[PATCH v1 1/3] mm: memory-failure: Add memory failure stats to sysfs

[Jiaqi Yan <jiaqiyan@google.com>]

Today kernel provides following memory error info to userspace, but each
has its own disadvantage
* HardwareCorrupted in /proc/meminfo: number of bytes poisoned in total,
  not per NUMA node stats though
* ras:memory_failure_event: only available after explicitly enabled
* /dev/mcelog provides many useful info about the MCEs, but
  doesn't capture how memory_failure recovered memory MCEs
* kernel logs: userspace needs to process log text

Exposes per NUMA node memory error stats as sysfs entries:

  /sys/devices/system/node/node${X}/memory_failure/pages_poisoned
  /sys/devices/system/node/node${X}/memory_failure/pages_recovered
  /sys/devices/system/node/node${X}/memory_failure/pages_ignored
  /sys/devices/system/node/node${X}/memory_failure/pages_failed
  /sys/devices/system/node/node${X}/memory_failure/pages_delayed

These counters describe how many raw pages are poisoned and after the
attempted recoveries by the kernel, their resolutions: how many are
recovered, ignored, failed, or delayed respectively.

The following math holds for the statistics:
* pages_poisoned = pages_recovered + pages_ignored + pages_failed +
                   pages_delayed
* pages_poisoned * PAGE_SIZE = /proc/meminfo/HardwareCorrupted

Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
---
 drivers/base/node.c    |  3 +++
 include/linux/mm.h     |  5 +++++
 include/linux/mmzone.h | 28 ++++++++++++++++++++++++++++
 mm/memory-failure.c    | 35 +++++++++++++++++++++++++++++++++++
 4 files changed, 71 insertions(+)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index faf3597a96da..b46db17124f3 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -586,6 +586,9 @@ static const struct attribute_group *node_dev_groups[] = {
 	&node_dev_group,
 #ifdef CONFIG_HAVE_ARCH_NODE_DEV_GROUP
 	&arch_node_dev_group,
+#endif
+#ifdef CONFIG_MEMORY_FAILURE
+	&memory_failure_attr_group,
 #endif
 	NULL
 };
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f3f196e4d66d..888576884eb9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3521,6 +3521,11 @@ enum mf_action_page_type {
 	MF_MSG_UNKNOWN,
 };
 
+/*
+ * Sysfs entries for memory failure handling statistics.
+ */
+extern const struct attribute_group memory_failure_attr_group;
+
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
 extern void clear_huge_page(struct page *page,
 			    unsigned long addr_hint,
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index cd28a100d9e4..0a14b35a96da 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1110,6 +1110,31 @@ struct deferred_split {
 };
 #endif
 
+#ifdef CONFIG_MEMORY_FAILURE
+/*
+ * Per NUMA node memory failure handling statistics.
+ */
+struct memory_failure_stats {
+	/*
+	 * Number of pages poisoned.
+	 * Cases not accounted: memory outside kernel control, offline page,
+	 * arch-specific memory_failure (SGX), and hwpoison_filter()
+	 * filtered error events.
+	 */
+	unsigned long pages_poisoned;
+	/*
+	 * Recovery results of poisoned pages handled by memory_failure,
+	 * in sync with mf_result.
+	 * pages_poisoned = pages_ignored + pages_failed +
+	 *		    pages_delayed + pages_recovered
+	 */
+	unsigned long pages_ignored;
+	unsigned long pages_failed;
+	unsigned long pages_delayed;
+	unsigned long pages_recovered;
+};
+#endif
+
 /*
  * On NUMA machines, each NUMA node would have a pg_data_t to describe
  * it's memory layout. On UMA machines there is a single pglist_data which
@@ -1253,6 +1278,9 @@ typedef struct pglist_data {
 #ifdef CONFIG_NUMA
 	struct memory_tier __rcu *memtier;
 #endif
+#ifdef CONFIG_MEMORY_FAILURE
+	struct memory_failure_stats mf_stats;
+#endif
 } pg_data_t;
 
 #define node_present_pages(nid)	(NODE_DATA(nid)->node_present_pages)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index c77a9e37e27e..cb782fa552d5 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -87,6 +87,41 @@ inline void num_poisoned_pages_sub(unsigned long pfn, long i)
 		memblk_nr_poison_sub(pfn, i);
 }
 
+/**
+ * MF_ATTR_RO - Create sysfs entry for each memory failure statistics.
+ * @_name: name of the file in the per NUMA sysfs directory.
+ */
+#define MF_ATTR_RO(_name)					\
+static ssize_t _name##_show(struct device *dev,		\
+			    struct device_attribute *attr,	\
+			    char *buf)				\
+{								\
+	struct memory_failure_stats *mf_stats =			\
+		&NODE_DATA(dev->id)->mf_stats;			\
+	return sprintf(buf, "%lu\n", mf_stats->_name);		\
+}								\
+static DEVICE_ATTR_RO(_name)
+
+MF_ATTR_RO(pages_poisoned);
+MF_ATTR_RO(pages_ignored);
+MF_ATTR_RO(pages_failed);
+MF_ATTR_RO(pages_delayed);
+MF_ATTR_RO(pages_recovered);
+
+static struct attribute *memory_failure_attr[] = {
+	&dev_attr_pages_poisoned.attr,
+	&dev_attr_pages_ignored.attr,
+	&dev_attr_pages_failed.attr,
+	&dev_attr_pages_delayed.attr,
+	&dev_attr_pages_recovered.attr,
+	NULL,
+};
+
+const struct attribute_group memory_failure_attr_group = {
+	.name = "memory_failure",
+	.attrs = memory_failure_attr,
+};
+
 /*
  * Return values:
  *   1:   the page is dissolved (if needed) and taken off from buddy,
-- 
2.39.0.314.g84b9a713c41-goog