Re: [PATCH 2/2] dm: call PR reserve/unreserve on each underlying device

[Mike Christie <mchristi@redhat.com>]

On 07/08/2016 07:23 AM, Christoph Hellwig wrote:
> So far we tried to rely on the SCSI 'all target ports' bit to register
> all path, but for many setups this didn't work properly as the different
> path aren seen as separate initiators to the target instead of multiple
> ports of the same initiator.  Because of that we'll stop setting the
> 'all target ports' bit in SCSI, and let device mapper handle iterating
> over the device for each path and register it manually.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/md/dm.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 70 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 1b2f962..e4e98b7 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -3601,26 +3601,81 @@ void dm_free_md_mempools(struct dm_md_mempools *pools)
>  	kfree(pools);
>  }
>  
> -static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
> -			  u32 flags)
> +struct dm_pr {
> +	u64	old_key;
> +	u64	new_key;
> +	u32	flags;
> +	bool	fail_early;
> +};
> +
> +static int dm_call_pr(struct block_device *bdev, iterate_devices_callout_fn fn,
> +		void *data)
>  {
>  	struct mapped_device *md = bdev->bd_disk->private_data;
> -	const struct pr_ops *ops;
> -	fmode_t mode;
> -	int r;
> +	struct dm_table *table;
> +	struct dm_target *ti;
> +	int ret = 0, srcu_idx;
>  
> -	r = dm_grab_bdev_for_ioctl(md, &bdev, &mode);
> -	if (r < 0)
> -		return r;
> +	table = dm_get_live_table(md, &srcu_idx);
> +	if (!table || !dm_table_get_size(table))
> +		return -ENOTTY;
>  
> -	ops = bdev->bd_disk->fops->pr_ops;
> -	if (ops && ops->pr_register)
> -		r = ops->pr_register(bdev, old_key, new_key, flags);
> -	else
> -		r = -EOPNOTSUPP;
> +	/* We only support devices that have a single target */
> +	ret = -ENOTTY;
> +	if (dm_table_get_num_targets(table) != 1)
> +		goto out;
> +	ti = dm_table_get_target(table, 0);
>  
> -	bdput(bdev);
> -	return r;
> +	ret = -EINVAL;
> +	if (!ti->type->iterate_devices)
> +		goto out;
> +
> +	ret = ti->type->iterate_devices(ti, fn, data);
> +	if (ret)
> +		goto out;
> +
> +	ret = 0;
> +out:
> +	dm_put_live_table(md, srcu_idx);
> +	return ret;
> +}
> +
> +/*
> + * For register / unregister we need to manually call out to every path.
> + */
> +static int __dm_pr_register(struct dm_target *ti, struct dm_dev *dev,
> +		sector_t start, sector_t len, void *data)
> +{
> +	struct dm_pr *pr = data;
> +	const struct pr_ops *ops = dev->bdev->bd_disk->fops->pr_ops;
> +
> +	if (!ops || !ops->pr_register)
> +		return -EOPNOTSUPP;
> +	return ops->pr_register(dev->bdev, pr->old_key, pr->new_key, pr->flags);
> +}
> +
> +static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
> +			  u32 flags)
> +{
> +	struct dm_pr pr = {
> +		.old_key	= old_key,
> +		.new_key	= new_key,
> +		.flags		= flags,
> +		.fail_early	= true,
> +	};
> +	int ret;
> +
> +	ret = dm_call_pr(bdev, __dm_pr_register, &pr);
> +	if (ret && new_key) {
> +		/* unregister all paths if we failed to register any path */
> +		pr.old_key = new_key;
> +		pr.new_key = 0;
> +		pr.flags = 0;
> +		pr.fail_early = false;
> +		dm_call_pr(bdev, __dm_pr_register, &pr);
> +	}
> +
> +	return ret;
>  }
>  
>  static int dm_pr_reserve(struct block_device *bdev, u64 key, enum pr_type type,
> 



Reviewed-by: Mike Christie <mchristi@redhat.com>