block_dev.c

ARM 嵌入式 系统 设计与实例开发 实验教材 二源码

				return new_bdev;
			}
			spin_unlock(&bdev_lock);
			iput(new_bdev->bd_inode);
		}
		destroy_bdev(new_bdev);
	}
	return bdev;
}

static inline void __bd_forget(struct inode *inode)
{
	list_del_init(&inode->i_devices);
	inode->i_bdev = NULL;
	inode->i_mapping = &inode->i_data;
}

void bdput(struct block_device *bdev)
{
	if (atomic_dec_and_lock(&bdev->bd_count, &bdev_lock)) {
		struct list_head *p;
		if (bdev->bd_openers)
			BUG();
		list_del(&bdev->bd_hash);
		while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
			__bd_forget(list_entry(p, struct inode, i_devices));
		}
		spin_unlock(&bdev_lock);
		iput(bdev->bd_inode);
		destroy_bdev(bdev);
	}
}
 
int bd_acquire(struct inode *inode)
{
	struct block_device *bdev;
	spin_lock(&bdev_lock);
	if (inode->i_bdev) {
		atomic_inc(&inode->i_bdev->bd_count);
		spin_unlock(&bdev_lock);
		return 0;
	}
	spin_unlock(&bdev_lock);
	bdev = bdget(kdev_t_to_nr(inode->i_rdev));
	if (!bdev)
		return -ENOMEM;
	spin_lock(&bdev_lock);
	if (!inode->i_bdev) {
		inode->i_bdev = bdev;
		inode->i_mapping = bdev->bd_inode->i_mapping;
		list_add(&inode->i_devices, &bdev->bd_inodes);
	} else if (inode->i_bdev != bdev)
		BUG();
	spin_unlock(&bdev_lock);
	return 0;
}

/* Call when you free inode */

void bd_forget(struct inode *inode)
{
	spin_lock(&bdev_lock);
	if (inode->i_bdev)
		__bd_forget(inode);
	spin_unlock(&bdev_lock);
}

static struct {
	const char *name;
	struct block_device_operations *bdops;
} blkdevs[MAX_BLKDEV];

int get_blkdev_list(char * p)
{
	int i;
	int len;

	len = sprintf(p, "\nBlock devices:\n");
	for (i = 0; i < MAX_BLKDEV ; i++) {
		if (blkdevs[i].bdops) {
			len += sprintf(p+len, "%3d %s\n", i, blkdevs[i].name);
		}
	}
	return len;
}

/*
	Return the function table of a device.
	Load the driver if needed.
*/
const struct block_device_operations * get_blkfops(unsigned int major)
{
	const struct block_device_operations *ret = NULL;

	/* major 0 is used for non-device mounts */
	if (major && major < MAX_BLKDEV) {
#ifdef CONFIG_KMOD
		if (!blkdevs[major].bdops) {
			char name[20];
			sprintf(name, "block-major-%d", major);
			request_module(name);
		}
#endif
		ret = blkdevs[major].bdops;
	}
	return ret;
}

int register_blkdev(unsigned int major, const char * name, struct block_device_operations *bdops)
{
	if (major == 0) {
		for (major = MAX_BLKDEV-1; major > 0; major--) {
			if (blkdevs[major].bdops == NULL) {
				blkdevs[major].name = name;
				blkdevs[major].bdops = bdops;
				return major;
			}
		}
		return -EBUSY;
	}
	if (major >= MAX_BLKDEV)
		return -EINVAL;
	if (blkdevs[major].bdops && blkdevs[major].bdops != bdops)
		return -EBUSY;
	blkdevs[major].name = name;
	blkdevs[major].bdops = bdops;
	return 0;
}

int unregister_blkdev(unsigned int major, const char * name)
{
	if (major >= MAX_BLKDEV)
		return -EINVAL;
	if (!blkdevs[major].bdops)
		return -EINVAL;
	if (strcmp(blkdevs[major].name, name))
		return -EINVAL;
	blkdevs[major].name = NULL;
	blkdevs[major].bdops = NULL;
	return 0;
}

/*
 * This routine checks whether a removable media has been changed,
 * and invalidates all buffer-cache-entries in that case. This
 * is a relatively slow routine, so we have to try to minimize using
 * it. Thus it is called only upon a 'mount' or 'open'. This
 * is the best way of combining speed and utility, I think.
 * People changing diskettes in the middle of an operation deserve
 * to lose :-)
 */
int check_disk_change(kdev_t dev)
{
	int i;
	const struct block_device_operations * bdops = NULL;

	i = MAJOR(dev);
	if (i < MAX_BLKDEV)
		bdops = blkdevs[i].bdops;
	if (bdops == NULL) {
		devfs_handle_t de;

		de = devfs_find_handle (NULL, NULL, i, MINOR (dev),
					DEVFS_SPECIAL_BLK, 0);
		if (de) {
			bdops = devfs_get_ops (de);
			devfs_put_ops (de); /* We're running in owner module */
		}
	}
	if (bdops == NULL)
		return 0;
	if (bdops->check_media_change == NULL)
		return 0;
	if (!bdops->check_media_change(dev))
		return 0;

