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Go Back   Linux Archive > Redhat > Device-mapper Development

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Old 09-12-2008, 02:45 PM
Kiyoshi Ueda
Default dm: add target interfaces for request-based dm

This patch adds the following target interfaces for request-based dm.

map_rq : for mapping a request

rq_end_io : for finishing a request

busy : for avoiding performance regression from bio-based dm.
Target can tell dm core not to map requests now, and
that may help requests in the block layer queue to be
bigger by I/O merging.
In bio-based dm, this behavior is done by device
drivers which managing the block layer queue.
But in request-based dm, dm core has to do that
since dm core manages the block layer queue, and
target drivers help is needed for it.

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Alasdair G Kergon <agk@redhat.com>
include/linux/device-mapper.h | 15 +++++++++++++++
1 files changed, 15 insertions(+)

Index: 2.6.27-rc6/include/linux/device-mapper.h
================================================== =================
--- 2.6.27-rc6.orig/include/linux/device-mapper.h
+++ 2.6.27-rc6/include/linux/device-mapper.h
@@ -46,6 +46,8 @@ typedef void (*dm_dtr_fn) (struct dm_tar
typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio,
union map_info *map_context);
+typedef int (*dm_map_request_fn) (struct dm_target *ti, struct request *clone,
+ union map_info *map_context);

* Returns:
@@ -58,6 +60,9 @@ typedef int (*dm_map_fn) (struct dm_targ
typedef int (*dm_endio_fn) (struct dm_target *ti,
struct bio *bio, int error,
union map_info *map_context);
+typedef int (*dm_request_endio_fn) (struct dm_target *ti,
+ struct request *clone, int error,
+ union map_info *map_context);

typedef void (*dm_flush_fn) (struct dm_target *ti);
typedef void (*dm_presuspend_fn) (struct dm_target *ti);
@@ -77,6 +82,13 @@ typedef int (*dm_ioctl_fn) (struct dm_ta
typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
struct bio_vec *biovec, int max_size);

+ * Returns:
+ * 0: The target can handle the next I/O immediately.
+ * 1: The target can't handle the next I/O immediately.
+ */
+typedef int (*dm_busy_fn) (struct dm_target *ti);
void dm_error(const char *message);

@@ -103,7 +115,9 @@ struct target_type {
dm_ctr_fn ctr;
dm_dtr_fn dtr;
dm_map_fn map;
+ dm_map_request_fn map_rq;
dm_endio_fn end_io;
+ dm_request_endio_fn rq_end_io;
dm_flush_fn flush;
dm_presuspend_fn presuspend;
dm_postsuspend_fn postsuspend;
@@ -113,6 +127,7 @@ struct target_type {
dm_message_fn message;
dm_ioctl_fn ioctl;
dm_merge_fn merge;
+ dm_busy_fn busy;

struct io_restrictions {

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