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Commit 7d76345d authored by Kiyoshi Ueda's avatar Kiyoshi Ueda Committed by Alasdair G Kergon
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dm request: extend target interface 



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 managing the block layer queue.
              But in request-based dm, dm core has to do that
              since dm core manages the block layer queue.

Signed-off-by: default avatarKiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 8fbf26ad

include/linux/device-mapper.h

+15 −0
Original line number Diff line number Diff line
@@ -45,6 +45,8 @@ typedef void (*dm_dtr_fn) (struct dm_target *ti); 
 */

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:
@@ -57,6 +59,9 @@ typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio, 
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);
@@ -75,6 +80,13 @@ typedef int (*dm_ioctl_fn) (struct dm_target *ti, unsigned int cmd, 
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);



/*
@@ -107,7 +119,9 @@ 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;
@@ -117,6 +131,7 @@ struct target_type { 
	dm_message_fn message;

	dm_ioctl_fn ioctl;

	dm_merge_fn merge;

	dm_busy_fn busy;

};



struct io_restrictions {