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[PATCH v4 04/36] block: bdrv_append(): don't consume reference
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[PATCH v4 04/36] block: bdrv_append(): don't consume reference |
Date: |
Wed, 28 Apr 2021 18:17:32 +0300 |
We have too much comments for this feature. It seems better just don't
do it. Most of real users (tests don't count) have to create additional
reference.
Drop also comment in external_snapshot_prepare:
- bdrv_append doesn't "remove" old bs in common sense, it sounds
strange
- the fact that bdrv_append can fail is obvious from the context
- the fact that we must rollback all changes in transaction abort is
known (it's the direct role of abort)
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
---
block.c | 25 +++----------------------
block/backup-top.c | 1 -
block/commit.c | 1 +
block/mirror.c | 3 ---
blockdev.c | 4 ----
tests/unit/test-bdrv-drain.c | 2 +-
tests/unit/test-bdrv-graph-mod.c | 3 +++
7 files changed, 8 insertions(+), 31 deletions(-)
diff --git a/block.c b/block.c
index c5b887cec1..1e7e8907e4 100644
--- a/block.c
+++ b/block.c
@@ -3213,11 +3213,6 @@ static BlockDriverState
*bdrv_append_temp_snapshot(BlockDriverState *bs,
goto out;
}
- /* bdrv_append() consumes a strong reference to bs_snapshot
- * (i.e. it will call bdrv_unref() on it) even on error, so in
- * order to be able to return one, we have to increase
- * bs_snapshot's refcount here */
- bdrv_ref(bs_snapshot);
ret = bdrv_append(bs_snapshot, bs, errp);
if (ret < 0) {
bs_snapshot = NULL;
@@ -4679,36 +4674,22 @@ int bdrv_replace_node(BlockDriverState *from,
BlockDriverState *to,
* bs_new must not be attached to a BlockBackend.
*
* This function does not create any image files.
- *
- * bdrv_append() takes ownership of a bs_new reference and unrefs it because
- * that's what the callers commonly need. bs_new will be referenced by the old
- * parents of bs_top after bdrv_append() returns. If the caller needs to keep a
- * reference of its own, it must call bdrv_ref().
*/
int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
Error **errp)
{
int ret = bdrv_set_backing_hd(bs_new, bs_top, errp);
if (ret < 0) {
- goto out;
+ return ret;
}
ret = bdrv_replace_node(bs_top, bs_new, errp);
if (ret < 0) {
bdrv_set_backing_hd(bs_new, NULL, &error_abort);
- goto out;
+ return ret;
}
- ret = 0;
-
-out:
- /*
- * bs_new is now referenced by its new parents, we don't need the
- * additional reference any more.
- */
- bdrv_unref(bs_new);
-
- return ret;
+ return 0;
}
static void bdrv_delete(BlockDriverState *bs)
diff --git a/block/backup-top.c b/block/backup-top.c
index 589e8b651d..62d09f213e 100644
--- a/block/backup-top.c
+++ b/block/backup-top.c
@@ -234,7 +234,6 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState
*source,
bdrv_drained_begin(source);
- bdrv_ref(top);
ret = bdrv_append(top, source, errp);
if (ret < 0) {
error_prepend(errp, "Cannot append backup-top filter: ");
diff --git a/block/commit.c b/block/commit.c
index dd9ba87349..b89bb20b75 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -312,6 +312,7 @@ void commit_start(const char *job_id, BlockDriverState *bs,
commit_top_bs->total_sectors = top->total_sectors;
ret = bdrv_append(commit_top_bs, top, errp);
+ bdrv_unref(commit_top_bs); /* referenced by new parents or failed */
if (ret < 0) {
commit_top_bs = NULL;
goto fail;
diff --git a/block/mirror.c b/block/mirror.c
index 5a71bd8bbc..840b8e8c15 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1630,9 +1630,6 @@ static BlockJob *mirror_start_job(
bs_opaque->is_commit = target_is_backing;
- /* bdrv_append takes ownership of the mirror_top_bs reference, need to keep
- * it alive until block_job_create() succeeds even if bs has no parent. */
- bdrv_ref(mirror_top_bs);
bdrv_drained_begin(bs);
ret = bdrv_append(mirror_top_bs, bs, errp);
bdrv_drained_end(bs);
diff --git a/blockdev.c b/blockdev.c
index a57590aae4..834c2304a1 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1576,10 +1576,6 @@ static void external_snapshot_prepare(BlkActionState
*common,
goto out;
}
- /* This removes our old bs and adds the new bs. This is an operation that
