Re: [PATCH v8 06/10] tpm: Replace device number bitmap with IDR

[Jarkko Sakkinen]

On Sun, Mar 13, 2016 at 06:54:36PM -0400, Stefan Berger wrote:
> Replace the device number bitmap with IDR. Extend the number of devices we
> can create to 64k.
> Since an IDR allows us to associate a pointer with an ID, we use this now
> to rewrite tpm_chip_find_get() to simply look up the chip pointer by the
> given device ID.
> 
> Protect the IDR calls with a mutex.

I've merged patches up to this to my next branch i.e. you don't have
to carry them in the seres anymore.

/Jarkko

> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> Tested-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> ---
>  drivers/char/tpm/tpm-chip.c      | 84 +++++++++++++++++++++-------------------
>  drivers/char/tpm/tpm-interface.c |  1 +
>  drivers/char/tpm/tpm.h           |  5 +--
>  3 files changed, 48 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 5880377..f62c851 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -29,9 +29,8 @@
>  #include "tpm.h"
>  #include "tpm_eventlog.h"
>  
> -static DECLARE_BITMAP(dev_mask, TPM_NUM_DEVICES);
> -static LIST_HEAD(tpm_chip_list);
> -static DEFINE_SPINLOCK(driver_lock);
> +DEFINE_IDR(dev_nums_idr);
> +static DEFINE_MUTEX(idr_lock);
>  
>  struct class *tpm_class;
>  dev_t tpm_devt;
> @@ -88,20 +87,30 @@ EXPORT_SYMBOL_GPL(tpm_put_ops);
>    */
>  struct tpm_chip *tpm_chip_find_get(int chip_num)
>  {
> -	struct tpm_chip *pos, *chip = NULL;
> +	struct tpm_chip *chip, *res = NULL;
> +	int chip_prev;
> +
> +	mutex_lock(&idr_lock);
> +
> +	if (chip_num == TPM_ANY_NUM) {
> +		chip_num = 0;
> +		do {
> +			chip_prev = chip_num;
> +			chip = idr_get_next(&dev_nums_idr, &chip_num);
> +			if (chip && !tpm_try_get_ops(chip)) {
> +				res = chip;
> +				break;
> +			}
> +		} while (chip_prev != chip_num);
> +	} else {
> +		chip = idr_find_slowpath(&dev_nums_idr, chip_num);
> +		if (chip && !tpm_try_get_ops(chip))
> +			res = chip;
> +	}
>  
> -	rcu_read_lock();
> -	list_for_each_entry_rcu(pos, &tpm_chip_list, list) {
> -		if (chip_num != TPM_ANY_NUM && chip_num != pos->dev_num)
> -			continue;
> +	mutex_unlock(&idr_lock);
>  
> -		/* rcu prevents chip from being free'd */
> -		if (!tpm_try_get_ops(pos))
> -			chip = pos;
> -		break;
> -	}
> -	rcu_read_unlock();
> -	return chip;
> +	return res;
>  }
>  
>  /**
> @@ -114,9 +123,10 @@ static void tpm_dev_release(struct device *dev)
>  {
>  	struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
>  
> -	spin_lock(&driver_lock);
> -	clear_bit(chip->dev_num, dev_mask);
> -	spin_unlock(&driver_lock);
> +	mutex_lock(&idr_lock);
> +	idr_remove(&dev_nums_idr, chip->dev_num);
> +	mutex_unlock(&idr_lock);
> +
>  	kfree(chip);
>  }
>  
> @@ -142,21 +152,18 @@ struct tpm_chip *tpm_chip_alloc(struct device *dev,
>  
>  	mutex_init(&chip->tpm_mutex);
>  	init_rwsem(&chip->ops_sem);
> -	INIT_LIST_HEAD(&chip->list);
>  
>  	chip->ops = ops;
>  
> -	spin_lock(&driver_lock);
> -	chip->dev_num = find_first_zero_bit(dev_mask, TPM_NUM_DEVICES);
> -	spin_unlock(&driver_lock);
> -
> -	if (chip->dev_num >= TPM_NUM_DEVICES) {
> +	mutex_lock(&idr_lock);
