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dm table: allow upgrade from bio-based to specialized bio-based variant 

In practice this is really only meaningful in the context of the DM
multipath target (which uses dm_table_set_type() to set the type of
device DM should create via its "queue_mode" option).

So this change allows a DM multipath device with "queue_mode bio" to be
upgraded from DM_TYPE_BIO_BASED to DM_TYPE_NVME_BIO_BASED -- iff the
underlying device(s) are NVMe.

DM_TYPE_NVME_BIO_BASED is just a DM core implementation detail that
allows for NVMe-specific optimizations (e.g. use direct_make_request
instead of generic_make_request).  If in the future there is no benefit
or need to distinguish NVMe vs not: then it will be removed.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer 2018-03-05 15:26:06 -05:00
parent 8d47e65948
commit c934edadcc
1 changed files with 5 additions and 9 deletions
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14
drivers/md/dm-table.c
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@ -942,17 +942,12 @@ static int dm_table_determine_type(struct dm_table *t)
if (t->type != DM_TYPE_NONE) {
/* target already set the table's type */
if (t->type == DM_TYPE_BIO_BASED)
return 0;
else if (t->type == DM_TYPE_NVME_BIO_BASED) {
if (!dm_table_does_not_support_partial_completion(t)) {
DMERR("nvme bio-based is only possible with devices"
" that don't support partial completion");
return -EINVAL;
}
/* Fallthru, also verify all devices are blk-mq */
if (t->type == DM_TYPE_BIO_BASED) {
/* possibly upgrade to a variant of bio-based */
goto verify_bio_based;
}
BUG_ON(t->type == DM_TYPE_DAX_BIO_BASED);
BUG_ON(t->type == DM_TYPE_NVME_BIO_BASED);
goto verify_rq_based;
}
@ -985,6 +980,7 @@ static int dm_table_determine_type(struct dm_table *t)
}
if (bio_based) {
verify_bio_based:
/* We must use this table as bio-based */
t->type = DM_TYPE_BIO_BASED;
if (dm_table_supports_dax(t) ||