@@ -620,8 +620,11 @@ void bdrv_parent_drained_begin_single(BdrvChild *c, bool poll);
* bdrv_parent_drained_end_single:
*
* End a quiesced section for the parent of @c.
+ *
+ * If @poll is true, poll until the parent is unquiesced. This may
+ * lead to changes in the block graph.
*/
-void bdrv_parent_drained_end_single(BdrvChild *c);
+void bdrv_parent_drained_end_single(BdrvChild *c, bool poll);
/**
* bdrv_parent_drained_end:
@@ -670,6 +670,20 @@ struct BdrvChildRole {
void (*drained_begin)(BdrvChild *child);
void (*drained_end)(BdrvChild *child);
+ /*
+ * Parents that require polling to actually become unquiesced
+ * should implement this function in addition to .drained_end().
+ * In it, the parent should end the drain and aio_poll() until it
+ * is no longer quiesced.
+ *
+ * Thus, in contrast to .drained_end(), this function is allowed
+ * to change the graph.
+ *
+ * (This pointer may be NULL, in which case .drained_end() is
+ * called instead.)
+ */
+ void (*drained_end_unquiesce)(BdrvChild *child);
+
/*
* Returns whether the parent has pending requests for the child. This
* callback is polled after .drained_begin() has been called until all
@@ -2252,7 +2252,7 @@ static void bdrv_replace_child_noperm(BdrvChild *child,
child->role->detach(child);
}
while (child->parent_quiesce_counter) {
- bdrv_parent_drained_end_single(child);
+ bdrv_parent_drained_end_single(child, true);
}
QLIST_REMOVE(child, next_parent);
} else {
@@ -55,12 +55,16 @@ void bdrv_parent_drained_begin(BlockDriverState *bs, BdrvChild *ignore,
}
}
-void bdrv_parent_drained_end_single(BdrvChild *c)
+void bdrv_parent_drained_end_single(BdrvChild *c, bool poll)
{
assert(c->parent_quiesce_counter > 0);
c->parent_quiesce_counter--;
if (c->role->drained_end) {
- c->role->drained_end(c);
+ if (poll && c->role->drained_end_unquiesce) {
+ c->role->drained_end_unquiesce(c);
+ } else {
+ c->role->drained_end(c);
+ }
}
}
@@ -73,7 +77,7 @@ void bdrv_parent_drained_end(BlockDriverState *bs, BdrvChild *ignore,
if (c == ignore || (ignore_bds_parents && c->role->parent_is_bds)) {
continue;
}
- bdrv_parent_drained_end_single(c);
+ bdrv_parent_drained_end_single(c, false);
}
}
This function has two callers; one wants it to poll, the other does not. To implement this parameter, we also need a new BdrvChildRole method, namely .drained_end_unquiesce(). This function differs from .drained_end() in that it should poll and is thus allowed to modify the block graph. Note that currently every BDS child's .drained_end() implementation is simply broken in exactly that regard; the current implementation is actually fit for .drained_end_unquiesce(). However, at this point we cannot implement .drained_end() correctly, so a later patch in this series will address that issue. Signed-off-by: Max Reitz <mreitz@redhat.com> --- include/block/block.h | 5 ++++- include/block/block_int.h | 14 ++++++++++++++ block.c | 2 +- block/io.c | 10 +++++++--- 4 files changed, 26 insertions(+), 5 deletions(-)