On Wed, 21 Aug 2013, Joe Jin wrote:
> commit a5664da "dm ioctl: make bio or request based device type immutable"
> prevented "dmsetup wape_table" change the target type to "error".
That commit a5664da is there for a reason (it is not possible to change
bio-based device to request-based and vice versa) and I don't really see
how this patch is supposed to work.
If there are bios that are in flight and that already passed through
blk_queue_bio, and you change the device from request-based to bio-based,
what are you going to do with them? - The patch doesn't do anything about
it.
A better approach would be to create a new request-based target "error-rq"
and change the multipath target to "error-rq" target. That way, you don't
have to change device type from request based to bio based.
Mikulas
> -v2: setup md->queue even target type is "error".
>
> Signed-off-by: Joe Jin <joe.jin@xxxxxxxxxx>
> ---
> drivers/md/dm-ioctl.c | 4 ++++
> drivers/md/dm-table.c | 12 ++++++++++++
> drivers/md/dm.h | 1 +
> 3 files changed, 17 insertions(+)
>
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index f1b7586..2a9b63d 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -1280,6 +1280,9 @@ static int table_load(struct dm_ioctl *param, size_t param_size)
> goto out;
> }
>
> + if (dm_is_error_target(t))
> + goto error_target;
> +
> /* Protect md->type and md->queue against concurrent table loads. */
> dm_lock_md_type(md);
> if (dm_get_md_type(md) == DM_TYPE_NONE)
> @@ -1293,6 +1296,7 @@ static int table_load(struct dm_ioctl *param, size_t param_size)
> goto out;
> }
>
> +error_target:
> /* setup md->queue to reflect md's type (may block) */
> r = dm_setup_md_queue(md);
> if (r) {
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index f221812..27be46a 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -184,6 +184,18 @@ static int alloc_targets(struct dm_table *t, unsigned int num)
> return 0;
> }
>
> +bool dm_is_error_target(struct dm_table *t)
> +{
> + unsigned i;
> +
> + for (i = 0; i < t->num_targets; i++) {
> + struct dm_target *tgt = t->targets + i;
> + if (strcmp(tgt->type->name, "error") == 0)
> + return true;
> + }
> + return false;
> +}
> +
> int dm_table_create(struct dm_table **result, fmode_t mode,
> unsigned num_targets, struct mapped_device *md)
> {
> diff --git a/drivers/md/dm.h b/drivers/md/dm.h
> index 45b97da..c7bceeb 100644
> --- a/drivers/md/dm.h
> +++ b/drivers/md/dm.h
> @@ -69,6 +69,7 @@ unsigned dm_table_get_type(struct dm_table *t);
> struct target_type *dm_table_get_immutable_target_type(struct dm_table *t);
> bool dm_table_request_based(struct dm_table *t);
> bool dm_table_supports_discards(struct dm_table *t);
> +bool dm_is_error_target(struct dm_table *t);
> int dm_table_alloc_md_mempools(struct dm_table *t);
> void dm_table_free_md_mempools(struct dm_table *t);
> struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
> --
> 1.8.3.1
>
> --
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