- * can fail, so we need to do it in .prepare; undoing it for abort is
- * always possible. */
- bdrv_ref(state->new_bs);
ret = bdrv_append(state->new_bs, state->old_bs, errp);
if (ret < 0) {
goto out;
diff --git a/tests/unit/test-bdrv-drain.c b/tests/unit/test-bdrv-drain.c
index 8a29e33e00..892f7f47d8 100644
--- a/tests/unit/test-bdrv-drain.c
+++ b/tests/unit/test-bdrv-drain.c
@@ -1478,7 +1478,6 @@ static void test_append_to_drained(void)
g_assert_cmpint(base_s->drain_count, ==, 1);
g_assert_cmpint(base->in_flight, ==, 0);
- /* Takes ownership of overlay, so we don't have to unref it later */
bdrv_append(overlay, base, &error_abort);
g_assert_cmpint(base->in_flight, ==, 0);
g_assert_cmpint(overlay->in_flight, ==, 0);
@@ -1495,6 +1494,7 @@ static void test_append_to_drained(void)
g_assert_cmpint(overlay->quiesce_counter, ==, 0);
g_assert_cmpint(overlay_s->drain_count, ==, 0);
+ bdrv_unref(overlay);
bdrv_unref(base);
blk_unref(blk);
}
diff --git a/tests/unit/test-bdrv-graph-mod.c b/tests/unit/test-bdrv-graph-mod.c
index 5b6934e68b..a6064b1863 100644
--- a/tests/unit/test-bdrv-graph-mod.c
+++ b/tests/unit/test-bdrv-graph-mod.c
@@ -138,6 +138,7 @@ static void test_update_perm_tree(void)
ret = bdrv_append(filter, bs, NULL);
g_assert_cmpint(ret, <, 0);
+ bdrv_unref(filter);
blk_unref(root);
}
@@ -202,6 +203,7 @@ static void test_should_update_child(void)
bdrv_append(filter, bs, &error_abort);
g_assert(target->backing->bs == bs);
+ bdrv_unref(filter);
bdrv_unref(bs);
blk_unref(root);
}
@@ -380,6 +382,7 @@ static void test_append_greedy_filter(void)
&error_abort);
bdrv_append(fl, base, &error_abort);
+ bdrv_unref(fl);
bdrv_unref(top);
}
--
2.29.2
- [PATCH v4 03/36] tests/test-bdrv-graph-mod: add test_append_greedy_filter, (continued)
- [PATCH v4 03/36] tests/test-bdrv-graph-mod: add test_append_greedy_filter, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 02/36] tests/test-bdrv-graph-mod: add test_parallel_perm_update, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 05/36] block: BdrvChildClass: add .get_parent_aio_context handler, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 14/36] block: add bdrv_drv_set_perm transaction action, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 06/36] block: drop ctx argument from bdrv_root_attach_child, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 16/36] block: add bdrv_replace_child_safe() transaction action, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 15/36] block: add bdrv_list_* permission update functions, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 08/36] util: add transactions.c, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 17/36] block: fix bdrv_replace_node_common, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 18/36] block: add bdrv_attach_child_common() transaction action, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 04/36] block: bdrv_append(): don't consume reference,
Vladimir Sementsov-Ogievskiy <=
- [PATCH v4 09/36] block: bdrv_refresh_perms: check for parents permissions conflict, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 07/36] block: make bdrv_reopen_{prepare, commit, abort} private, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 10/36] block: refactor bdrv_child* permission functions, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 11/36] block: rewrite bdrv_child_try_set_perm() using bdrv_refresh_perms(), Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 21/36] block: adapt bdrv_append() for inserting filters, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 22/36] block: add bdrv_remove_filter_or_cow transaction action, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 19/36] block: add bdrv_attach_child_noperm() transaction action, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 31/36] block: drop unused permission update functions, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 24/36] block/backup-top: drop .active, Vladimir Sementsov-Ogievskiy, 2021/04/28
- [PATCH v4 20/36] block: split out bdrv_replace_node_noperm(), Vladimir Sementsov-Ogievskiy, 2021/04/28