On 15.10.2020 20:16, Andrey Shinkevich wrote:
On 14.10.2020 19:24, Max Reitz wrote:
On 12.10.20 19:43, Andrey Shinkevich wrote:
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--- block/stream.c | 93 +++++++++++++++++++++++++++++----------------- tests/qemu-iotests/030 | 51 +++---------------------- tests/qemu-iotests/030.out | 4 +- tests/qemu-iotests/141.out | 2 +- tests/qemu-iotests/245 | 19 +++++++--- 5 files changed, 81 insertions(+), 88 deletions(-)
Looks like stream_run() could be a bit streamlined now (the allocation checking should be unnecessary, unconditionally calling stream_populate() should be sufficient), but not necessary now.
That is what I had kept in my mind when I tackled this patch. But there is an underwater reef to streamline. Namely, how the block-stream job gets known about a long unallocated tail to exit the loop earlier in the stream_run(). Shall we return the '-EOF' or another error code from the cor_co_preadv_part() to be handled by the stream_run()? Any other suggestions, if any, will be appreciated.
diff --git a/block/stream.c b/block/stream.c index d3e1812..93564db 100644 --- a/block/stream.c +++ b/block/stream.c
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+ + cor_filter_bs = bdrv_cor_filter_append(bs, opts, BDRV_O_RDWR, errp); + if (cor_filter_bs == NULL) { + goto fail; + } + + if (bdrv_freeze_backing_chain(cor_filter_bs, bs, errp) < 0) {
Is there a reason why we can’t combine this with the bdrv_free_backing_chain() from bs down to above_base? I mean, the effect should be the same, just asking.
The bdrv_freeze_backing_chain(bs, above_base, errp) is called before the bdrv_reopen_set_read_only() to keep the backing chain safe during the context switch. Then we will want to freeze the 'COR -> TOP BS' link as well. Freezing/unfreezing parts is simlier to manage than doing that with the whole chain. If we decide to invoke the bdrv_reopen_set_read_only() after freezing the backing chain together with the COR-filter, we will not be able to get the 'write' permission on the read-only node.
+ bdrv_cor_filter_drop(cor_filter_bs); + cor_filter_bs = NULL; + goto fail; + } + + s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs, + BLK_PERM_CONSISTENT_READ, + basic_flags | BLK_PERM_WRITE | BLK_PERM_GRAPH_MOD,
Not that I’m an expert on the GRAPH_MOD permission, but why is this shared here but not below? Shouldn’t it be the same in both cases? (Same for taking it as a permission.)
When we invoke the block_job_add_bdrv(&s->common, "active node", bs,..) below (particularly, we need it to block the operations on the top node, bdrv_op_block_all()), we ask for the GRAPH_MOD permission for the top node. To allow that, the parent filter node should share that permission for the underlying node. Otherwise, we get assertion failed in the bdrv_check_update_perm() called from bdrv_replace_node() when we remove the filter.
I will add my comments above to the code. Andrey [...]