dm cache policy mq: protect residency method with existing mutex
It is safe to use a mutex in mq_residency() at this point since it is
only called from ioctl context. But future-proof mq_residency() by
using might_sleep() to catch new contexts that cannot sleep.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c
index 4296155..db490f7 100644
--- a/drivers/md/dm-cache-policy-mq.c
+++ b/drivers/md/dm-cache-policy-mq.c
@@ -1001,10 +1001,14 @@
static dm_cblock_t mq_residency(struct dm_cache_policy *p)
{
+ dm_cblock_t r;
struct mq_policy *mq = to_mq_policy(p);
- /* FIXME: lock mutex, not sure we can block here */
- return to_cblock(mq->nr_cblocks_allocated);
+ mutex_lock(&mq->lock);
+ r = to_cblock(mq->nr_cblocks_allocated);
+ mutex_unlock(&mq->lock);
+
+ return r;
}
static void mq_tick(struct dm_cache_policy *p)