block/holder.c

Source file repositories/reference/linux-study-clean/block/holder.c

File Facts

System
Linux kernel
Corpus path
block/holder.c
Extension
.c
Size
3921 bytes
Lines
157
Domain
Representative Device Path
Bucket
PCIe NVMe Storage Path
Inferred role
Representative Device Path: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Part of the selected hardware vertical slice: PCI discovery, driver binding, NVMe queues, block requests, DMA, interrupts, and completion.

Dependency Surface

Detected Declarations

Annotated Snippet

struct bd_holder_disk {
	struct list_head	list;
	struct kobject		*holder_dir;
	int			refcnt;
};

static DEFINE_MUTEX(blk_holder_mutex);

static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
						  struct gendisk *disk)
{
	struct bd_holder_disk *holder;

	list_for_each_entry(holder, &disk->slave_bdevs, list)
		if (holder->holder_dir == bdev->bd_holder_dir)
			return holder;
	return NULL;
}

static int add_symlink(struct kobject *from, struct kobject *to)
{
	return sysfs_create_link(from, to, kobject_name(to));
}

static void del_symlink(struct kobject *from, struct kobject *to)
{
	sysfs_remove_link(from, kobject_name(to));
}

/**
 * bd_link_disk_holder - create symlinks between holding disk and slave bdev
 * @bdev: the claimed slave bdev
 * @disk: the holding disk
 *
 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
 *
 * This functions creates the following sysfs symlinks.
 *
 * - from "slaves" directory of the holder @disk to the claimed @bdev
 * - from "holders" directory of the @bdev to the holder @disk
 *
 * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
 * passed to bd_link_disk_holder(), then:
 *
 *   /sys/block/dm-0/slaves/sda --> /sys/block/sda
 *   /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
 *
 * The caller must have claimed @bdev before calling this function and
 * ensure that both @bdev and @disk are valid during the creation and
 * lifetime of these symlinks.
 *
 * CONTEXT:
 * Might sleep.
 *
 * RETURNS:
 * 0 on success, -errno on failure.
 */
int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
{
	struct bd_holder_disk *holder;
	int ret = 0;

	if (WARN_ON_ONCE(!disk->slave_dir))
		return -EINVAL;

	if (bdev->bd_disk == disk)
		return -EINVAL;

	/*
	 * del_gendisk drops the initial reference to bd_holder_dir, so we
	 * need to keep our own here to allow for cleanup past that point.
	 */
	mutex_lock(&bdev->bd_disk->open_mutex);
	if (!disk_live(bdev->bd_disk)) {
		mutex_unlock(&bdev->bd_disk->open_mutex);
		return -ENODEV;
	}
	kobject_get(bdev->bd_holder_dir);
	mutex_unlock(&bdev->bd_disk->open_mutex);

	mutex_lock(&blk_holder_mutex);
	WARN_ON_ONCE(!bdev->bd_holder);

	holder = bd_find_holder_disk(bdev, disk);
	if (holder) {
		kobject_put(bdev->bd_holder_dir);
		holder->refcnt++;
		goto out_unlock;
	}

Annotation

Implementation Notes