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block: pass bdrv_* methods to bs->file by default in block filters

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The following functions fail if bs->drv is a filter and does not
implement them:

bdrv_probe_blocksizes
bdrv_probe_geometry
bdrv_truncate
bdrv_has_zero_init
bdrv_get_info

Instead, the call should be passed to bs->file if it exists, to allow
filter drivers to support those methods without implementing them. This
commit makes `drv->is_filter = true` imply that these callbacks will be
forwarded to bs->file by default, so disabling support for these
functions must be done explicitly.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Manos Pitsidianakis 2017-07-13 18:30:25 +03:00 • committed by Kevin Wolf
parent 98bfaac788
commit 5a612c009e
2 changed files with 24 additions and 3 deletions
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6
include/block/block_int.h
View file

@ -87,7 +87,11 @@ struct BlockDriver {
const char *format_name;
int instance_size;
/* set to true if the BlockDriver is a block filter */
/* set to true if the BlockDriver is a block filter. Block filters pass
* certain callbacks that refer to data (see block.c) to their bs->file if
* the driver doesn't implement them. Drivers that do not wish to forward
* must implement them and return -ENOTSUP.
*/
bool is_filter;
/* for snapshots block filter like Quorum can implement the
* following recursive callback.