Hi,
This patchset contains two patches.
The first patch fixes a missed release of q->elevator_lock which was
mistakenly omitted in one of the return code path of ioc_qos_write.
The second patch fixes the locdep splat reported due to the incorrect
locking order between q->elevator_lock and q->rq_qos_mutex. The commit
245618f8e45f ("block: protect wbt_lat_usec using q->elevator_lock")
introduced q->elevator_lock to protect updates to blk-wbt parameters
when writing to the sysfs attribute wbt_lat_usec and the cgroup attribute
io.cost.qos. However, writes to these attributes also acquire q->rq_qos_
mutex, creating a potential circular dependency if the locking order is
not correctly followed. This patch ensures the correct locking sequence
to prevent such issues. Unfortunately, blktests currently lacks a test
case for writes to these attributes, which might have caught this issue
earlier. I plan to submit a blktest to cover these cases.
Nilay Shroff (2):
block: release q->elevator_lock in ioc_qos_write
block: correct locking order for protecting blk-wbt parameters
block/blk-cgroup.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++
block/blk-cgroup.h | 2 ++
block/blk-iocost.c | 17 +++++-----------
3 files changed, 58 insertions(+), 12 deletions(-)
--
2.47.1
