Before table_load() stages an inactive table check if its type
conflicts with a previously established device type (md->type).
Allowed md->type transitions:
DM_TYPE_NONE => DM_TYPE_BIO_BASED
DM_TYPE_NONE => DM_TYPE_REQUEST_BASED
Once a table load occurs the DM device's type is completely immutable.
This prevents a table reload from switching the inactive table directly
to a conflicting type (even if the table is explicitly cleared before
load).
Introduce 'type_lock' in mapped_device structure and use it to protect
md->type access. Use of mutex prepares for follow-on DM device queue
initialization changes that will allocate memory while md->type_lock
is held.
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Acked-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
---
v5: revised patch header, no code changes
drivers/md/dm-ioctl.c | 15 +++++++++++++++
drivers/md/dm.c | 37 ++++++++++++++++++++++++++++++-------
drivers/md/dm.h | 5 +++++
3 files changed, 50 insertions(+), 7 deletions(-)
Index: linux-2.6/drivers/md/dm-ioctl.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-ioctl.c
+++ linux-2.6/drivers/md/dm-ioctl.c
@@ -1176,6 +1176,21 @@ static int table_load(struct dm_ioctl *p
goto out;
}
+ /* Protect md->type against concurrent table loads. */
+ dm_lock_md_type(md);
+ if (dm_get_md_type(md) == DM_TYPE_NONE) {
+ /* initial table load, set md's type based on table's type */
+ dm_set_md_type(md, dm_table_get_type(t));
+ } else if (dm_get_md_type(md) != dm_table_get_type(t)) {
+ DMWARN("can't change device type after initial table load.");
+ dm_table_destroy(t);
+ dm_unlock_md_type(md);
+ r = -EINVAL;
+ goto out;
+ }
+ dm_unlock_md_type(md);
+
+ /* stage inactive table */
down_write(&_hash_lock);
hc = dm_get_mdptr(md);
if (!hc || hc->md != md) {
Index: linux-2.6/drivers/md/dm.c
===================================================================
--- linux-2.6.orig/drivers/md/dm.c
+++ linux-2.6/drivers/md/dm.c
@@ -123,6 +123,10 @@ struct mapped_device {
unsigned long flags;
struct request_queue *queue;
+ unsigned type;
+ /* Protect type against concurrent access. */
+ struct mutex type_lock;
+
struct gendisk *disk;
char name[16];
@@ -1874,8 +1878,10 @@ static struct mapped_device *alloc_dev(i
if (r < 0)
goto bad_minor;
+ md->type = DM_TYPE_NONE;
init_rwsem(&md->io_lock);
mutex_init(&md->suspend_lock);
+ mutex_init(&md->type_lock);
spin_lock_init(&md->deferred_lock);
spin_lock_init(&md->barrier_error_lock);
rwlock_init(&md->map_lock);
@@ -2128,6 +2134,30 @@ int dm_create(int minor, struct mapped_d
return 0;
}
+/*
+ * Functions to manage md->type.
+ * All are required to hold md->type_lock.
+ */
+void dm_lock_md_type(struct mapped_device *md)
+{
+ mutex_lock(&md->type_lock);
+}
+
+void dm_unlock_md_type(struct mapped_device *md)
+{
+ mutex_unlock(&md->type_lock);
+}
+
+void dm_set_md_type(struct mapped_device *md, unsigned type)
+{
+ md->type = type;
+}
+
+unsigned dm_get_md_type(struct mapped_device *md)
+{
+ return md->type;
+}
+
static struct mapped_device *dm_find_md(dev_t dev)
{
struct mapped_device *md;
@@ -2403,13 +2433,6 @@ struct dm_table *dm_swap_table(struct ma
goto out;
}
- /* cannot change the device type, once a table is bound */
- if (md->map &&
- (dm_table_get_type(md->map) != dm_table_get_type(table))) {
- DMWARN("can't change the device type after a table is bound");
- goto out;
- }
-
map = __bind(md, table, &limits);
out:
Index: linux-2.6/drivers/md/dm.h
===================================================================
--- linux-2.6.orig/drivers/md/dm.h
+++ linux-2.6/drivers/md/dm.h
@@ -66,6 +66,11 @@ int dm_table_alloc_md_mempools(struct dm
void dm_table_free_md_mempools(struct dm_table *t);
struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
+void dm_lock_md_type(struct mapped_device *md);
+void dm_unlock_md_type(struct mapped_device *md);
+void dm_set_md_type(struct mapped_device *md, unsigned type);
+unsigned dm_get_md_type(struct mapped_device *md);
+
/*
* To check the return value from dm_table_find_target().
*/
--
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