	printk(KERN_DEBUG "VFS: Disk change detected on device %s\n",
		bdevname(dev));

	if (invalidate_device(dev, 0))
		printk("VFS: busy inodes on changed media.\n");

	if (bdops->revalidate)
		bdops->revalidate(dev);
	return 1;
}

int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)
{
	int res;
	mm_segment_t old_fs = get_fs();

	if (!bdev->bd_op->ioctl)
		return -EINVAL;
	set_fs(KERNEL_DS);
	res = bdev->bd_op->ioctl(bdev->bd_inode, NULL, cmd, arg);
	set_fs(old_fs);
	return res;
}

static int do_open(struct block_device *bdev, struct inode *inode, struct file *file)
{
	int ret = -ENXIO;
	kdev_t dev = to_kdev_t(bdev->bd_dev);

	down(&bdev->bd_sem);
	lock_kernel();
	if (!bdev->bd_op)
		bdev->bd_op = get_blkfops(MAJOR(dev));
	if (bdev->bd_op) {
		ret = 0;
		if (bdev->bd_op->owner)
			__MOD_INC_USE_COUNT(bdev->bd_op->owner);
		if (bdev->bd_op->open)
			ret = bdev->bd_op->open(inode, file);
		if (!ret) {
			bdev->bd_openers++;
			bdev->bd_inode->i_size = blkdev_size(dev);
			bdev->bd_inode->i_blkbits = blksize_bits(block_size(dev));
		} else {
			if (bdev->bd_op->owner)
				__MOD_DEC_USE_COUNT(bdev->bd_op->owner);
			if (!bdev->bd_openers)
				bdev->bd_op = NULL;
		}
	}
	unlock_kernel();
	up(&bdev->bd_sem);
	if (ret)
		bdput(bdev);
	return ret;
}

int blkdev_get(struct block_device *bdev, mode_t mode, unsigned flags, int kind)
{
	/*
	 * This crockload is due to bad choice of ->open() type.
	 * It will go away.
	 * For now, block device ->open() routine must _not_
	 * examine anything in 'inode' argument except ->i_rdev.
	 */
	struct file fake_file = {};
	struct dentry fake_dentry = {};
	fake_file.f_mode = mode;
	fake_file.f_flags = flags;
	fake_file.f_dentry = &fake_dentry;
	fake_dentry.d_inode = bdev->bd_inode;

	return do_open(bdev, bdev->bd_inode, &fake_file);
}

int blkdev_open(struct inode * inode, struct file * filp)
{
	struct block_device *bdev;

	/*
	 * Preserve backwards compatibility and allow large file access
	 * even if userspace doesn't ask for it explicitly. Some mkfs
	 * binary needs it. We might want to drop this workaround
	 * during an unstable branch.
	 */
	filp->f_flags |= O_LARGEFILE;

	bd_acquire(inode);
	bdev = inode->i_bdev;

	return do_open(bdev, inode, filp);
}	

int blkdev_put(struct block_device *bdev, int kind)
{
	int ret = 0;
	kdev_t rdev = to_kdev_t(bdev->bd_dev); /* this should become bdev */
	struct inode *bd_inode = bdev->bd_inode;

	down(&bdev->bd_sem);
	lock_kernel();
	if (kind == BDEV_FILE)
		__block_fsync(bd_inode);
	else if (kind == BDEV_FS)
		fsync_no_super(rdev);
	if (!--bdev->bd_openers)
		kill_bdev(bdev);
	if (bdev->bd_op->release)
		ret = bdev->bd_op->release(bd_inode, NULL);
	if (bdev->bd_op->owner)
		__MOD_DEC_USE_COUNT(bdev->bd_op->owner);
	if (!bdev->bd_openers)
		bdev->bd_op = NULL;
	unlock_kernel();
	up(&bdev->bd_sem);
	bdput(bdev);
	return ret;
}

int blkdev_close(struct inode * inode, struct file * filp)
{
	return blkdev_put(inode->i_bdev, BDEV_FILE);
}

static int blkdev_ioctl(struct inode *inode, struct file *file, unsigned cmd,
			unsigned long arg)
{
	if (inode->i_bdev->bd_op->ioctl)
		return inode->i_bdev->bd_op->ioctl(inode, file, cmd, arg);
	return -EINVAL;
}

struct address_space_operations def_blk_aops = {
	readpage: blkdev_readpage,
	writepage: blkdev_writepage,
	sync_page: block_sync_page,
	prepare_write: blkdev_prepare_write,
	commit_write: blkdev_commit_write,
	direct_IO: blkdev_direct_IO,
};

struct file_operations def_blk_fops = {
	open:		blkdev_open,
	release:	blkdev_close,
	llseek:		block_llseek,
	read:		generic_file_read,
	write:		generic_file_write,
	mmap:		generic_file_mmap,
	fsync:		block_fsync,
	ioctl:		blkdev_ioctl,
};

const char * bdevname(kdev_t dev)
{
	static char buffer[32];
	const char * name = blkdevs[MAJOR(dev)].name;

	if (!name)
		name = "unknown-block";

	sprintf(buffer, "%s(%d,%d)", name, MAJOR(dev), MINOR(dev));
	return buffer;
}