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authorKevin Wolf <kwolf@redhat.com>2019-04-15 16:25:01 +0200
committerKevin Wolf <kwolf@redhat.com>2019-04-30 15:29:00 +0200
commitf29fbf7c6b1c9a84f6931c1c222716fbe073e6e4 (patch)
tree10fec182079ffb17a7acdcdaf91a9c5d2b8ba01f /python
parentde38b5005e946aa3714963ea4c501e279e7d3666 (diff)
downloadfocaccia-qemu-f29fbf7c6b1c9a84f6931c1c222716fbe073e6e4.tar.gz
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qcow2: Avoid COW during metadata preallocation
Limiting the allocation to INT_MAX bytes isn't particularly clever
because it means that the final cluster will be a partial cluster which
will be completed through a COW operation. This results in unnecessary
data read and write requests which lead to an unwanted non-sparse
filesystem block for metadata preallocation.

Align the maximum allocation size down to the cluster size to avoid this
situation.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Diffstat (limited to 'python')
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