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block: Add bdrv_make_empty()

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Right now, all users of bdrv_make_empty() call the BlockDriver method
directly.  That is not only bad style, it is also wrong, unless the
caller has a BdrvChild with a WRITE or WRITE_UNCHANGED permission.
(WRITE_UNCHANGED suffices, because callers generally use this function
to clear a node with a backing file after a commit operation.)

Introduce bdrv_make_empty() that verifies that it does.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200429141126.85159-2-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2020-04-29 16:11:23 +02:00 committed by Kevin Wolf
parent 19b7868eff
commit 6f7a3b535f
2 changed files with 24 additions and 0 deletions
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23
block.c
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@ -6764,3 +6764,26 @@ void bdrv_del_child(BlockDriverState *parent_bs, BdrvChild *child, Error **errp)
parent_bs->drv->bdrv_del_child(parent_bs, child, errp);
}
int bdrv_make_empty(BdrvChild *c, Error **errp)
{
BlockDriver *drv = c->bs->drv;
int ret;
assert(c->perm & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED));
if (!drv->bdrv_make_empty) {
error_setg(errp, "%s does not support emptying nodes",
drv->format_name);
return -ENOTSUP;
}
ret = drv->bdrv_make_empty(c->bs);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to empty %s",
c->bs->filename);
return ret;
}
return 0;
}

1
include/block/block.h
View File

@ -352,6 +352,7 @@ BlockMeasureInfo *bdrv_measure(BlockDriver *drv, QemuOpts *opts,
void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);
void bdrv_refresh_limits(BlockDriverState *bs, Error **errp);
int bdrv_commit(BlockDriverState *bs);
int bdrv_make_empty(BdrvChild *c, Error **errp);
int bdrv_change_backing_file(BlockDriverState *bs,
const char *backing_file, const char *backing_fmt);
void bdrv_register(BlockDriver *bdrv);