path: root/block/genhd.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  gendisk handling
 *
 * Portions Copyright (C) 2020 Christoph Hellwig
 */

#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/log2.h>
#include <linux/pm_runtime.h>
#include <linux/badblocks.h>
#include <linux/part_stat.h>
#include <linux/blktrace_api.h>

#include "blk-throttle.h"
#include "blk.h"
#include "blk-mq-sched.h"
#include "blk-rq-qos.h"
#include "blk-cgroup.h"

static struct kobject *block_depr;

/*
 * Unique, monotonically increasing sequential number associated with block
 * devices instances (i.e. incremented each time a device is attached).
 * Associating uevents with block devices in userspace is difficult and racy:
 * the uevent netlink socket is lossy, and on slow and overloaded systems has
 * a very high latency.
 * Block devices do not have exclusive owners in userspace, any process can set
 * one up (e.g. loop devices). Moreover, device names can be reused (e.g. loop0
 * can be reused again and again).
 * A userspace process setting up a block device and watching for its events
 * cannot thus reliably tell whether an event relates to the device it just set
 * up or another earlier instance with the same name.
 * This sequential number allows userspace processes to solve this problem, and
 * uniquely associate an uevent to the lifetime to a device.
 */
static atomic64_t diskseq;

/* for extended dynamic devt allocation, currently only one major is used */
#define NR_EXT_DEVT		(1 << MINORBITS)
static DEFINE_IDA(ext_devt_ida);

void set_capacity(struct gendisk *disk, sector_t sectors)
{
	struct block_device *bdev = disk->part0;

	spin_lock(&bdev->bd_size_lock);
	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
	bdev->bd_nr_sectors = sectors;
	spin_unlock(&bdev->bd_size_lock);
}
EXPORT_SYMBOL(set_capacity);

/*
 * Set disk capacity and notify if the size is not currently zero and will not
 * be set to zero.  Returns true if a uevent was sent, otherwise false.
 */
bool set_capacity_and_notify(struct gendisk *disk, sector_t size)
{
	sector_t capacity = get_capacity(disk);
	char *envp[] = { "RESIZE=1", NULL };

	set_capacity(disk, size);

	/*
	 * Only print a message and send a uevent if the gendisk is user visible
	 * and alive.  This avoids spamming the log and udev when setting the
	 * initial capacity during probing.
	 */
	if (size == capacity ||
	    !disk_live(disk) ||
	    (disk->flags & GENHD_FL_HIDDEN))
		return false;

	pr_info_ratelimited("%s: detected capacity change from %lld to %lld\n",
		disk->disk_name, capacity, size);

	/*
	 * Historically we did not send a uevent for changes to/from an empty
	 * device.
	 */
	if (!capacity || !size)
		return false;
	kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
	return true;
}
EXPORT_SYMBOL_GPL(set_capacity_and_notify);

static void part_stat_read_all(struct block_device *part,
		struct disk_stats *stat)
{
	int cpu;

	memset(stat, 0, sizeof(struct disk_stats));
	for_each_possible_cpu(cpu) {
		struct disk_stats *ptr = per_cpu_ptr(part->bd_stats, cpu);
		int group;

		for (group = 0; group < NR_STAT_GROUPS; group++) {
			stat->nsecs[group] += ptr->nsecs[group];
			stat->sectors[group] += ptr->sectors[group];
			stat->ios[group] += ptr->ios[group];
			stat->merges[group] += ptr->merges[group];
		}

		stat->io_ticks += ptr->io_ticks;
	}
}

unsigned int part_in_flight(struct block_device *part)
{
	unsigned int inflight = 0;
	int cpu;

	for_each_possible_cpu(cpu) {
		inflight += part_stat_local_read_cpu(part, in_flight[0], cpu) +
			    part_stat_local_read_cpu(part, in_flight[1], cpu);
	}
	if ((int)inflight < 0)
		inflight = 0;

	return inflight;
}

static void part_in_flight_rw(struct block_device *part,
		unsigned int inflight[2])
{
	int cpu;

	inflight[0] = 0;
	inflight[1] = 0;
	for_each_possible_cpu(cpu) {
		inflight[0] += part_stat_local_read_cpu(part, in_flight[0], cpu);
		inflight[1] += part_stat_local_read_cpu(part, in_flight[1], cpu);
	}
	if ((int)inflight[0] < 0)
		inflight[0] = 0;
	if ((int)inflight[1] < 0)
		inflight[1] = 0;
}

