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author | Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> | 2020-05-28 12:43:59 +0300 |
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committer | Max Reitz <mreitz@redhat.com> | 2020-07-06 10:32:38 +0200 |
commit | 2c060c0f50220bebabacccb8e321df049cca602e (patch) | |
tree | 235970fa1d626a9374579a18c27a2798087872f9 /util/bitmap.c | |
parent | 2ea0332f427e3c6582a6c82130814c0d4c9ceb40 (diff) |
block/vpc: return ZERO block-status when appropriate
In case when get_image_offset() returns -1, we do zero out the
corresponding chunk of qiov. So, this should be reported as ZERO.
Note that this changes visible output of "qemu-img map --output=json"
and "qemu-io -c map" commands. For qemu-img map, the change is obvious:
we just mark as zero what is really zero. For qemu-io it's less
obvious: what was unallocated now is allocated.
There is an inconsistency in understanding of unallocated regions in
Qemu: backing-supporting format-drivers return 0 block-status to report
go-to-backing logic for this area. Some protocol-drivers (iscsi) return
0 to report fs-unallocated-non-zero status (i.e., don't occupy space on
disk, read result is undefined).
BDRV_BLOCK_ALLOCATED is defined as something more close to
go-to-backing logic. Still it is calculated as ZERO | DATA, so 0 from
iscsi is treated as unallocated. It doesn't influence backing-chain
behavior, as iscsi can't have backing file. But it does influence
"qemu-io -c map".
We should solve this inconsistency at some future point. Now, let's
just make backing-not-supporting format drivers (vdi in the previous
patch and vpc now) to behave more like backing-supporting drivers
and not report 0 block-status. More over, returning ZERO status is
absolutely valid thing, and again, corresponds to how the other
format-drivers (backing-supporting) work.
After block-status update, it never reports 0, so setting
unallocated_blocks_are_zero doesn't make sense (as the only user of it
is bdrv_co_block_status and it checks unallocated_blocks_are_zero only
for unallocated areas). Drop it.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200528094405.145708-5-vsementsov@virtuozzo.com>
[mreitz: qemu-io -c map as used by iotest 146 now reports everything as
allocated; in order to make the test do something useful, we
use qemu-img map --output=json now]
Signed-off-by: Max Reitz <mreitz@redhat.com>
Diffstat (limited to 'util/bitmap.c')
0 files changed, 0 insertions, 0 deletions