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author | Kiyoshi Ueda <k-ueda@ct.jp.nec.com> | 2009-06-22 10:12:36 +0100 |
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committer | Alasdair G Kergon <agk@redhat.com> | 2009-06-22 10:12:36 +0100 |
commit | e6ee8c0b767540f59e20da3ced282601db8aa502 (patch) | |
tree | 101cb830994734eb45a4a47cd5988f24da67fa4f /drivers/md/dm.h | |
parent | cec47e3d4a861e1d942b3a580d0bbef2700d2bb2 (diff) | |
download | op-kernel-dev-e6ee8c0b767540f59e20da3ced282601db8aa502.zip op-kernel-dev-e6ee8c0b767540f59e20da3ced282601db8aa502.tar.gz |
dm: enable request based option
This patch enables request-based dm.
o Request-based dm and bio-based dm coexist, since there are
some target drivers which are more fitting to bio-based dm.
Also, there are other bio-based devices in the kernel
(e.g. md, loop).
Since bio-based device can't receive struct request,
there are some limitations on device stacking between
bio-based and request-based.
type of underlying device
bio-based request-based
----------------------------------------------
bio-based OK OK
request-based -- OK
The device type is recognized by the queue flag in the kernel,
so dm follows that.
o The type of a dm device is decided at the first table binding time.
Once the type of a dm device is decided, the type can't be changed.
o Mempool allocations are deferred to at the table loading time, since
mempools for request-based dm are different from those for bio-based
dm and needed mempool type is fixed by the type of table.
o Currently, request-based dm supports only tables that have a single
target. To support multiple targets, we need to support request
splitting or prevent bio/request from spanning multiple targets.
The former needs lots of changes in the block layer, and the latter
needs that all target drivers support merge() function.
Both will take a time.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.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.h | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/drivers/md/dm.h b/drivers/md/dm.h index 8dcabb1..a7663eb 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -23,6 +23,13 @@ #define DM_SUSPEND_NOFLUSH_FLAG (1 << 1) /* + * Type of table and mapped_device's mempool + */ +#define DM_TYPE_NONE 0 +#define DM_TYPE_BIO_BASED 1 +#define DM_TYPE_REQUEST_BASED 2 + +/* * List of devices that a metadevice uses and should open/close. */ struct dm_dev_internal { @@ -32,6 +39,7 @@ struct dm_dev_internal { }; struct dm_table; +struct dm_md_mempools; /*----------------------------------------------------------------- * Internal table functions. @@ -51,12 +59,23 @@ void dm_table_postsuspend_targets(struct dm_table *t); int dm_table_resume_targets(struct dm_table *t); int dm_table_any_congested(struct dm_table *t, int bdi_bits); int dm_table_any_busy_target(struct dm_table *t); +int dm_table_set_type(struct dm_table *t); +unsigned dm_table_get_type(struct dm_table *t); +bool dm_table_request_based(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); /* * To check the return value from dm_table_find_target(). */ #define dm_target_is_valid(t) ((t)->table) +/* + * To check whether the target type is request-based or not (bio-based). + */ +#define dm_target_request_based(t) ((t)->type->map_rq != NULL) + /*----------------------------------------------------------------- * A registry of target types. *---------------------------------------------------------------*/ @@ -102,4 +121,10 @@ void dm_kobject_uevent(struct mapped_device *md, enum kobject_action action, int dm_kcopyd_init(void); void dm_kcopyd_exit(void); +/* + * Mempool operations + */ +struct dm_md_mempools *dm_alloc_md_mempools(unsigned type); +void dm_free_md_mempools(struct dm_md_mempools *pools); + #endif |