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Re: [PATCH for-4.2? 0/6] block: Fix resize (extending) of short overlays
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [PATCH for-4.2? 0/6] block: Fix resize (extending) of short overlays |
Date: |
Wed, 20 Nov 2019 15:49:19 +0000 |
20.11.2019 17:03, Kevin Wolf wrote:
> Consider the following scenario where the overlay is shorter than its
> backing file:
>
> base.qcow2: AAAAAAAA
> overlay.qcow2: BBBB
>
> When resizing (extending) overlay.qcow2, the new blocks should not stay
> unallocated and make the additional As from base.qcow2 visible like
> before this series, but zeros should be read.
>
> A similar case happens with the various variants of a commit job when an
> intermediate file is short (- for unallocated):
>
> base.qcow2: A-A-AAAA
> mid.qcow2: BB-B
> top.qcow2: C--C--C-
>
> After commit top.qcow2 to mid.qcow2, the following happens:
>
> mid.qcow2: CB-C00C0 (correct result)
> mid.qcow2: CB-C--C- (before this fix)
>
> Without the fix, blocks that previously read as zeros on top.qcow2
> suddenly turn into A.
Note, that committing to base should still be broken after these series,
and is fixed in my "[PATCH 0/4] fix & merge block_status_above and
is_allocated_above".
I think, I'll post a 5/4 patch, to add this case to your new test.
>
> Kevin Wolf (6):
> block: bdrv_co_do_pwrite_zeroes: 64 bit 'bytes' parameter
> block: truncate: Don't make backing file data visible
> iotests: Add qemu_io_log()
> iotests: Fix timeout in run_job()
> iotests: Support job-complete in run_job()
> iotests: Test committing to short backing file
>
> block/io.c | 31 ++++++-
> tests/qemu-iotests/274 | 131 +++++++++++++++++++++++++++++
> tests/qemu-iotests/274.out | 150 ++++++++++++++++++++++++++++++++++
> tests/qemu-iotests/group | 1 +
> tests/qemu-iotests/iotests.py | 11 ++-
> 5 files changed, 319 insertions(+), 5 deletions(-)
> create mode 100755 tests/qemu-iotests/274
> create mode 100644 tests/qemu-iotests/274.out
>
--
Best regards,
Vladimir
- Re: [PATCH 5/6] iotests: Support job-complete in run_job(), (continued)
- Re: [PATCH for-4.2? 0/6] block: Fix resize (extending) of short overlays,
Vladimir Sementsov-Ogievskiy <=