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Re: [Qemu-block] [PATCH v5 30/42] qemu-img: Use child access functions
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] [PATCH v5 30/42] qemu-img: Use child access functions |
Date: |
Wed, 19 Jun 2019 17:49:40 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 |
On 19.06.19 11:18, Vladimir Sementsov-Ogievskiy wrote:
> 13.06.2019 1:09, Max Reitz wrote:
>> This changes iotest 204's output, because blkdebug on top of a COW node
>> used to make qemu-img map disregard the rest of the backing chain (the
>> backing chain was broken by the filter). With this patch, the
>> allocation in the base image is reported correctly.
>>
>> Signed-off-by: Max Reitz <address@hidden>
>> ---
>> qemu-img.c | 36 ++++++++++++++++++++----------------
>> tests/qemu-iotests/204.out | 1 +
>> 2 files changed, 21 insertions(+), 16 deletions(-)
>>
>> diff --git a/qemu-img.c b/qemu-img.c
>> index 07b6e2a808..7bfa6e5d40 100644
>> --- a/qemu-img.c
>> +++ b/qemu-img.c
>> @@ -992,7 +992,7 @@ static int img_commit(int argc, char **argv)
>> if (!blk) {
>> return 1;
>> }
>> - bs = blk_bs(blk);
>> + bs = bdrv_skip_implicit_filters(blk_bs(blk));
>
> if filename is json, describing explicit filter over normal node, bs will be
> explicit filter ...
>
>>
>> qemu_progress_init(progress, 1.f);
>> qemu_progress_print(0.f, 100);
>> @@ -1009,7 +1009,7 @@ static int img_commit(int argc, char **argv)
>> /* This is different from QMP, which by default uses the deepest
>> file in
>> * the backing chain (i.e., the very base); however, the
>> traditional
>> * behavior of qemu-img commit is using the immediate backing
>> file. */
>> - base_bs = backing_bs(bs);
>> + base_bs = bdrv_filtered_cow_bs(bs);
>> if (!base_bs) {
>
> and here we'll fail.
Right, will change to bdrv_backing_chain_next().
>> error_setg(&local_err, "Image does not have a backing file");
>> goto done;
>> @@ -1626,19 +1626,18 @@ static int convert_iteration_sectors(ImgConvertState
>> *s, int64_t sector_num)
>>
>> if (s->sector_next_status <= sector_num) {
>> int64_t count = n * BDRV_SECTOR_SIZE;
>> + BlockDriverState *src_bs = blk_bs(s->src[src_cur]);
>> + BlockDriverState *base;
>>
>> if (s->target_has_backing) {
>> -
>> - ret = bdrv_block_status(blk_bs(s->src[src_cur]),
>> - (sector_num - src_cur_offset) *
>> - BDRV_SECTOR_SIZE,
>> - count, &count, NULL, NULL);
>> + base = bdrv_backing_chain_next(src_bs);
>
> As you described in another patch, will not we here get allocated in base as
> allocated, because of
> counting filters above base?
Damn, yes. So
base = bdrv_filtered_cow_bs(bdrv_skip_rw_filters(src_bs));
I suppose.
> Hmm. I now think, why filters don't report everything as unallocated, would
> not it be more correct
> than fallthrough to child?
I don’t know, actually. Maybe, maybe not.
>> } else {
>> - ret = bdrv_block_status_above(blk_bs(s->src[src_cur]), NULL,
>> - (sector_num - src_cur_offset) *
>> - BDRV_SECTOR_SIZE,
>> - count, &count, NULL, NULL);
>> + base = NULL;
>> }
>> + ret = bdrv_block_status_above(src_bs, base,
>> + (sector_num - src_cur_offset) *
>> + BDRV_SECTOR_SIZE,
>> + count, &count, NULL, NULL);
>> if (ret < 0) {
>> error_report("error while reading block status of sector %"
>> PRId64
>> ": %s", sector_num, strerror(-ret));
[...]
>> @@ -2949,7 +2950,7 @@ static int img_map(int argc, char **argv)
>> if (!blk) {
>> return 1;
>> }
>> - bs = blk_bs(blk);
>> + bs = bdrv_skip_implicit_filters(blk_bs(blk));
>
> Hmm, another thought about implicit filters, how they could be here in
> qemu-img?
Hm, I don’t think they can.
> If implicit are only
> job filters. Do you prepared it for implicit COR? But we discussed with Kevin
> that we'd better deprecate
> copy-on-read option..
>
> So, if implicit filters are for compatibility, we'll have them only in
> block-jobs. So, seems no reason to support
> them in qemu-img.
Seems reasonable, yes.
> Also, in block-jobs, we can abandon creating implicit filters above any
> filter nodes, as well as abandon creating any
> filter nodes above implicit filters. This will still support old scenarios,
> but gives very simple and well defined scope
> of using implicit filters and how to work with them. What do you think?
Hm, in what way would that make things simpler?
Max
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[Qemu-block] [PATCH v5 35/42] block: Fix check_to_replace_node(), Max Reitz, 2019/06/12
[Qemu-block] [PATCH v5 34/42] block: Inline bdrv_co_block_status_from_*(), Max Reitz, 2019/06/12
[Qemu-block] [PATCH v5 36/42] iotests: Add tests for mirror @replaces loops, Max Reitz, 2019/06/12
[Qemu-block] [PATCH v5 38/42] iotests: Let complete_and_wait() work with commit, Max Reitz, 2019/06/12
[Qemu-block] [PATCH v5 39/42] iotests: Add filter commit test cases, Max Reitz, 2019/06/12