aboutsummaryrefslogtreecommitdiff
path: root/block.c
diff options
context:
space:
mode:
authorKevin Wolf <kwolf@redhat.com>2019-05-06 19:17:56 +0200
committerKevin Wolf <kwolf@redhat.com>2019-05-20 17:08:56 +0200
commit5d2318499fe980542fbc21d9ccbc127a6106017b (patch)
treeb69b4502f4d658bee21e7642c451eda22e15297a /block.c
parent25349e8250e67e7d126fbf0ad213811b62e7e529 (diff)
downloadqemu-5d2318499fe980542fbc21d9ccbc127a6106017b.zip
qemu-5d2318499fe980542fbc21d9ccbc127a6106017b.tar.gz
qemu-5d2318499fe980542fbc21d9ccbc127a6106017b.tar.bz2
block: Add bdrv_try_set_aio_context()
Eventually, we want to make sure that all parents and all children of a node are in the same AioContext as the node itself. This means that changing the AioContext may fail because one of the other involved parties (e.g. a guest device that was configured with an iothread) cannot allow switching to a different AioContext. Introduce a set of functions that allow to first check whether all involved nodes can switch to a new context and only then do the actual switch. The check recursively covers children and parents. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c92
1 files changed, 92 insertions, 0 deletions
diff --git a/block.c b/block.c
index 6999aad..8ff6ab1 100644
--- a/block.c
+++ b/block.c
@@ -936,6 +936,13 @@ static int bdrv_child_cb_inactivate(BdrvChild *child)
return 0;
}
+static bool bdrv_child_cb_can_set_aio_ctx(BdrvChild *child, AioContext *ctx,
+ GSList **ignore, Error **errp)
+{
+ BlockDriverState *bs = child->opaque;
+ return bdrv_can_set_aio_context(bs, ctx, ignore, errp);
+}
+
/*
* Returns the options and flags that a temporary snapshot should get, based on
* the originally requested flags (the originally requested image will have
@@ -1003,6 +1010,7 @@ const BdrvChildRole child_file = {
.attach = bdrv_child_cb_attach,
.detach = bdrv_child_cb_detach,
.inactivate = bdrv_child_cb_inactivate,
+ .can_set_aio_ctx = bdrv_child_cb_can_set_aio_ctx,
};
/*
@@ -1029,6 +1037,7 @@ const BdrvChildRole child_format = {
.attach = bdrv_child_cb_attach,
.detach = bdrv_child_cb_detach,
.inactivate = bdrv_child_cb_inactivate,
+ .can_set_aio_ctx = bdrv_child_cb_can_set_aio_ctx,
};
static void bdrv_backing_attach(BdrvChild *c)
@@ -1152,6 +1161,7 @@ const BdrvChildRole child_backing = {
.drained_end = bdrv_child_cb_drained_end,
.inactivate = bdrv_child_cb_inactivate,
.update_filename = bdrv_backing_update_filename,
+ .can_set_aio_ctx = bdrv_child_cb_can_set_aio_ctx,
};
static int bdrv_open_flags(BlockDriverState *bs, int flags)
@@ -5750,6 +5760,88 @@ void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context)
aio_context_release(new_context);
}
+static bool bdrv_parent_can_set_aio_context(BdrvChild *c, AioContext *ctx,
+ GSList **ignore, Error **errp)
+{
+ if (g_slist_find(*ignore, c)) {
+ return true;
+ }
+ *ignore = g_slist_prepend(*ignore, c);
+
+ /* A BdrvChildRole that doesn't handle AioContext changes cannot
+ * tolerate any AioContext changes */
+ if (!c->role->can_set_aio_ctx) {
+ char *user = bdrv_child_user_desc(c);
+ error_setg(errp, "Changing iothreads is not supported by %s", user);
+ g_free(user);
+ return false;
+ }
+ if (!c->role->can_set_aio_ctx(c, ctx, ignore, errp)) {
+ assert(!errp || *errp);
+ return false;
+ }
+ return true;
+}
+
+bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx,
+ GSList **ignore, Error **errp)
+{
+ if (g_slist_find(*ignore, c)) {
+ return true;
+ }
+ *ignore = g_slist_prepend(*ignore, c);
+ return bdrv_can_set_aio_context(c->bs, ctx, ignore, errp);
+}
+
+/* @ignore will accumulate all visited BdrvChild object. The caller is
+ * responsible for freeing the list afterwards. */
+bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx,
+ GSList **ignore, Error **errp)
+{
+ BdrvChild *c;
+
+ if (bdrv_get_aio_context(bs) == ctx) {
+ return true;
+ }
+
+ QLIST_FOREACH(c, &bs->parents, next_parent) {
+ if (!bdrv_parent_can_set_aio_context(c, ctx, ignore, errp)) {
+ return false;
+ }
+ }
+ QLIST_FOREACH(c, &bs->children, next) {
+ if (!bdrv_child_can_set_aio_context(c, ctx, ignore, errp)) {
+ return false;
+ }
+ }
+
+ return true;
+}
+
+int bdrv_child_try_set_aio_context(BlockDriverState *bs, AioContext *ctx,
+ BdrvChild *ignore_child, Error **errp)
+{
+ GSList *ignore;
+ bool ret;
+
+ ignore = ignore_child ? g_slist_prepend(NULL, ignore_child) : NULL;
+ ret = bdrv_can_set_aio_context(bs, ctx, &ignore, errp);
+ g_slist_free(ignore);
+
+ if (!ret) {
+ return -EPERM;
+ }
+
+ bdrv_set_aio_context(bs, ctx);
+ return 0;
+}
+
+int bdrv_try_set_aio_context(BlockDriverState *bs, AioContext *ctx,
+ Error **errp)
+{
+ return bdrv_child_try_set_aio_context(bs, ctx, NULL, errp);
+}
+
void bdrv_add_aio_context_notifier(BlockDriverState *bs,
void (*attached_aio_context)(AioContext *new_context, void *opaque),
void (*detach_aio_context)(void *opaque), void *opaque)