> +	rc = idr_alloc(&dev_nums_idr, NULL, 0, TPM_NUM_DEVICES, GFP_KERNEL);
> +	mutex_unlock(&idr_lock);
> +	if (rc < 0) {
>  		dev_err(dev, "No available tpm device numbers\n");
>  		kfree(chip);
> -		return ERR_PTR(-ENOMEM);
> +		return ERR_PTR(rc);
>  	}
> -
> -	set_bit(chip->dev_num, dev_mask);
> +	chip->dev_num = rc;
>  
>  	device_initialize(&chip->dev);
>  
> @@ -242,19 +249,28 @@ static int tpm_add_char_device(struct tpm_chip *chip)
>  		return rc;
>  	}
>  
> +	/* Make the chip available. */
> +	mutex_lock(&idr_lock);
> +	idr_replace(&dev_nums_idr, chip, chip->dev_num);
> +	mutex_unlock(&idr_lock);
> +
>  	return rc;
>  }
>  
>  static void tpm_del_char_device(struct tpm_chip *chip)
>  {
>  	cdev_del(&chip->cdev);
> +	device_del(&chip->dev);
> +
> +	/* Make the chip unavailable. */
> +	mutex_lock(&idr_lock);
> +	idr_replace(&dev_nums_idr, NULL, chip->dev_num);
> +	mutex_unlock(&idr_lock);
>  
>  	/* Make the driver uncallable. */
>  	down_write(&chip->ops_sem);
>  	chip->ops = NULL;
>  	up_write(&chip->ops_sem);
> -
> -	device_del(&chip->dev);
>  }
>  
>  static int tpm1_chip_register(struct tpm_chip *chip)
> @@ -309,11 +325,6 @@ int tpm_chip_register(struct tpm_chip *chip)
>  	if (rc)
>  		goto out_err;
>  
> -	/* Make the chip available. */
> -	spin_lock(&driver_lock);
> -	list_add_tail_rcu(&chip->list, &tpm_chip_list);
> -	spin_unlock(&driver_lock);
> -
>  	chip->flags |= TPM_CHIP_FLAG_REGISTERED;
>  
>  	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
> @@ -350,11 +361,6 @@ void tpm_chip_unregister(struct tpm_chip *chip)
>  	if (!(chip->flags & TPM_CHIP_FLAG_REGISTERED))
>  		return;
>  
> -	spin_lock(&driver_lock);
> -	list_del_rcu(&chip->list);
> -	spin_unlock(&driver_lock);
> -	synchronize_rcu();
> -
>  	if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
>  		sysfs_remove_link(&chip->dev.parent->kobj, "ppi");
>  
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 5caf154..5397b64 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -1139,6 +1139,7 @@ static int __init tpm_init(void)
>  
>  static void __exit tpm_exit(void)
>  {
> +	idr_destroy(&dev_nums_idr);
>  	class_destroy(tpm_class);
>  	unregister_chrdev_region(tpm_devt, TPM_NUM_DEVICES);
>  }
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 5fcf788..928b47f 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -34,7 +34,7 @@
>  enum tpm_const {
>  	TPM_MINOR = 224,	/* officially assigned */
>  	TPM_BUFSIZE = 4096,
> -	TPM_NUM_DEVICES = 256,
> +	TPM_NUM_DEVICES = 65536,
>  	TPM_RETRY = 50,		/* 5 seconds */
>  };
>  
> @@ -195,8 +195,6 @@ struct tpm_chip {
>  	acpi_handle acpi_dev_handle;
>  	char ppi_version[TPM_PPI_VERSION_LEN + 1];
>  #endif /* CONFIG_ACPI */
> -
> -	struct list_head list;
>  };
>  
>  #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
> @@ -492,6 +490,7 @@ static inline void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
>  extern struct class *tpm_class;
>  extern dev_t tpm_devt;
>  extern const struct file_operations tpm_fops;
> +extern struct idr dev_nums_idr;
>  
>  ssize_t	tpm_getcap(struct device *, __be32, cap_t *, const char *);
>  ssize_t tpm_transmit(struct tpm_chip *chip, const char *buf,
> -- 
> 2.4.3
>