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

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
block.c
View File

@ -496,6 +496,8 @@ int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
if (drv && drv->bdrv_probe_blocksizes) {
return drv->bdrv_probe_blocksizes(bs, bsz);
} else if (drv && drv->is_filter && bs->file) {
return bdrv_probe_blocksizes(bs->file->bs, bsz);
}
return -ENOTSUP;
@ -513,6 +515,8 @@ int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo)
if (drv && drv->bdrv_probe_geometry) {
return drv->bdrv_probe_geometry(bs, geo);
} else if (drv && drv->is_filter && bs->file) {
return bdrv_probe_geometry(bs->file->bs, geo);
}
return -ENOTSUP;
@ -3426,11 +3430,15 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, PreallocMode prealloc,
assert(child->perm & BLK_PERM_RESIZE);
/* if bs->drv == NULL, bs is closed, so there's nothing to do here */
if (!drv) {
error_setg(errp, "No medium inserted");
return -ENOMEDIUM;
}
if (!drv->bdrv_truncate) {
if (bs->file && drv->is_filter) {
return bdrv_truncate(bs->file, offset, prealloc, errp);
}
error_setg(errp, "Image format driver does not support resize");
return -ENOTSUP;
}
@ -3767,6 +3775,9 @@ int bdrv_has_zero_init(BlockDriverState *bs)
if (bs->drv->bdrv_has_zero_init) {
return bs->drv->bdrv_has_zero_init(bs);
}
if (bs->file && bs->drv->is_filter) {
return bdrv_has_zero_init(bs->file->bs);
}
/* safe default */
return 0;
@ -3821,10 +3832,16 @@ void bdrv_get_backing_filename(BlockDriverState *bs,
int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
{
BlockDriver *drv = bs->drv;
if (!drv)
/* if bs->drv == NULL, bs is closed, so there's nothing to do here */
if (!drv) {
return -ENOMEDIUM;
if (!drv->bdrv_get_info)
}
if (!drv->bdrv_get_info) {
if (bs->file && drv->is_filter) {
return bdrv_get_info(bs->file->bs, bdi);
}
return -ENOTSUP;
}
memset(bdi, 0, sizeof(*bdi));
return drv->bdrv_get_info(bs, bdi);
}

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.