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block: Mark bdrv_attach_child() GRAPH_WRLOCK
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Instead of taking the writer lock internally, require callers to already
hold it when calling bdrv_attach_child_common(). These callers will
typically already hold the graph lock once the locking work is
completed, which means that they can't call functions that take it
internally.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230911094620.45040-13-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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@kevmw
kevmw committed Sep 20, 2023
1 parent 5661a00 commit afdaeb9
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Showing 6 changed files with 43 additions and 10 deletions.
7 changes: 3 additions & 4 deletions block.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3219,8 +3219,6 @@ BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,

GLOBAL_STATE_CODE();

bdrv_graph_wrlock(child_bs);

child = bdrv_attach_child_noperm(parent_bs, child_bs, child_name,
child_class, child_role, tran, errp);
if (!child) {
Expand All @@ -3235,9 +3233,8 @@ BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,

out:
tran_finalize(tran, ret);
bdrv_graph_wrunlock();

bdrv_unref(child_bs);
bdrv_schedule_unref(child_bs);

return ret < 0 ? NULL : child;
}
Expand Down Expand Up @@ -3758,11 +3755,13 @@ BdrvChild *bdrv_open_child(const char *filename,
return NULL;
}

bdrv_graph_wrlock(NULL);
ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
errp);
aio_context_release(ctx);
bdrv_graph_wrunlock();

return child;
}
Expand Down
2 changes: 2 additions & 0 deletions block/quorum.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1094,8 +1094,10 @@ static void quorum_add_child(BlockDriverState *bs, BlockDriverState *child_bs,
/* We can safely add the child now */
bdrv_ref(child_bs);

bdrv_graph_wrlock(child_bs);
child = bdrv_attach_child(bs, child_bs, indexstr, &child_of_bds,
BDRV_CHILD_DATA, errp);
bdrv_graph_wrunlock();
if (child == NULL) {
s->next_child_index--;
goto out;
Expand Down
6 changes: 6 additions & 0 deletions block/replication.c
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Original file line number Diff line number Diff line change
Expand Up @@ -542,12 +542,15 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
return;
}

bdrv_graph_wrlock(bs);

bdrv_ref(hidden_disk->bs);
s->hidden_disk = bdrv_attach_child(bs, hidden_disk->bs, "hidden disk",
&child_of_bds, BDRV_CHILD_DATA,
&local_err);
if (local_err) {
error_propagate(errp, local_err);
bdrv_graph_wrunlock();
aio_context_release(aio_context);
return;
}
Expand All @@ -558,10 +561,13 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
BDRV_CHILD_DATA, &local_err);
if (local_err) {
error_propagate(errp, local_err);
bdrv_graph_wrunlock();
aio_context_release(aio_context);
return;
}

bdrv_graph_wrunlock();

/* start backup job now */
error_setg(&s->blocker,
"Block device is in use by internal backup job");
Expand Down
14 changes: 8 additions & 6 deletions include/block/block-global-state.h
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Original file line number Diff line number Diff line change
Expand Up @@ -226,12 +226,14 @@ void no_coroutine_fn bdrv_unref(BlockDriverState *bs);
void coroutine_fn no_co_wrapper bdrv_co_unref(BlockDriverState *bs);
void GRAPH_WRLOCK bdrv_schedule_unref(BlockDriverState *bs);
void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child);
BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
BlockDriverState *child_bs,
const char *child_name,
const BdrvChildClass *child_class,
BdrvChildRole child_role,
Error **errp);

BdrvChild * GRAPH_WRLOCK
bdrv_attach_child(BlockDriverState *parent_bs,
BlockDriverState *child_bs,
const char *child_name,
const BdrvChildClass *child_class,
BdrvChildRole child_role,
Error **errp);

bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp);
void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason);
Expand Down
14 changes: 14 additions & 0 deletions tests/unit/test-bdrv-drain.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1055,26 +1055,32 @@ static void do_test_delete_by_drain(bool detach_instead_of_delete,

null_bs = bdrv_open("null-co://", NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
&error_abort);
bdrv_graph_wrlock(NULL);
bdrv_attach_child(bs, null_bs, "null-child", &child_of_bds,
BDRV_CHILD_DATA, &error_abort);
bdrv_graph_wrunlock();

