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dm table: add always writeable feature

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Add a target feature flag DM_TARGET_ALWAYS_WRITEABLE to indicate that a target
does not support read-only mode.

The initial implementation of the thin provisioning target uses this.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Alasdair G Kergon 2011-10-31 20:19:02 +00:00
parent 3791e2fc0e
commit cc6cbe141a
2 changed files with 13 additions and 0 deletions
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6
drivers/md/dm-table.c
View File

@ -774,6 +774,12 @@ int dm_table_add_target(struct dm_table *t, const char *type,
t->singleton = 1;
}
if (dm_target_always_writeable(tgt->type) && !(t->mode & FMODE_WRITE)) {
DMERR("%s: target type %s may not be included in read-only tables",
dm_device_name(t->md), type);
return -EINVAL;
}
tgt->table = t;
tgt->begin = start;
tgt->len = len;

7
include/linux/device-mapper.h
View File

@ -166,6 +166,13 @@ struct target_type {
#define DM_TARGET_SINGLETON 0x00000001
#define dm_target_needs_singleton(type) ((type)->features & DM_TARGET_SINGLETON)
/*
* Indicates that a target does not support read-only devices.
*/
#define DM_TARGET_ALWAYS_WRITEABLE 0x00000002
#define dm_target_always_writeable(type) \
((type)->features & DM_TARGET_ALWAYS_WRITEABLE)
struct dm_target {
struct dm_table *table;
struct target_type *type;