Re: [Qemu-devel] [PATCH v2 00/14] block: Remove "growable", add blk_new_open()

[Max Reitz <mreitz@redhat.com>]

On 2015-01-26 at 07:18, Stefano Stabellini wrote:
> On Thu, 22 Jan 2015, Max Reitz wrote:
>> This series removes the "growable" field from the BlockDriverState
>> object. Its use was to clamp guest requests against the limits of the
>> BDS; however, this can now be done more easily by moving those checks
>> into the BlockBackend functions.
>>
>> In a future series, "growable" may be reintroduced (maybe with a
>> different name); it will then signify whether a BDS is able to grow (in
>> contrast to the current "growable", which signifies whether it is
>> allowed to). Maybe I will add it to the BlockDriver instead of the BDS,
>> though.
>>
>> To be able to remove that field, qemu-io needs to be converted to
>> BlockBackend, which is done by this series as well. While working on
>> that I decided to convert blk_new_with_bs()+bdrv_open() to
>> blk_new_open(). I was skeptical about that decision at first, but it
>> seems good now that I was able to replace nearly every blk_new_with_bs()
>> call by blk_new_open(). In a future series I may try to convert some
>> remaining bdrv_open() calls to blk_new_open() as well. (And, in fact, in
>> a future series I *will* replace the last remaining blk_new_with_bs()
>> outside of blk_new_open() by blk_new_open().)
>>
>> Finally, the question needs to be asked: If, after this series, every
>> BDS is allowed to grow, are there any users which do not use BB, but
>> should still be disallowed from reading/writing beyond a BDS's limits?
>> The only users I could see were the block jobs. Some of them should
>> indeed be converted to BB; but none of them takes a user-supplied offset
>> or size, all work on the full BDS (or only on parts which have been
>> modified, etc.). Therefore, it is by design impossible for them to
>> exceed the BDS's limits, which makes making all BDS's growable safe.
> Hello Max,
> I applied the first four patches in this series, and this is what I get:
>
> hw/block/xen_disk.c: In function ‘blk_connect’:
> hw/block/xen_disk.c:907:27: error: implicit declaration of function ‘qstring_from_str’ [-Werror=implicit-function-declaration]
> hw/block/xen_disk.c:907:27: error: nested extern declaration of ‘qstring_from_str’ [-Werror=nested-externs]
> hw/block/xen_disk.c:907:27: error: invalid type argument of ‘->’ (have ‘int’)
> hw/block/xen_disk.c:901:22: error: unused variable ‘drv’ [-Werror=unused-variable]
> hw/block/xen_disk.c:900:23: error: unused variable ‘blk’ [-Werror=unused-variable]
>
> it would be great if you could build test it.

Sorry, of course I build test my patches, but I just don't have some 
subsystems enabled (there was no real reason not to have the Xen 
backends enabled, but that's just how it was; another example are 
Windows-specific areas), so I have to work blind on them. In this case I 
forgot to include the QMP type headers and to remove the now unused 
variables.

Thank you for looking at my patches and finding this issue! I'll send a 
fixed v3.

Max

>> v2:
>> - Rebased [Kevin]
>> - Patch 2: Added a TODO comment about removing @filename and @flags from
>>    blk_new_open() when possible [Kevin]
>>
>>
>> git-backport-diff against v1:
>>
>> Key:
>> [----] : patches are identical
>> [####] : number of functional differences between upstream/downstream patch
>> [down] : patch is downstream-only
>> The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively
>>
>> 001/14:[----] [--] 'block: Lift some BDS functions to the BlockBackend'
>> 002/14:[0006] [FC] 'block: Add blk_new_open()'
>> 003/14:[----] [-C] 'blockdev: Use blk_new_open() in blockdev_init()'
>> 004/14:[----] [--] 'block/xen: Use blk_new_open() in blk_connect()'
>> 005/14:[----] [--] 'qemu-img: Use blk_new_open() in img_open()'
>> 006/14:[----] [--] 'qemu-img: Use blk_new_open() in img_rebase()'
>> 007/14:[----] [--] 'qemu-img: Use BlockBackend as far as possible'
>> 008/14:[----] [--] 'qemu-nbd: Use blk_new_open() in main()'
>> 009/14:[----] [--] 'qemu-io: Use blk_new_open() in openfile()'
>> 010/14:[0002] [FC] 'qemu-io: Remove "growable" option'
>> 011/14:[----] [--] 'qemu-io: Use BlockBackend'
>> 012/14:[----] [--] 'block: Clamp BlockBackend requests'
>> 013/14:[----] [--] 'block: Remove "growable" from BDS'
>> 014/14:[----] [--] 'block: Keep bdrv_check*_request()'s return value'
>>
>>
>> Max Reitz (14):
>>    block: Lift some BDS functions to the BlockBackend
>>    block: Add blk_new_open()
>>    blockdev: Use blk_new_open() in blockdev_init()
>>    block/xen: Use blk_new_open() in blk_connect()
>>    qemu-img: Use blk_new_open() in img_open()
>>    qemu-img: Use blk_new_open() in img_rebase()
>>    qemu-img: Use BlockBackend as far as possible
>>    qemu-nbd: Use blk_new_open() in main()
>>    qemu-io: Use blk_new_open() in openfile()
>>    qemu-io: Remove "growable" option
>>    qemu-io: Use BlockBackend
>>    block: Clamp BlockBackend requests
>>    block: Remove "growable" from BDS
>>    block: Keep bdrv_check*_request()'s return value
>>
>>   block.c                        |  59 +++++-----
>>   block/block-backend.c          | 219 +++++++++++++++++++++++++++++++++++++
>>   block/qcow2.c                  |   6 --
>>   block/raw-posix.c              |   2 +-
>>   block/raw-win32.c              |   2 +-
>>   block/sheepdog.c               |   2 +-
>>   blockdev.c                     |  92 ++++++++--------
>>   hmp.c                          |   9 +-
>>   hw/block/xen_disk.c            |  24 ++---
>>   include/block/block_int.h      |   3 -
>>   include/qemu-io.h              |   4 +-
>>   include/sysemu/block-backend.h |  12 +++
>>   qemu-img.c                     | 171 ++++++++++++++---------------
>>   qemu-io-cmds.c                 | 238 ++++++++++++++++++++++-------------------
>>   qemu-io.c                      |  58 ++++------
>>   qemu-nbd.c                     |  25 ++---
>>   tests/qemu-iotests/016         |  73 -------------
>>   tests/qemu-iotests/016.out     |  23 ----
>>   tests/qemu-iotests/051.out     |  60 +++++------
>>   tests/qemu-iotests/087.out     |   8 +-
>>   tests/qemu-iotests/group       |   1 -
>>   21 files changed, 590 insertions(+), 501 deletions(-)
>>   delete mode 100755 tests/qemu-iotests/016
>>   delete mode 100644 tests/qemu-iotests/016.out
>>
>> -- 
>> 2.1.0
>>