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Date:   Mon, 23 Oct 2023 23:52:30 -0400
Message-ID: <2121d9724f32ea5926574f9aba806b69.paul@paul-moore.com>
From:   Paul Moore <paul@paul-moore.com>
To:     Fan Wu <wufan@linux.microsoft.com>, corbet@lwn.net,
        zohar@linux.ibm.com, jmorris@namei.org, serge@hallyn.com,
        tytso@mit.edu, ebiggers@kernel.org, axboe@kernel.dk,
        agk@redhat.com, snitzer@kernel.org, eparis@redhat.com
Cc:     linux-doc@vger.kernel.org, linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-fscrypt@vger.kernel.org, linux-block@vger.kernel.org,
        dm-devel@redhat.com, audit@vger.kernel.org,
        roberto.sassu@huawei.com, linux-kernel@vger.kernel.org,
        Fan Wu <wufan@linux.microsoft.com>
Subject: Re: [PATCH RFC v11 12/19] dm: add finalize hook to target_type
References: <1696457386-3010-13-git-send-email-wufan@linux.microsoft.com>
In-Reply-To: <1696457386-3010-13-git-send-email-wufan@linux.microsoft.com>
Precedence: bulk

On Oct  4, 2023 Fan Wu <wufan@linux.microsoft.com> wrote:
> 
> This patch adds a target finalize hook.
> 
> The hook is triggered just before activating an inactive table of a
> mapped device. If it returns an error the __bind get cancelled.
> 
> The dm-verity target will use this hook to attach the dm-verity's
> roothash metadata to the block_device struct of the mapped device.
> 
> Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
> ---
> v1-v10:
>   + Not present
> ---
>  drivers/md/dm.c               | 12 ++++++++++++
>  include/linux/device-mapper.h |  7 +++++++
>  2 files changed, 19 insertions(+)

We need an ACK and confirmation from Alasdair and/or Mike that this
is the right approach.

> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 64a1f306c96c..3be9cc35306d 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -2239,6 +2239,18 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
>  		goto out;
>  	}
>  
> +	for (unsigned int i = 0; i < t->num_targets; i++) {
> +		struct dm_target *ti = dm_table_get_target(t, i);
> +
> +		if (ti->type->finalize) {
> +			ret = ti->type->finalize(ti);
> +			if (ret) {
> +				old_map = ERR_PTR(ret);
> +				goto out;
> +			}
> +		}
> +	}
> +
>  	old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
>  	rcu_assign_pointer(md->map, (void *)t);
>  	md->immutable_target_type = dm_table_get_immutable_target_type(t);
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 69d0435c7ebb..4040e84a8ec7 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -160,6 +160,12 @@ typedef int (*dm_dax_zero_page_range_fn)(struct dm_target *ti, pgoff_t pgoff,
>   */
>  typedef size_t (*dm_dax_recovery_write_fn)(struct dm_target *ti, pgoff_t pgoff,
>  		void *addr, size_t bytes, struct iov_iter *i);
> +/*
> + * Returns:
> + *  < 0 : error
> + *  = 0 : success
> + */
> +typedef int (*dm_finalize_fn) (struct dm_target *target);
>  
>  void dm_error(const char *message);
>  
> @@ -209,6 +215,7 @@ struct target_type {
>  	dm_dax_direct_access_fn direct_access;
>  	dm_dax_zero_page_range_fn dax_zero_page_range;
>  	dm_dax_recovery_write_fn dax_recovery_write;
> +	dm_finalize_fn finalize;
>  
>  	/* For internal device-mapper use. */
>  	struct list_head list;
> -- 
> 2.25.1

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