Re: [Qemu-devel] [PATCH 12/17] block: Convert bdrv_write() to BdrvChild

[Max Reitz]

On 27.06.2016 15:44, Max Reitz wrote:
> On 21.06.2016 11:21, Kevin Wolf wrote:
>> Signed-off-by: Kevin Wolf <address@hidden>
>> ---
>>  block/io.c             |  5 +++--
>>  block/qcow.c           | 10 +++++++++-
>>  block/qcow2-cluster.c  |  2 +-
>>  block/qcow2-refcount.c |  2 +-
>>  block/qcow2.c          | 10 +++++++++-
>>  block/vdi.c            |  4 ++--
>>  block/vvfat.c          |  5 ++---
>>  include/block/block.h  |  2 +-
>>  8 files changed, 28 insertions(+), 12 deletions(-)
> 
> Because I think this is better than saying "I won't give an R-b because
> of (1), (2)..." at the bottom:
> 
> Review key:
> [o] -- completely optional suggestion
> [r] -- request, optional, but I'll wait with an R-b until I get feedback
> [x] -- requires a fix
> 
> [...]
> 
>> diff --git a/block/qcow.c b/block/qcow.c
>> index e09827b..c80df78 100644
>> --- a/block/qcow.c
>> +++ b/block/qcow.c
>> @@ -969,7 +969,15 @@ static int qcow_write_compressed(BlockDriverState *bs, 
>> int64_t sector_num,
>>  
>>      if (ret != Z_STREAM_END || out_len >= s->cluster_size) {
>>          /* could not compress: write normal cluster */
>> -        ret = bdrv_write(bs, sector_num, buf, s->cluster_sectors);
>> +        QEMUIOVector qiov;
>> +        struct iovec iov = {
>> +            .iov_base   = (uint8_t*) buf,
> 
> [o] ERROR: "(foo*)" should be "(foo *)"
> 
> !!11!1elf
> 
>> +            .iov_len    = nb_sectors * BDRV_SECTOR_SIZE,
>> +        };
>> +        qemu_iovec_init_external(&qiov, &iov, 1);
>> +
>> +        ret = bs->drv->bdrv_co_writev(bs, sector_num, s->cluster_sectors,
>> +                                      &qiov);
> 
> [r] I'd use nb_sectors instead of s->cluster_sectors (or use
> s->cluster_sectors above), I think it should be the same variable in
> both places.
> 
> [o] Also, but this is a much weaker proposal, I'd have preferred a
> direct call to qcow_co_writev(). But maybe that's just me.

[x] qcow_write_compressed() is not a coroutine_fn, resulting in:

qemu-img: ./util/qemu-coroutine-lock.c:143: qemu_co_mutex_unlock:
Assertion `qemu_in_coroutine()' failed.

>>          if (ret < 0) {
>>              goto fail;
>>          }
> 
> [...]
> 
>> diff --git a/block/qcow2.c b/block/qcow2.c
>> index 4718f82..bc78af3 100644
>> --- a/block/qcow2.c
>> +++ b/block/qcow2.c
>> @@ -2597,7 +2597,15 @@ static int qcow2_write_compressed(BlockDriverState 
>> *bs, int64_t sector_num,
>>  
>>      if (ret != Z_STREAM_END || out_len >= s->cluster_size) {
>>          /* could not compress: write normal cluster */
>> -        ret = bdrv_write(bs, sector_num, buf, s->cluster_sectors);
>> +        QEMUIOVector qiov;
>> +        struct iovec iov = {
>> +            .iov_base   = (uint8_t*) buf,
> 
> [o] ERROR: "(foo*)" should be "(foo *)"
> 
>> +            .iov_len    = nb_sectors * BDRV_SECTOR_SIZE,
>> +        };
>> +        qemu_iovec_init_external(&qiov, &iov, 1);
>> +
>> +        ret = bs->drv->bdrv_co_writev(bs, sector_num, s->cluster_sectors,
>> +                                      &qiov);
> 
> [x] I don't think qcow2 has a bdrv_co_writev().
> 
> ($ dd if=/dev/urandom of=foo.raw bs=64k count=1
>  $ ./qemu-img convert -c -O qcow2 foo.raw foo.qcow2
> [1]    11808 segmentation fault (core dumped))
> 
> [r] Same as in qcow.c, I'd rather use nb_sectors instead of
> s->cluster_sectors.
> 
> [o] Same as in qcow.c, I'd call qcow2_co_pwritev() directly. Doing so
> would have prevented [x].

[x] Same as in qcow.c, qcow2_write_compressed() is not a coroutine_fn
either.

> Max
> 
>>          if (ret < 0) {
>>              goto fail;
>>          }
>

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