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blockjob: Make block_job_pause_all() keep a reference to the jobs
Starting from commit40840e419b
we are pausing all block jobs during bdrv_reopen_multiple() to prevent any of them from finishing and removing nodes from the graph while they are being reopened. It turns out that pausing a block job doesn't necessarily prevent it from finishing: a paused block job can still run its exit function from the main loop and call block_job_completed(). The mirror block job in particular always goes to the main loop while it is paused (by virtue of the bdrv_drained_begin() call in mirror_run()). Destroying a paused block job during bdrv_reopen_multiple() has two consequences: 1) The references to the nodes involved in the job are released, possibly destroying some of them. If those nodes were in the reopen queue this would trigger the problem originally described in commit40840e419b
, crashing QEMU. 2) At the end of bdrv_reopen_multiple(), bdrv_drain_all_end() would not be doing all necessary bdrv_parent_drained_end() calls. I can reproduce problem 1) easily with iotest 030 by increasing STREAM_BUFFER_SIZE from 512KB to 8MB in block/stream.c, or by tweaking the iotest like in this example: https://lists.gnu.org/archive/html/qemu-block/2017-11/msg00934.html This patch keeps an additional reference to all block jobs between block_job_pause_all() and block_job_resume_all(), guaranteeing that they are kept alive. Signed-off-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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parent
495566ec38
commit
3d5d319e12
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@ -730,6 +730,7 @@ void block_job_pause_all(void)
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AioContext *aio_context = blk_get_aio_context(job->blk);
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aio_context_acquire(aio_context);
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block_job_ref(job);
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block_job_pause(job);
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aio_context_release(aio_context);
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}
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@ -808,12 +809,14 @@ void coroutine_fn block_job_pause_point(BlockJob *job)
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void block_job_resume_all(void)
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{
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BlockJob *job = NULL;
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while ((job = block_job_next(job))) {
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BlockJob *job, *next;
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QLIST_FOREACH_SAFE(job, &block_jobs, job_list, next) {
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AioContext *aio_context = blk_get_aio_context(job->blk);
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aio_context_acquire(aio_context);
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block_job_resume(job);
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block_job_unref(job);
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aio_context_release(aio_context);
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}
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}
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