dm-multipath accepts 0 path mapping.
# echo '0 2097152 multipath 0 0 0 0' | dmsetup create newdev
Such a mapping can be used to release underlying devices while still
holding requests in its queue until working paths come back.
However, once the multipath device is created over blk-mq devices,
it rejects reloading of 0 path mapping:
# echo '0 2097152 multipath 0 0 1 1 queue-length 0 1 1 /dev/sda 1' \
| dmsetup create mpath1
# echo '0 2097152 multipath 0 0 0 0' | dmsetup load mpath1
device-mapper: reload ioctl on mpath1 failed: Invalid argument
Command failed
With following kernel message:
device-mapper: ioctl: can't change device type after initial table load.
DM tries to inherit the current table type using dm_table_set_type()
but it doesn't work as expected because of unnecessary check about
whether the target type is hybrid or not.
Hybrid type is for targets that work as either request-based or bio-based
and not required for blk-mq or non blk-mq checking.
Fixes: 65803c205983 ("dm table: train hybrid target type detection to select blk-mq if appropriate")
Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index d9b00b8..16ba55a 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -820,6 +820,12 @@ void dm_consume_args(struct dm_arg_set *as, unsigned num_args)
}
EXPORT_SYMBOL(dm_consume_args);
+static bool __table_type_request_based(unsigned table_type)
+{
+ return (table_type == DM_TYPE_REQUEST_BASED ||
+ table_type == DM_TYPE_MQ_REQUEST_BASED);
+}
+
static int dm_table_set_type(struct dm_table *t)
{
unsigned i;
@@ -852,8 +858,7 @@ static int dm_table_set_type(struct dm_table *t)
* Determine the type from the live device.
* Default to bio-based if device is new.
*/
- if (live_md_type == DM_TYPE_REQUEST_BASED ||
- live_md_type == DM_TYPE_MQ_REQUEST_BASED)
+ if (__table_type_request_based(live_md_type))
request_based = 1;
else
bio_based = 1;
@@ -903,7 +908,7 @@ static int dm_table_set_type(struct dm_table *t)
}
t->type = DM_TYPE_MQ_REQUEST_BASED;
- } else if (hybrid && list_empty(devices) && live_md_type != DM_TYPE_NONE) {
+ } else if (list_empty(devices) && __table_type_request_based(live_md_type)) {
/* inherit live MD type */
t->type = live_md_type;
@@ -925,10 +930,7 @@ struct target_type *dm_table_get_immutable_target_type(struct dm_table *t)
bool dm_table_request_based(struct dm_table *t)
{
- unsigned table_type = dm_table_get_type(t);
-
- return (table_type == DM_TYPE_REQUEST_BASED ||
- table_type == DM_TYPE_MQ_REQUEST_BASED);
+ return __table_type_request_based(dm_table_get_type(t));
}
bool dm_table_mq_request_based(struct dm_table *t)
--
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