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authorMike Snitzer <snitzer@redhat.com>2010-08-12 07:14:02 +0400
committerAlasdair G Kergon <agk@redhat.com>2010-08-12 07:14:02 +0400
commit4a0b4ddf261fc89c050fe0a10ec57a61251d7ac0 (patch)
tree23854bb6d42e7cedec9100fcdd63c307ee5d1332 /drivers/md/dm.h
parenta5664dad7e1a278d2915c2bf79cf42250e12d7db (diff)
downloadlinux-4a0b4ddf261fc89c050fe0a10ec57a61251d7ac0.tar.xz
dm: do not initialise full request queue when bio based
Change bio-based mapped devices no longer to have a fully initialized request_queue (request_fn, elevator, etc). This means bio-based DM devices no longer register elevator sysfs attributes ('iosched/' tree or 'scheduler' other than "none"). In contrast, a request-based DM device will continue to have a full request_queue and will register elevator sysfs attributes. Therefore a user can determine a DM device's type by checking if elevator sysfs attributes exist. First allocate a minimalist request_queue structure for a DM device (needed for both bio and request-based DM). Initialization of a full request_queue is deferred until it is known that the DM device is request-based, at the end of the table load sequence. Factor DM device's request_queue initialization: - common to both request-based and bio-based into dm_init_md_queue(). - specific to request-based into dm_init_request_based_queue(). The md->type_lock mutex is used to protect md->queue, in addition to md->type, during table_load(). A DM device's first table_load will establish the immutable md->type. But md->queue initialization, based on md->type, may fail at that time (because blk_init_allocated_queue cannot allocate memory). Therefore any subsequent table_load must (re)try dm_setup_md_queue independently of establishing md->type. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm.h')
-rw-r--r--drivers/md/dm.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 1db782530ce6..450fbd98c48c 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -71,6 +71,8 @@ void dm_unlock_md_type(struct mapped_device *md);
void dm_set_md_type(struct mapped_device *md, unsigned type);
unsigned dm_get_md_type(struct mapped_device *md);
+int dm_setup_md_queue(struct mapped_device *md);
+
/*
* To check the return value from dm_table_find_target().
*/