Am 27.11.2020 um 15:45 hat Vladimir Sementsov-Ogievskiy geschrieben:
Split out no-perm part of bdrv_set_backing_hd() as a separate
transaction action. Note the in case of existing BdrvChild we reuse it,
not recreate, just to do less actions.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
block.c | 111 +++++++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 89 insertions(+), 22 deletions(-)
diff --git a/block.c b/block.c
index 54fb6d24bd..617cba9547 100644
--- a/block.c
+++ b/block.c
@@ -101,6 +101,7 @@ static int bdrv_attach_child_common(BlockDriverState
*child_bs,
uint64_t perm, uint64_t shared_perm,
void *opaque, BdrvChild **child,
GSList **tran, Error **errp);
+static void bdrv_remove_backing(BlockDriverState *bs, GSList **tran);
static int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue
*queue, Error **errp);
@@ -3194,45 +3195,111 @@ static BdrvChildRole
bdrv_backing_role(BlockDriverState *bs)
}
}
+typedef struct BdrvSetBackingNoPermState {
+ BlockDriverState *bs;
+ BlockDriverState *backing_bs;
+ BlockDriverState *old_inherits_from;
+ GSList *attach_tran;
+} BdrvSetBackingNoPermState;
Why do we need the nested attach_tran instead of just including these
actions in the outer transaction?
+static void bdrv_set_backing_noperm_abort(void *opaque)
+{
+ BdrvSetBackingNoPermState *s = opaque;
+
+ if (s->backing_bs) {
+ s->backing_bs->inherits_from = s->old_inherits_from;
+ }
+
+ tran_abort(s->attach_tran);
+
+ bdrv_refresh_limits(s->bs, NULL);
+ if (s->old_inherits_from) {
+ bdrv_refresh_limits(s->old_inherits_from, NULL);
+ }
How is bs->inherits_from related to limits? I don't see a
bdrv_refresh_limits() call in bdrv_set_backing_noperm() that this would
undo.
+}
+
+static void bdrv_set_backing_noperm_commit(void *opaque)
+{
+ BdrvSetBackingNoPermState *s = opaque;
+
+ tran_commit(s->attach_tran);
+}
+
+static TransactionActionDrv bdrv_set_backing_noperm_drv = {
+ .abort = bdrv_set_backing_noperm_abort,
+ .commit = bdrv_set_backing_noperm_commit,
+ .clean = g_free,
+};
+
/*
* Sets the bs->backing link of a BDS. A new reference is created; callers
* which don't need their own reference any more must call bdrv_unref().
*/
-void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
- Error **errp)
+static int bdrv_set_backing_noperm(BlockDriverState *bs,
+ BlockDriverState *backing_bs,
+ GSList **tran, Error **errp)
{
- bool update_inherits_from = bdrv_chain_contains(bs, backing_hd) &&
- bdrv_inherits_from_recursive(backing_hd, bs);
+ int ret = 0;
+ bool update_inherits_from = bdrv_chain_contains(bs, backing_bs) &&
+ bdrv_inherits_from_recursive(backing_bs, bs);
+ GSList *attach_tran = NULL;
+ BdrvSetBackingNoPermState *s;
if (bdrv_is_backing_chain_frozen(bs, child_bs(bs->backing), errp)) {
- return;
+ return -EPERM;
}
- if (backing_hd) {
- bdrv_ref(backing_hd);
+ if (bs->backing && backing_bs) {
+ bdrv_replace_child_safe(bs->backing, backing_bs, tran);
+ } else if (bs->backing && !backing_bs) {
+ bdrv_remove_backing(bs, tran);
+ } else if (backing_bs) {
+ assert(!bs->backing);
+ ret = bdrv_attach_child_noperm(bs, backing_bs, "backing",
+ &child_of_bds, bdrv_backing_role(bs),
+ &bs->backing, &attach_tran, errp);
+ if (ret < 0) {
+ tran_abort(attach_tran);
This looks wrong to me, we'll call tran_abort() a second time through
bdrv_set_backing_noperm_abort() when the outer transaction aborts.
I also notice that the other two if branches do just add things to the
outer 'tran', it's just this branch that gets a nested one.
+ return ret;
+ }
}
- if (bs->backing) {
- /* Cannot be frozen, we checked that above */
- bdrv_unref_child(bs, bs->backing);
- bs->backing = NULL;
- }
+ s = g_new(BdrvSetBackingNoPermState, 1);
+ *s = (BdrvSetBackingNoPermState) {
+ .bs = bs,
+ .backing_bs = backing_bs,
+ .old_inherits_from = backing_bs ? backing_bs->inherits_from : NULL,
+ };
+ tran_prepend(tran, &bdrv_set_backing_noperm_drv, s);
- if (!backing_hd) {
- goto out;
+ /*
+ * If backing_bs 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).
Setting it to NULL was previously done by bdrv_unref_child().
bdrv_replace_child_safe() and bdrv_remove_backing() don't seem to do
this any more.