mbox series

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

Message ID 20220216105355.30729-1-hreitz@redhat.com (mailing list archive)
Headers show
Series block: Make bdrv_refresh_limits() non-recursive | expand

Message

Hanna Czenczek Feb. 16, 2022, 10:53 a.m. UTC 
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

Comments

Stefan Hajnoczi Feb. 28, 2022, 2:42 p.m. UTC | #1 
On Wed, Feb 16, 2022 at 11:53:52AM +0100, Hanna Reitz wrote:
> 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
> 

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Kevin Wolf March 4, 2022, 1:36 p.m. UTC | #2 
Am 16.02.2022 um 11:53 hat Hanna Reitz geschrieben:
> 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.

Thanks, applied to the block branch.

Kevin