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dm: support barriers on simple devices

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Implement barrier support for single device DM devices

This patch implements barrier support in DM for the common case of dm linear
just remapping a single underlying device. In this case we can safely
pass the barrier through because there can be no reordering between
devices.

 NB. Any DM device might cease to support barriers if it gets
     reconfigured so code must continue to allow for a possible
     -EOPNOTSUPP on every barrier bio submitted.  - agk

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Andi Kleen
2009-01-06 03:05:09 +00:00
committed by Alasdair G Kergon
parent 7d76345da6
commit ab4c142488
5 changed files with 33 additions and 10 deletions
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7
include/linux/device-mapper.h
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@@ -112,7 +112,14 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d);
/*
* Information about a target type
*/
/*
* Target features
*/
#define DM_TARGET_SUPPORTS_BARRIERS 0x00000001
struct target_type {
uint64_t features;
const char *name;
struct module *module;
unsigned version[3];