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docs/qcow2: Limit refcount_order to [0, 6]

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Specify the upper limit of refcount_order to be 6 (that is,
refcount_bits = 64). Any larger value does not make much sense when all
offsets, sizes, cluster counts etc. "only" have a width of 64 bit as
well, and very large values would be very difficult to support.
Therefore, just cap it at the largest reasonable value.

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2014-09-03 00:25:09 +02:00 committed by Kevin Wolf
parent 4b318d6ca6
commit 7f75a07d50
1 changed files with 1 additions and 0 deletions
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docs/specs/qcow2.txt
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@ -110,6 +110,7 @@ in the description of a field.
in bits: refcount_bits = 1 << refcount_order). For version 2 in bits: refcount_bits = 1 << refcount_order). For version 2
images, the order is always assumed to be 4 images, the order is always assumed to be 4
(i.e. refcount_bits = 16). (i.e. refcount_bits = 16).
This value may not exceed 6 (i.e. refcount_bits = 64).
100 - 103: header_length 100 - 103: header_length
Length of the header structure in bytes. For version 2 Length of the header structure in bytes. For version 2