From: Max Reitz <mreitz@redhat.com>
To: qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Alberto Garcia <berto@igalia.com>,
qemu-devel@nongnu.org
Subject: Re: [PATCH for-4.2 0/2] qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK
Date: Wed, 6 Nov 2019 12:19:17 +0100 [thread overview]
Message-ID: <dc66ebe6-8e33-ce74-c408-7a57ee4f8331@redhat.com> (raw)
In-Reply-To: <20191028161841.1198-1-mreitz@redhat.com>
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On 28.10.19 17:18, Max Reitz wrote:
> This fixes a bug reported on
> https://bugs.launchpad.net/qemu/+bug/1850000. The problem is that
> QCOW2_COMPRESSED_SECTOR_MASK is a 32-bit mask when it really needs to be
> a 64-bit mask.
>
> The launchpad report mentions only problems with qemu-img check on large
> compressed images, but I think it might extend further than that:
> - I suppose qcow2_free_any_clusters() would free every compressed offset
> modulo 4G, which isn’t good
> - qcow2_update_snapshot_refcount() will probably update compressed
> cluster’s refcounts (in snapshots) modulo 4G, which also isn’t good
> - And then we have check_refcount_l2() which updates the wrong clusters
> for qemu-img check (as demonstrated in the bug report)
>
> - (qcow2_co_preadv_compressed() is safe because it uses the inverted
> mask, which of course is again just 32 bit)
>
>
> But I haven’t tested those other cases.
>
>
> Max Reitz (2):
> qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK
> iotests: Add test for 4G+ compressed qcow2 write
>
> block/qcow2.h | 2 +-
> tests/qemu-iotests/272 | 79 ++++++++++++++++++++++++++++++++++++++
> tests/qemu-iotests/272.out | 10 +++++
> tests/qemu-iotests/group | 1 +
> 4 files changed, 91 insertions(+), 1 deletion(-)
> create mode 100755 tests/qemu-iotests/272
> create mode 100644 tests/qemu-iotests/272.out
Thanks for the review, applied to my block branch:
https://git.xanclic.moe/XanClic/qemu/commits/branch/block
Max
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prev parent reply other threads:[~2019-11-06 11:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-28 16:18 [PATCH for-4.2 0/2] qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK Max Reitz
2019-10-28 16:18 ` [PATCH for-4.2 1/2] " Max Reitz
2019-10-28 16:18 ` [PATCH for-4.2 2/2] iotests: Add test for 4G+ compressed qcow2 write Max Reitz
2019-10-28 22:36 ` [PATCH for-4.2 0/2] qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK Alberto Garcia
2019-11-06 11:19 ` Max Reitz [this message]
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