On 07.08.19 16:46, Kevin Wolf wrote: > This fixes devices like IDE that can still start new requests from I/O > handlers in the CPU thread while the block backend is drained. > > The basic assumption is that in a drain section, no new requests should > be allowed through a BlockBackend (blk_drained_begin/end don't exist, > we get drain sections only on the node level). However, there are two > special cases where requests should not be queued: > > 1. Block jobs: We already make sure that block jobs are paused in a > drain section, so they won't start new requests. However, if the > drain_begin is called on the job's BlockBackend first, it can happen > that we deadlock because the job stays busy until it reaches a pause > point - which it can't if its requests aren't processed any more. > > The proper solution here would be to make all requests through the > job's filter node instead of using a BlockBackend. For now, just > disabling request queuing on the job BlockBackend is simpler. > > 2. In test cases where making requests through bdrv_* would be > cumbersome because we'd need a BdrvChild. As we already got the > functionality to disable request queuing from 1., use it in tests, > too, for convenience. > > Signed-off-by: Kevin Wolf <kw...@redhat.com> > --- > include/sysemu/block-backend.h | 1 + > block/backup.c | 1 + > block/block-backend.c | 53 ++++++++++++++++++++++++++++++++-- > block/commit.c | 2 ++ > block/mirror.c | 1 + > blockjob.c | 3 ++ > tests/test-bdrv-drain.c | 1 + > 7 files changed, 59 insertions(+), 3 deletions(-)
Reviewed-by: Max Reitz <mre...@redhat.com>
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