From: Eric Dumazet <eduma...@google.com>
rcu_dereference() should be used in sections protected by rcu_read_lock.
For writers, holding some kind of mutex or lock,
rcu_dereference_protected() is the way to go, adding explicit lockdep
bits.
In __unbind(), we are the last user of this mapped device, so can use
the constant '1' instead of a lockdep_is_held(), not consistent with
other uses of rcu_dereference_protected() which use md->suspend_lock
mutex.
Reported-by: Kirill A. Shutemov <kir...@shutemov.name>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Fixes: 33423974bfc1 ("dm: Use rcu_dereference() for accessing rcu pointer")
Cc: Pranith Kumar <bobby.pr...@gmail.com>
Cc: Mike Snitzer <snit...@redhat.com>
---
v2: changed all buggy rcu_dereference()
BTW, having a mutex named suspend_lock is ugly, IMO.
drivers/md/dm.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index a0ece87ad426..5919d933bce9 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2335,7 +2335,8 @@ static struct dm_table *__bind(struct mapped_device *md,
struct dm_table *t,
merge_is_optional = dm_table_merge_is_optional(t);
- old_map = rcu_dereference(md->map);
+ old_map = rcu_dereference_protected(md->map,
+ lockdep_is_held(&md->suspend_lock));
rcu_assign_pointer(md->map, t);
md->immutable_target_type = dm_table_get_immutable_target_type(t);
@@ -2355,7 +2356,7 @@ static struct dm_table *__bind(struct mapped_device *md,
struct dm_table *t,
*/
static struct dm_table *__unbind(struct mapped_device *md)
{
- struct dm_table *map = rcu_dereference(md->map);
+ struct dm_table *map = rcu_dereference_protected(md->map, 1);
if (!map)
return NULL;
@@ -2850,7 +2851,8 @@ retry:
goto retry;
}
- map = rcu_dereference(md->map);
+ map = rcu_dereference_protected(md->map,
+ lockdep_is_held(&md->suspend_lock));
r = __dm_suspend(md, map, suspend_flags, TASK_INTERRUPTIBLE);
if (r)
@@ -2908,7 +2910,8 @@ retry:
goto retry;
}
- map = rcu_dereference(md->map);
+ map = rcu_dereference_protected(md->map,
+ lockdep_is_held(&md->suspend_lock));
if (!map || !dm_table_get_size(map))
goto out;
@@ -2943,7 +2946,8 @@ static void __dm_internal_suspend(struct mapped_device
*md, unsigned suspend_fla
return; /* nest suspend */
}
- map = rcu_dereference(md->map);
+ map = rcu_dereference_protected(md->map,
+ lockdep_is_held(&md->suspend_lock));
/*
* Using TASK_UNINTERRUPTIBLE because only NOFLUSH internal suspend is
--
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