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dm: introduce num_flush_requests

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Introduce num_flush_requests for a target to set to say how many flush
instructions (empty barriers) it wants to receive.  These are sent by
__clone_and_map_empty_barrier with map_info->flush_request going from 0
to (num_flush_requests - 1).

Old targets without flush support won't receive any flush requests.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka
2009-06-22 10:12:20 +01:00
committed by Alasdair G Kergon
parent 27eaa14975
commit f9ab94cee3
2 changed files with 50 additions and 0 deletions
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11
include/linux/device-mapper.h
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@@ -21,6 +21,7 @@ typedef enum { STATUSTYPE_INFO, STATUSTYPE_TABLE } status_type_t;
union map_info {
void *ptr;
unsigned long long ll;
unsigned flush_request;
};
/*
@@ -167,6 +168,16 @@ struct dm_target {
/* Always a power of 2 */
sector_t split_io;
/*
* A number of zero-length barrier requests that will be submitted
* to the target for the purpose of flushing cache.
*
* The request number will be placed in union map_info->flush_request.
* It is a responsibility of the target driver to remap these requests
* to the real underlying devices.
*/
unsigned num_flush_requests;
/*
* These are automatically filled in by
* dm_table_get_device.