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block: Make bdrv_root_attach_child() unref child_bs on failure

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A consequence of the previous patch is that bdrv_attach_child()
transfers the reference to child_bs from the caller to parent_bs,
which will drop it on bdrv_close() or when someone calls
bdrv_unref_child().

But this only happens when bdrv_attach_child() succeeds. If it fails
then the caller is responsible for dropping the reference to child_bs.

This patch makes bdrv_attach_child() take the reference also when
there is an error, freeing the caller for having to do it.

A similar situation happens with bdrv_root_attach_child(), so the
changes on this patch affect both functions.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Message-id: 20dfb3d9ccec559cdd1a9690146abad5d204a186.1557754872.git.berto@igalia.com
[mreitz: Removed now superfluous BdrvChild * variable in
         bdrv_open_child()]
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Alberto Garcia 2019-05-13 16:46:18 +03:00 • committed by Max Reitz
parent dd4118c792
commit b441dc71c0
4 changed files with 20 additions and 16 deletions
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30
block.c
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@ -2243,6 +2243,13 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs)
}
}
/*
* This function steals the reference to child_bs from the caller.
* That reference is later dropped by bdrv_root_unref_child().
*
* On failure NULL is returned, errp is set and the reference to
* child_bs is also dropped.
*/
BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
const char *child_name,
const BdrvChildRole *child_role,
@ -2255,6 +2262,7 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
ret = bdrv_check_update_perm(child_bs, NULL, perm, shared_perm, NULL, errp);
if (ret < 0) {
bdrv_abort_perm_update(child_bs);
bdrv_unref(child_bs);
return NULL;
}
@ -2274,6 +2282,14 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
return child;
}
/*
* This function transfers the reference to child_bs from the caller
* to parent_bs. That reference is later dropped by parent_bs on
* bdrv_close() or if someone calls bdrv_unref_child().
*
* On failure NULL is returned, errp is set and the reference to
* child_bs is also dropped.
*/
BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
BlockDriverState *child_bs,
const char *child_name,
@ -2401,12 +2417,9 @@ void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
/* If backing_hd was already part of bs's backing chain, and
* inherits_from pointed recursively to bs then let's update it to
* point directly to bs (else it will become NULL). */
if (update_inherits_from) {
if (bs->backing && update_inherits_from) {
backing_hd->inherits_from = bs;
}
if (!bs->backing) {
bdrv_unref(backing_hd);
}
out:
bdrv_refresh_limits(bs, NULL);
@ -2594,7 +2607,6 @@ BdrvChild *bdrv_open_child(const char *filename,
const BdrvChildRole *child_role,
bool allow_none, Error **errp)
{
BdrvChild *c;
BlockDriverState *bs;
bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_role,
@ -2603,13 +2615,7 @@ BdrvChild *bdrv_open_child(const char *filename,
return NULL;
}
c = bdrv_attach_child(parent, bs, bdref_key, child_role, errp);
if (!c) {
bdrv_unref(bs);
return NULL;
}
return c;
return bdrv_attach_child(parent, bs, bdref_key, child_role, errp);
}
/* TODO Future callers may need to specify parent/child_role in order for