[PATCH blktests 0/3] test and handle concurrent IO scheduler switching

Until the recent kernel commit 4ff58d6bc9dd ("block: serialize elevator
changes for the same queue using a writer lock") concurrent writes to
the sysfs file queue/scheduler caused KASAN failures [1]. The first
patch of this series adds the regression test case for the fix.

After the kernel commit, writes to the file queue/scheduler can return
-EBUSY. This is rare but can happen when udevd writes to the file at
exactly the same timing as blktests test cases, and it results in
unexpected test failures. The other two patches in this series handle
-EBUSY and avoid the failures.

[1] https://lore.kernel.org/linux-block/[email protected]/

Shin'ichiro Kawasaki (3):
  block: add test for concurrent IO scheduler switching
  check: introduce _write_queue_sched() to repeat queue/scheduler writes
  common, block/{015,020,021,027,040}, zbd/012: use _write_queue_sched()

 check                      | 24 ++++++++++++++++++-
 common/dm                  |  2 +-
 common/multipath-over-rdma |  2 +-
 common/rc                  |  5 +---
 tests/block/015            |  2 +-
 tests/block/020            |  2 +-
 tests/block/021            |  2 +-
 tests/block/027            |  2 +-
 tests/block/040            |  3 +--
 tests/block/045            | 49 ++++++++++++++++++++++++++++++++++++++
 tests/block/045.out        |  2 ++
 tests/zbd/012              |  2 +-
 12 files changed, 83 insertions(+), 14 deletions(-)
 create mode 100755 tests/block/045
 create mode 100644 tests/block/045.out

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2.54.0