[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PULL 04/39] block: bdrv_append(): don't consume reference
From: |
Kevin Wolf |
Subject: |
[PULL 04/39] block: bdrv_append(): don't consume reference |
Date: |
Fri, 30 Apr 2021 12:51:12 +0200 |
From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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>
Message-Id: <20210428151804.439460-5-vsementsov@virtuozzo.com>
Signed-off-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);
}
--
2.30.2
- [PULL 00/39] Block layer patches, Kevin Wolf, 2021/04/30
- [PULL 01/39] tests/test-bdrv-graph-mod: add test_parallel_exclusive_write, Kevin Wolf, 2021/04/30
- [PULL 02/39] tests/test-bdrv-graph-mod: add test_parallel_perm_update, Kevin Wolf, 2021/04/30
- [PULL 04/39] block: bdrv_append(): don't consume reference,
Kevin Wolf <=
- [PULL 03/39] tests/test-bdrv-graph-mod: add test_append_greedy_filter, Kevin Wolf, 2021/04/30
- [PULL 06/39] block: drop ctx argument from bdrv_root_attach_child, Kevin Wolf, 2021/04/30
- [PULL 05/39] block: BdrvChildClass: add .get_parent_aio_context handler, Kevin Wolf, 2021/04/30
- [PULL 07/39] block: make bdrv_reopen_{prepare,commit,abort} private, Kevin Wolf, 2021/04/30
- [PULL 08/39] util: add transactions.c, Kevin Wolf, 2021/04/30
- [PULL 09/39] block: bdrv_refresh_perms: check for parents permissions conflict, Kevin Wolf, 2021/04/30
- [PULL 11/39] block: rewrite bdrv_child_try_set_perm() using bdrv_refresh_perms(), Kevin Wolf, 2021/04/30
- [PULL 10/39] block: refactor bdrv_child* permission functions, Kevin Wolf, 2021/04/30
- [PULL 12/39] block: inline bdrv_child_*() permission functions calls, Kevin Wolf, 2021/04/30
- [PULL 13/39] block: use topological sort for permission update, Kevin Wolf, 2021/04/30