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: 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>
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@ -45,6 +45,8 @@ typedef void (*dm_dtr_fn) (struct dm_target *ti);
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*/
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typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio,
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union map_info *map_context);
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typedef int (*dm_map_request_fn) (struct dm_target *ti, struct request *clone,
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union map_info *map_context);
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/*
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* Returns:
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@ -57,6 +59,9 @@ typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio,
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typedef int (*dm_endio_fn) (struct dm_target *ti,
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struct bio *bio, int error,
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union map_info *map_context);
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typedef int (*dm_request_endio_fn) (struct dm_target *ti,
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struct request *clone, int error,
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union map_info *map_context);
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typedef void (*dm_flush_fn) (struct dm_target *ti);
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typedef void (*dm_presuspend_fn) (struct dm_target *ti);
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@ -75,6 +80,13 @@ typedef int (*dm_ioctl_fn) (struct dm_target *ti, unsigned int cmd,
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typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
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struct bio_vec *biovec, int max_size);
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/*
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* Returns:
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* 0: The target can handle the next I/O immediately.
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* 1: The target can't handle the next I/O immediately.
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*/
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typedef int (*dm_busy_fn) (struct dm_target *ti);
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void dm_error(const char *message);
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/*
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@ -107,7 +119,9 @@ struct target_type {
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dm_ctr_fn ctr;
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dm_dtr_fn dtr;
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dm_map_fn map;
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dm_map_request_fn map_rq;
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dm_endio_fn end_io;
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dm_request_endio_fn rq_end_io;
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dm_flush_fn flush;
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dm_presuspend_fn presuspend;
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dm_postsuspend_fn postsuspend;
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@ -117,6 +131,7 @@ struct target_type {
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dm_message_fn message;
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dm_ioctl_fn ioctl;
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dm_merge_fn merge;
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dm_busy_fn busy;
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};
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struct io_restrictions {
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