qcow2: Add incompatibility note between backing files and raw external data files

Backing files and raw external data files are mutually exclusive.
The documentation of the raw external data bit (in autoclear_features)
already indicates that, but we should also mention it on the other
side.

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Alberto Garcia <berto@igalia.com>
Message-Id: <20200410121816.8334-1-berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Alberto Garcia 2020-04-10 14:18:15 +02:00 committed by Kevin Wolf
parent 16aaacb307
commit a50c1f57e4

View File

@ -25,6 +25,9 @@ The first cluster of a qcow2 image contains the file header:
is stored (NB: The string is not null terminated). 0 if the is stored (NB: The string is not null terminated). 0 if the
image doesn't have a backing file. image doesn't have a backing file.
Note: backing files are incompatible with raw external data
files (auto-clear feature bit 1).
16 - 19: backing_file_size 16 - 19: backing_file_size
Length of the backing file name in bytes. Must not be Length of the backing file name in bytes. Must not be
longer than 1023 bytes. Undefined if the image doesn't have longer than 1023 bytes. Undefined if the image doesn't have