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dm mpath: add optional "queue_mode" feature

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Allow a user to specify an optional feature 'queue_mode <mode>' where
<mode> may be "bio", "rq" or "mq" -- which corresponds to bio-based,
request_fn rq-based, and blk-mq rq-based respectively.

If the queue_mode feature isn't specified the default for the
"multipath" target is still "rq" but if dm_mod.use_blk_mq is set to Y
it'll default to mode "mq".

This new queue_mode feature introduces the ability for each multipath
device to have its own queue_mode (whereas before this feature all
multipath devices effectively had to have the same queue_mode).

This commit also goes a long way to eliminate the awkward (ab)use of
DM_TYPE_*, the associated filter_md_type() and other relatively fragile
and difficult to maintain code.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer
2016-05-24 21:16:51 -04:00
parent bf661be1fc
commit e83068a5fa
7 changed files with 159 additions and 119 deletions
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15
drivers/md/dm.c
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@@ -1738,23 +1738,14 @@ struct queue_limits *dm_get_queue_limits(struct mapped_device *md)
}
EXPORT_SYMBOL_GPL(dm_get_queue_limits);
static unsigned filter_md_type(unsigned type, struct mapped_device *md)
{
if (type == DM_TYPE_BIO_BASED)
return type;
return !md->use_blk_mq ? DM_TYPE_REQUEST_BASED : DM_TYPE_MQ_REQUEST_BASED;
}
/*
* Setup the DM device's queue based on md's type
*/
int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
{
int r;
unsigned md_type = filter_md_type(dm_get_md_type(md), md);
switch (md_type) {
switch (dm_get_md_type(md)) {
case DM_TYPE_REQUEST_BASED:
r = dm_old_init_request_queue(md);
if (r) {
@@ -1763,7 +1754,7 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
}
break;
case DM_TYPE_MQ_REQUEST_BASED:
r = dm_mq_init_request_queue(md, dm_table_get_immutable_target(t));
r = dm_mq_init_request_queue(md, t);
if (r) {
DMERR("Cannot initialize queue for request-based dm-mq mapped device");
return r;
@@ -2472,8 +2463,6 @@ struct dm_md_mempools *dm_alloc_md_mempools(struct mapped_device *md, unsigned t
if (!pools)
return NULL;
type = filter_md_type(type, md);
switch (type) {
case DM_TYPE_BIO_BASED:
cachep = _io_cache;