Re: [Qemu-devel] [PATCH v4 00/14] qemu-img map: Allow driver to return file of the allocated block

[Max Reitz <mreitz@redhat.com>]

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On 24.12.2015 06:50, Fam Zheng wrote:
> v4: Rebase and resend, adding Eric's and Stefan's reviewed-by.
> 
>     Fix one typo in patch 13.
> 
>     Drop previous patch 14 for a later rework because it is not a hard
>     requirement, but it is pending on Eric's QAPI-to-JSON visitor series:
> 
>     https://lists.gnu.org/archive/html/qemu-devel/2015-12/msg03929.html
> 
> v3: Add Eric's rev-by in patches 6, 7, 13, 14.
>     12: New, split out from the previous 13.
>     12->13: Refactor "entry_mergable" from imp_map().
>         Don't mess the merge conditions. [Paolo]
>         Address Eric's comments:
>         - Check has_foo before using foo.
>         - Remove blank line between comments and definition in schema.
>         - Use PRId64 instead of %ld.
>         - Merge short lines.
> 
> v2: Add Eric's rev-by in patches 2, 4, 5.
>     01: Refering -> referring in commit message. [Eric]
>         Recurse to "file" for sensible "zero" flag. [Paolo]
>     12: New. Make MapEntry a QAPI struct. [Paolo, Markus]
> 
> Original cover letter
> ---------------------
> 
> I stumbled upon this when looking at external bitmap formats.
> 
> Current "qemu-img map" command only displays filename if the data is allocated
> in bs (bs->file) itself, or in the backing chain. Otherwise, it displays an
> unfriendly error message:
> 
>     $ qemu-img create -f vmdk -o subformat=monolithicFlat /tmp/test.vmdk 1G
> 
>     $ qemu-img map /tmp/test.vmdk
>     Offset          Length          Mapped to       File
>     qemu-img: File contains external, encrypted or compressed clusters.
> 
> This can be improved. This series extends the .bdrv_co_get_block_status
> callback, to let block driver return the BDS of file; then updates all driver
> to implement it; and lastly, it changes qemu-img to use this information in
> "map" command:
> 
> 
>     $ qemu-img map /tmp/test.vmdk
>     Offset          Length          Mapped to       File
>     0               0x40000000      0               /tmp/test-flat.vmdk
> 
>     $ qemu-img map --output json /tmp/test.vmdk
>     [{"length": 1073741824, "start": 0, "zero": false, "offset": 0, "depth": 0,
>       "file": "/tmp/test-flat.vmdk", "data": true}
>     ]
> 
> Fam Zheng (14):
>   block: Add "file" output parameter to block status query functions
>   qcow: Assign bs->file->bs to file in qcow_co_get_block_status
>   qcow2: Assign bs->file->bs to file in qcow2_co_get_block_status

Minor comment: I'd swap these two patches (2 and 3). Patch 1 breaks test
102, patch 3 fixes it again. It would be better to break it for as short
a time as possible.

Alternatively, in order not to break 102 at all, patch 1 would need to
leave the "if (bs->file &&" part of bdrv_co_get_block_status()
(@@ -1544,13 +1550,14 @@) as-is and change it only after the format
block drivers set *file.

Max

>   raw: Assign bs to file in raw_co_get_block_status
>   iscsi: Assign bs to file in iscsi_co_get_block_status
>   parallels: Assign bs->file->bs to file in
>     parallels_co_get_block_status
>   qed: Assign bs->file->bs to file in bdrv_qed_co_get_block_status
>   sheepdog: Assign bs to file in sd_co_get_block_status
>   vdi: Assign bs->file->bs to file in vdi_co_get_block_status
>   vpc: Assign bs->file->bs to file in vpc_co_get_block_status
>   vmdk: Return extent's file in bdrv_get_block_status
>   qemu-img: In "map", use the returned "file" from bdrv_get_block_status
>   qemu-img: Make MapEntry a QAPI struct
>   iotests: Add "qemu-img map" test for VMDK extents
> 
>  block/io.c                 | 42 ++++++++++++++++---------
>  block/iscsi.c              |  9 ++++--
>  block/mirror.c             |  3 +-
>  block/parallels.c          |  3 +-
>  block/qcow.c               |  3 +-
>  block/qcow2.c              |  3 +-
>  block/qed.c                |  6 +++-
>  block/raw-posix.c          |  4 ++-
>  block/raw_bsd.c            |  4 ++-
>  block/sheepdog.c           |  5 ++-
>  block/vdi.c                |  3 +-
>  block/vmdk.c               | 13 ++++----
>  block/vpc.c                |  4 ++-
>  block/vvfat.c              |  2 +-
>  include/block/block.h      |  6 ++--
>  include/block/block_int.h  |  3 +-
>  qapi/block-core.json       | 27 ++++++++++++++++
>  qemu-img.c                 | 78 ++++++++++++++++++++++++++++------------------
>  tests/qemu-iotests/059     | 10 ++++++
>  tests/qemu-iotests/059.out | 38 ++++++++++++++++++++++
>  20 files changed, 198 insertions(+), 68 deletions(-)
> 



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