/*
 * Can be deleted altogether. Later.
 *
 */
#define BLKDEV_MAJOR_HASH_SIZE 255
static struct blk_major_name {
	struct blk_major_name *next;
	int major;
	char name[16];
#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
	void (*probe)(dev_t devt);
#endif
} *major_names[BLKDEV_MAJOR_HASH_SIZE];
static DEFINE_MUTEX(major_names_lock);
static DEFINE_SPINLOCK(major_names_spinlock);

/* index in the above - for now: assume no multimajor ranges */
static inline int major_to_index(unsigned major)
{
	return major % BLKDEV_MAJOR_HASH_SIZE;
}

#ifdef CONFIG_PROC_FS
void blkdev_show(struct seq_file *seqf, off_t offset)
{
	struct blk_major_name *dp;

	spin_lock(&major_names_spinlock);
	for (dp = major_names[major_to_index(offset)]; dp; dp = dp->next)
		if (dp->major == offset)
			seq_printf(seqf, "%3d %s\n", dp->major, dp->name);
	spin_unlock(&major_names_spinlock);
}
#endif /* CONFIG_PROC_FS */

/**
 * __register_blkdev - register a new block device
 *
 * @major: the requested major device number [1..BLKDEV_MAJOR_MAX-1]. If
 *         @major = 0, try to allocate any unused major number.
 * @name: the name of the new block device as a zero terminated string
 * @probe: pre-devtmpfs / pre-udev callback used to create disks when their
 *	   pre-created device node is accessed. When a probe call uses
 *	   add_disk() and it fails the driver must cleanup resources. This
 *	   interface may soon be removed.
 *
 * The @name must be unique within the system.
 *
 * The return value depends on the @major input parameter:
 *
 *  - if a major device number was requested in range [1..BLKDEV_MAJOR_MAX-1]
 *    then the function returns zero on success, or a negative error code
 *  - if any unused major number was requested with @major = 0 parameter
 *    then the return value is the allocated major number in range
 *    [1..BLKDEV_MAJOR_MAX-1] or a negative error code otherwise
 *
 * See Documentation/admin-guide/devices.txt for the list of allocated
 * major numbers.
 *
 * Use register_blkdev instead for any new code.
 */
int __register_blkdev(unsigned int major, const char *name,
		void (*probe)(dev_t devt))
{
	struct blk_major_name **n, *p;
	int index, ret = 0;

	mutex_lock(&major_names_lock);

	/* temporary */
	if (major == 0) {
		for (index = ARRAY_SIZE(major_names)-1; index > 0; index--) {
			if (major_names[index] == NULL)
				break;
		}

		if (index == 0) {
			printk("%s: failed to get major for %s\n",
			       __func__, name);
			ret = -EBUSY;
			goto out;
		}
		major = index;
		ret = major;
	}

	if (major >= BLKDEV_MAJOR_MAX) {
		pr_err("%s: major requested (%u) is greater than the maximum (%u) for %s\n",
		       __func__, major, BLKDEV_MAJOR_MAX-1, name);

		ret = -EINVAL;
		goto out;
	}

	p = kmalloc(sizeof(struct blk_major_name), GFP_KERNEL);
	if (p == NULL) {
		ret = -ENOMEM;
		goto out;
	}

	p->major = major;
#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
	p->probe = probe;
#endif
	strlcpy(p->name, name, sizeof(p->name));
	p->next = NULL;
	index = major_to_index(major);

	spin_lock(&major_names_spinlock);
	for (n = &major_names[index]; *n; n = &(*n)->next) {
		if ((*n)->major == major)
			break;
	}
	if (!*n)
		*n = p;
	else
		ret = -EBUSY;
	spin_unlock(&major_names_spinlock);

	if (ret < 0) {
		printk("register_blkdev