On 17.09.2015 15:48, Kevin Wolf wrote:
> This simplifies the code somewhat, especially when dropping whole
> backing file subchains.
>
> The exception is the mirroring code that does adventurous things with
> bdrv_swap() and in order to keep it working, I had to duplicate most of
> bdrv_set_backing_hd() locally. We'll get rid again of this ugliness
> shortly.
>
> Signed-off-by: Kevin Wolf <kw...@redhat.com>
> ---
> block.c | 35 ++++++++++++++---------------------
> block/mirror.c | 17 ++++++++++++-----
> block/stream.c | 21 ---------------------
> block/vvfat.c | 6 +++++-
> include/block/block.h | 1 +
> 5 files changed, 32 insertions(+), 48 deletions(-)
>
> diff --git a/block.c b/block.c
> index fb94567..743f82e 100644
> --- a/block.c
> +++ b/block.c
> @@ -1094,7 +1094,7 @@ static BdrvChild *bdrv_attach_child(BlockDriverState
> *parent_bs,
> return child;
> }
>
> -static void bdrv_detach_child(BdrvChild *child)
> +void bdrv_detach_child(BdrvChild *child)
> {
> QLIST_REMOVE(child, next);
> g_free(child);
> @@ -1112,13 +1112,20 @@ void bdrv_unref_child(BlockDriverState *parent,
> BdrvChild *child)
> bdrv_unref(child_bs);
> }
>
> +/*
> + * Sets the backing file 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)
> {
> + if (backing_hd) {
> + bdrv_ref(backing_hd);
> + }
>
> if (bs->backing) {
> assert(bs->backing_blocker);
> bdrv_op_unblock_all(bs->backing->bs, bs->backing_blocker);
> - bdrv_detach_child(bs->backing);
> + bdrv_unref_child(bs, bs->backing);
> } else if (backing_hd) {
> error_setg(&bs->backing_blocker,
> "node is used as backing hd of '%s'",
> @@ -1214,7 +1221,10 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict
> *options, Error **errp)
> goto free_exit;
> }
>
> + /* Hook up the backing file link; drop our reference, bs owns the
> + * backing_hd reference now */
> bdrv_set_backing_hd(bs, backing_hd);
> + bdrv_unref(backing_hd);
>
> free_exit:
> g_free(backing_filename);
> @@ -1884,11 +1894,7 @@ void bdrv_close(BlockDriverState *bs)
>
> bs->drv->bdrv_close(bs);
>
> - if (bs->backing) {
> - BlockDriverState *backing_hd = bs->backing->bs;
> - bdrv_set_backing_hd(bs, NULL);
> - bdrv_unref(backing_hd);
> - }
> + bdrv_set_backing_hd(bs, NULL);
>
> if (bs->file != NULL) {
> bdrv_unref(bs->file->bs);
> @@ -2427,12 +2433,9 @@ int bdrv_drop_intermediate(BlockDriverState *active,
> BlockDriverState *top,
> BlockDriverState *intermediate;
> BlockDriverState *base_bs = NULL;
> BlockDriverState *new_top_bs = NULL;
> - BlkIntermediateStates *intermediate_state, *next;
> + BlkIntermediateStates *intermediate_state;
> int ret = -EIO;
>
> - QSIMPLEQ_HEAD(states_to_delete, BlkIntermediateStates) states_to_delete;
> - QSIMPLEQ_INIT(&states_to_delete);
> -
> if (!top->drv || !base->drv) {
> goto exit;
> }
> @@ -2459,7 +2462,6 @@ int bdrv_drop_intermediate(BlockDriverState *active,
> BlockDriverState *top,
> while (intermediate) {
> intermediate_state = g_new0(BlkIntermediateStates, 1);
> intermediate_state->bs = intermediate;
> - QSIMPLEQ_INSERT_TAIL(&states_to_delete, intermediate_state, entry);
>
> if (backing_bs(intermediate) == base) {
> base_bs = backing_bs(intermediate);
> @@ -2482,17 +2484,8 @@ int bdrv_drop_intermediate(BlockDriverState *active,
> BlockDriverState *top,
> }
> bdrv_set_backing_hd(new_top_bs, base_bs);
>
> - QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry,
> next) {
> - /* so that bdrv_close() does not recursively close the chain */
> - bdrv_set_backing_hd(intermediate_state->bs, NULL);
> - bdrv_unref(intermediate_state->bs);
> - }
> ret = 0;
> -
> exit:
> - QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry,
> next) {
> - g_free(intermediate_state);
> - }
> return ret;
> }
>
To me that begs the question why before we didn't simply
bdrv_ref(base_bs), and then bdrv_unref(top). Well, now it's even
simpler, so that's good.
> diff --git a/block/mirror.c b/block/mirror.c
> index 259e11a..571da27 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -370,11 +370,18 @@ static void mirror_exit(BlockJob *job, void *opaque)
> bdrv_swap(s->target, to_replace);
> if (s->common.driver->job_type == BLOCK_JOB_TYPE_COMMIT) {
> /* drop the bs loop chain formed by the swap: break the loop then
> - * trigger the unref from the top one */
> - BlockDriverState *p = s->base->backing
> - ? s->base->backing->bs : NULL;
> - bdrv_set_backing_hd(s->base, NULL);
> - bdrv_unref(p);
> + * trigger the unref */
> + /* FIXME This duplicates bdrv_set_backing_hd(), except for the
> + * actual detach/unref so that the loop can be broken. When
> + * bdrv_swap() gets replaced, this will become sane again. */
> + BlockDriverState *backing = s->base->backing->bs;
> + assert(s->base->backing_blocker);
> + bdrv_op_unblock_all(s->base->backing->bs,
> s->base->backing_blocker);
I know it's dropped later on anwyay, but I can't stop my fingers from
suggesting s/s->base->backing->bs/backing/.
Anyway, with or without that:
Reviewed-by: Max Reitz <mre...@redhat.com>
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