Re: [RFC PATCH v13 13/20] dm: add finalize hook to target_type

Mike Snitzer
2024-03-02T16:13:13Z

On Wed, Feb 28 2024 at 7:54P -0500,
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
>
> v11:
> + Introduced
>
> v12:
> + No changes
>
> v13:
> + No changes
> ---
> drivers/md/dm.c | 12 ++++++++++++
> include/linux/device-mapper.h | 7 +++++++
> 2 files changed, 19 insertions(+)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 8dcabf84d866..15b46edae49f 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -2266,6 +2266,18 @@ 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 772ab4d74d94..627400b2d9af 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);

This needs some documentation, e.g.: this hook allows DM targets in an
inactive table to complete their setup before the table is made
active.

Mike

>
> void dm_error(const char *message);
>
> @@ -210,6 +216,7 @@ 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;
> --
> 2.43.1
>
>