path: root/drivers/md/dm-stats.c

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/errno.h>
#include <linux/numa.h>
#include <linux/slab.h>
#include <linux/rculist.h>
#include <linux/threads.h>
#include <linux/preempt.h>
#include <linux/irqflags.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/device-mapper.h>

#include "dm-core.h"
#include "dm-stats.h"

#define DM_MSG_PREFIX "stats"

static int dm_stat_need_rcu_barrier;

/*
 * Using 64-bit values to avoid overflow (which is a
 * problem that block/genhd.c's IO accounting has).
 */
struct dm_stat_percpu {
	unsigned long long sectors[2];
	unsigned long long ios[2];
	unsigned long long merges[2];
	unsigned long long ticks[2];
	unsigned long long io_ticks[2];
	unsigned long long io_ticks_total;
	unsigned long long time_in_queue;
	unsigned long long *histogram;
};

struct dm_stat_shared {
	atomic_t in_flight[2];
	unsigned long long stamp;
	struct dm_stat_percpu tmp;
};

struct dm_stat {
	struct list_head list_entry;
	int id;
	unsigned int stat_flags;
	size_t n_entries;
	sector_t start;
	sector_t end;
	sector_t step;
	unsigned int n_histogram_entries;
	unsigned long long *histogram_boundaries;
	const char *program_id;
	const char *aux_data;
	struct rcu_head rcu_head;
	size_t shared_alloc_size;
	size_t percpu_alloc_size;
	size_t histogram_alloc_size;
	struct dm_stat_percpu *stat_percpu[NR_CPUS];
	struct dm_stat_shared stat_shared[] __counted_by(n_entries);
};

#define STAT_PRECISE_TIMESTAMPS		1

struct dm_stats_last_position {
	sector_t last_sector;
	unsigned int last_rw;
};

#define DM_STAT_MAX_ENTRIES		8388608
#define DM_STAT_MAX_HISTOGRAM_ENTRIES	134217728

/*
 * A typo on the command line could possibly make the kernel run out of memory
 * and crash. To prevent the crash we account all used memory. We fail if we
 * exhaust 1/4 of all memory or 1/2 of vmalloc space.
 */
#define DM_STATS_MEMORY_FACTOR		4
#define DM_STATS_VMALLOC_FACTOR		2

static DEFINE_SPINLOCK(shared_memory_lock);

static unsigned long shared_memory_amount;

static bool __check_shared_memory(size_t alloc_size)
{
	size_t a;

	a = shared_memory_amount + alloc_size;
	if (a < shared_memory_amount)
		return false;
	if (a >> PAGE_SHIFT > totalram_pages() / DM_STATS_MEMORY_FACTOR)
		return false;
#ifdef CONFIG_MMU
	if (a > (VMALLOC_END - VMALLOC_START) / DM_STATS_VMALLOC_FACTOR)
		return false;
#endif
	return true;
}

static bool