[PATCH v2 0/3] block: Make bdrv_refresh_limits() non-recursive

[Hanna Reitz]

Hi,

v1 with detailed reasoning:
https://lists.nongnu.org/archive/html/qemu-block/2022-02/msg00508.html

This series makes bdrv_refresh_limits() non-recursive so that it is
sufficient for callers to ensure that the node on which they call it
will not receive concurrent I/O requests (instead of ensuring the same
for the whole subtree).

We need to ensure such I/O does not happen because bdrv_refresh_limits()
is not atomic and will produce intermediate invalid values, which will
break concurrent I/O requests that read these values.


v2:
- Use separate `try` block to clean up in patch 2 instead of putting the
  `os.remove()` in the existing one (which would cause the second
  `os.remove()` to be skipped if the first one failed)


git-backport-diff against v1:

Key:
[----] : patches are identical
[####] : number of functional differences between upstream/downstream patch
[down] : patch is downstream-only
The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively

001/3:[----] [--] 'block: Make bdrv_refresh_limits() non-recursive'
002/3:[0005] [FC] 'iotests: Allow using QMP with the QSD'
003/3:[----] [--] 'iotests/graph-changes-while-io: New test'


Hanna Reitz (3):
  block: Make bdrv_refresh_limits() non-recursive
  iotests: Allow using QMP with the QSD
  iotests/graph-changes-while-io: New test

 block/io.c                                    |  4 -
 tests/qemu-iotests/iotests.py                 | 32 ++++++-
 .../qemu-iotests/tests/graph-changes-while-io | 91 +++++++++++++++++++
 .../tests/graph-changes-while-io.out          |  5 +
 4 files changed, 127 insertions(+), 5 deletions(-)
 create mode 100755 tests/qemu-iotests/tests/graph-changes-while-io
 create mode 100644 tests/qemu-iotests/tests/graph-changes-while-io.out

-- 
2.34.1