[PATCH 1/7] dm: don't change md if dm_table_set_restrictions() fails

Benjamin Marzinski
2025-03-09T22:29:10Z

__bind was changing the disk capacity, geometry and mempools of the
mapped device before calling dm_table_set_restrictions() which could
fail, forcing dm to drop the new table. Failing here would leave the
device using the old table but with the wrong capacity and mempools.

Move dm_table_set_restrictions() earlier in __bind(). Since it needs the
capacity to be set, save the old version and restore it on failure.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
---
drivers/md/dm.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 5ab7574c0c76..f5c5ccb6f8d2 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2421,21 +2421,29 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
struct queue_limits *limits)
{
struct dm_table *old_map;
- sector_t size;
+ sector_t size, old_size;
int ret;

lockdep_assert_held(&md->suspend_lock);

size = dm_table_get_size(t);

+ old_size = dm_get_size(md);
+ set_capacity(md->disk, size);
+
+ ret = dm_table_set_restrictions(t, md->queue, limits);
+ if (ret) {
+ set_capacity(md->disk, old_size);
+ old_map = ERR_PTR(ret);
+ goto out;
+ }
+
/*
* Wipe any geometry if the size of the table changed.
*/
- if (size != dm_get_size(md))
+ if (size != old_size)
memset(&md->geometry, 0, sizeof(md->geometry));

- set_capacity(md->disk, size);
-
dm_table_event_callback(t, event_callback, md);

if (dm_table_request_based(t)) {
@@ -2468,12 +2476,6 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
t->mempools = NULL;
}

- ret = dm_table_set_restrictions(t, md->queue, limits);
- if (ret) {
- old_map = ERR_PTR(ret);
- goto out;
- }
-
old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
rcu_assign_pointer(md->map, (void *)t);
md->immutable_target_type = dm_table_get_immutable_target_type(t);
--
2.48.1