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block: Implement .(can_)set_aio_ctx for BlockBackend

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bdrv_try_set_aio_context() currently fails if a BlockBackend is attached
to a node because it doesn't implement the BdrvChildRole callbacks for
AioContext management.

We can allow changing the AioContext of monitor-owned BlockBackends as
long as no device is attached to them.

When setting the AioContext of the root node of a BlockBackend, we now
need to pass blk->root as an ignored child because we don't want the
root node to recursively call back into BlockBackend and execute
blk_do_set_aio_context() a second time.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2019-05-06 19:18:01 +02:00
parent 7e2f096a82
commit 38475269d4
1 changed files with 43 additions and 2 deletions
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45
block/block-backend.c
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@ -124,6 +124,11 @@ static void blk_root_drained_end(BdrvChild *child);
static void blk_root_change_media(BdrvChild *child, bool load); static void blk_root_change_media(BdrvChild *child, bool load);
static void blk_root_resize(BdrvChild *child); static void blk_root_resize(BdrvChild *child);
static bool blk_root_can_set_aio_ctx(BdrvChild *child, AioContext *ctx,
GSList **ignore, Error **errp);
static void blk_root_set_aio_ctx(BdrvChild *child, AioContext *ctx,
GSList **ignore);
static char *blk_root_get_parent_desc(BdrvChild *child) static char *blk_root_get_parent_desc(BdrvChild *child)
{ {
BlockBackend *blk = child->opaque; BlockBackend *blk = child->opaque;
@ -300,6 +305,9 @@ static const BdrvChildRole child_root = {
.attach = blk_root_attach, .attach = blk_root_attach,
.detach = blk_root_detach, .detach = blk_root_detach,
.can_set_aio_ctx = blk_root_can_set_aio_ctx,
.set_aio_ctx = blk_root_set_aio_ctx,
}; };
/* /*
@ -1852,7 +1860,8 @@ static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb)
return blk_get_aio_context(blk_acb->blk); return blk_get_aio_context(blk_acb->blk);
} }
void blk_set_aio_context(BlockBackend *blk, AioContext *new_context) static void blk_do_set_aio_context(BlockBackend *blk, AioContext *new_context,
bool update_root_node)
{ {
BlockDriverState *bs = blk_bs(blk); BlockDriverState *bs = blk_bs(blk);
ThrottleGroupMember *tgm = &blk->public.throttle_group_member; ThrottleGroupMember *tgm = &blk->public.throttle_group_member;
@ -1864,10 +1873,42 @@ void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)
throttle_group_attach_aio_context(tgm, new_context); throttle_group_attach_aio_context(tgm, new_context);
bdrv_drained_end(bs); bdrv_drained_end(bs);
} }
bdrv_set_aio_context(bs, new_context); if (update_root_node) {
GSList *ignore = g_slist_prepend(NULL, blk->root);
bdrv_set_aio_context_ignore(bs, new_context, &ignore);
g_slist_free(ignore);
}
} }
} }
void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)
{
blk_do_set_aio_context(blk, new_context, true);
}
static bool blk_root_can_set_aio_ctx(BdrvChild *child, AioContext *ctx,
GSList **ignore, Error **errp)
{
BlockBackend *blk = child->opaque;
/* Only manually created BlockBackends that are not attached to anything
* can change their AioContext without updating their user. */
if (!blk->name || blk->dev) {
/* TODO Add BB name/QOM path */
error_setg(errp, "Cannot change iothread of active block backend");
return false;
}
return true;
}
static void blk_root_set_aio_ctx(BdrvChild *child, AioContext *ctx,
GSList **ignore)
{
BlockBackend *blk = child->opaque;
blk_do_set_aio_context(blk, ctx, false);
}
void blk_add_aio_context_notifier(BlockBackend *blk, void blk_add_aio_context_notifier(BlockBackend *blk,
void (*attached_aio_context)(AioContext *new_context, void *opaque), void (*attached_aio_context)(AioContext *new_context, void *opaque),
void (*detach_aio_context)(void *opaque), void *opaque) void (*detach_aio_context)(void *opaque), void *opaque)