char *max,
+ unsigned long *nr_pages);

static inline void page_counter_reset_watermark(struct page_counter *counter)
{
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7adccee9fecb..718bc6bb5837 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3419,13 +3419,9 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
int ret;

buf = strstrip(buf);
- if (!strcmp(buf, "-1")) {
- nr_pages = PAGE_COUNTER_MAX;
- } else {
- ret = page_counter_memparse(buf, &nr_pages);
- if (ret)
- return ret;
- }
+ ret = page_counter_memparse(buf, "-1", &nr_pages);
+ if (ret)
+ return ret;

switch (MEMFILE_ATTR(of_cft(of)->private)) {
case RES_LIMIT:
@@ -3795,13 +3791,9 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
unsigned long usage;
int i, size, ret;

- if (!strcmp(args, "-1")) {
- threshold = PAGE_COUNTER_MAX;
- } else {
- ret = page_counter_memparse(args, &threshold);
- if (ret)
- return ret;
- }
+ ret = page_counter_memparse(args, "-1", &threshold);
+ if (ret)
+ return ret;

mutex_lock(&memcg->thresholds_lock);

@@ -5246,8 +5238,8 @@ static int memory_low_show(struct seq_file *m, void *v)
struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
unsigned long low = ACCESS_ONCE(memcg->low);

- if (low == 0)
- seq_puts(m, "none\n");
+ if (low == PAGE_COUNTER_MAX)
+ seq_puts(m, "max\n");
else
seq_printf(m, "%llu\n", (u64)low * PAGE_SIZE);

@@ -5262,13 +5254,9 @@ static ssize_t memory_low_write(struct kernfs_open_file *of,
int err;

buf = strstrip(buf);
- if (!strcmp(buf, "none")) {
- low = 0;
- } else {
- err = page_counter_memparse(buf, &low);
- if (err)
- return err;
- }
+ err = page_counter_memparse(buf, "max", &low);
+ if (err)
+ return err;

memcg->low = low;

@@ -5281,7 +5269,7 @@ static int memory_high_show(struct seq_file *m, void *v)
unsigned long high = ACCESS_ONCE(memcg->high);

if (high == PAGE_COUNTER_MAX)
- seq_puts(m, "none\n");
+ seq_puts(m, "max\n");
else
seq_printf(m, "%llu\n", (u64)high * PAGE_SIZE);

@@ -5296,13 +5284,9 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
int err;

buf = strstrip(buf);
- if (!strcmp(buf, "none")) {
- high = PAGE_COUNTER_MAX;
- } else {
- err = page_counter_memparse(buf, &high);
- if (err)
- return err;
- }
+ err = page_counter_memparse(buf, "max", &high);
+ if (err)
+ return err;

memcg->high = high;

@@ -5315,7 +5299,7 @@ static int memory_max_show(struct seq_file *m, void *v)
unsigned long max = ACCESS_ONCE(memcg->memory.limit);

if (max == PAGE_COUNTER_MAX)
- seq_puts(m, "none\n");
+ seq_puts(m, "max\n");
else
seq_printf(m, "%llu\n", (u64)max * PAGE_SIZE);

@@ -5330,13 +5314,9 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,
int err;

buf = strstrip(buf);
- if (!strcmp(buf, "none")) {
- max = PAGE_COUNTER_MAX;
- } else {
- err = page_counter_memparse(buf, &max);
- if (err)
- return err;
- }
+ err = page_counter_memparse(buf, "max", &max);
+ if (err)
+ return err;

err = mem_cgroup_resize_limit(memcg, max);
if (err)
diff --git a/mm/page_counter.c b/mm/page_counter.c
index 0d4f9daf68bd..11b4beda14ba 100644
--- a/mm/page_counter.c
+++ b/mm/page_counter.c
@@ -166,16 +166,23 @@ int page_counter_limit(struct page_counter *counter, unsigned long limit)
/**
* page_counter_memparse - memparse() for page counter limits
* @buf: string to parse
+ * @max: string meaning maximum possible value
* @nr_pages: returns the result in number of pages
*
* Returns -EINVAL, or 0 and @nr_pages on success. @nr_pages will be
* limited to %PAGE_COUNTER_MAX.
*/
-int page_counter_memparse(const char *buf, unsigned long *nr_pages)
+int page_counter_memparse(const char *buf, const char *max,
+ unsigned long *nr_pages)
{
char *end;
u64 bytes;

+ if (!strcmp(buf, max)) {
+ *nr_pages = PAGE_COUNTER_MAX;
+ return 0;
+ }
+
bytes = memparse(buf, &end);
if (*end != '\0')
return -EINVAL;
--
2.2.0

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