/* This child will be the one to pass to requests through to, and
* it will stall until a drain occurs */
child_bs = bdrv_new_open_driver(&bdrv_test, "child", BDRV_O_RDWR,
&error_abort);
child_bs->total_sectors = 65536 >> BDRV_SECTOR_BITS;
/* Takes our reference to child_bs */
bdrv_graph_wrlock(NULL);
tts->wait_child = bdrv_attach_child(bs, child_bs, "wait-child",
&child_of_bds,
BDRV_CHILD_DATA | BDRV_CHILD_PRIMARY,
&error_abort);
bdrv_graph_wrunlock();

/* This child is just there to be deleted
* (for detach_instead_of_delete == true) */
null_bs = bdrv_open("null-co://", NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
&error_abort);
bdrv_graph_wrlock(NULL);
bdrv_attach_child(bs, null_bs, "null-child", &child_of_bds, BDRV_CHILD_DATA,
&error_abort);
bdrv_graph_wrunlock();

blk = blk_new(qemu_get_aio_context(), BLK_PERM_ALL, BLK_PERM_ALL);
blk_insert_bs(blk, bs, &error_abort);
Expand Down Expand Up @@ -1159,9 +1165,11 @@ static void detach_indirect_bh(void *opaque)
bdrv_unref_child(data->parent_b, data->child_b);

bdrv_ref(data->c);
bdrv_graph_wrlock(NULL);
data->child_c = bdrv_attach_child(data->parent_b, data->c, "PB-C",
&child_of_bds, BDRV_CHILD_DATA,
&error_abort);
bdrv_graph_wrunlock();
}

static void detach_by_parent_aio_cb(void *opaque, int ret)
Expand Down Expand Up @@ -1258,6 +1266,7 @@ static void test_detach_indirect(bool by_parent_cb)
/* Set child relationships */
bdrv_ref(b);
bdrv_ref(a);
bdrv_graph_wrlock(NULL);
child_b = bdrv_attach_child(parent_b, b, "PB-B", &child_of_bds,
BDRV_CHILD_DATA, &error_abort);
child_a = bdrv_attach_child(parent_b, a, "PB-A", &child_of_bds,
Expand All @@ -1267,6 +1276,7 @@ static void test_detach_indirect(bool by_parent_cb)
bdrv_attach_child(parent_a, a, "PA-A",
by_parent_cb ? &child_of_bds : &detach_by_driver_cb_class,
BDRV_CHILD_DATA, &error_abort);
bdrv_graph_wrunlock();

g_assert_cmpint(parent_a->refcnt, ==, 1);
g_assert_cmpint(parent_b->refcnt, ==, 1);
Expand Down Expand Up @@ -1685,13 +1695,15 @@ static void test_drop_intermediate_poll(void)
* Establish the chain last, so the chain links are the first
* elements in the BDS.parents lists
*/
bdrv_graph_wrlock(NULL);
for (i = 0; i < 3; i++) {
if (i) {
/* Takes the reference to chain[i - 1] */
bdrv_attach_child(chain[i], chain[i - 1], "chain",
&chain_child_class, BDRV_CHILD_COW, &error_abort);
}
}
bdrv_graph_wrunlock();

job = block_job_create("job", &test_simple_job_driver, NULL, job_node,
0, BLK_PERM_ALL, 0, 0, NULL, NULL, &error_abort);
Expand Down Expand Up @@ -1936,8 +1948,10 @@ static void do_test_replace_child_mid_drain(int old_drain_count,
new_child_bs->total_sectors = 1;

bdrv_ref(old_child_bs);
bdrv_graph_wrlock(NULL);
bdrv_attach_child(parent_bs, old_child_bs, "child", &child_of_bds,
BDRV_CHILD_COW, &error_abort);
bdrv_graph_wrunlock();
parent_s->setup_completed = true;

for (i = 0; i < old_drain_count; i++) {
Expand Down
10 changes: 10 additions & 0 deletions tests/unit/test-bdrv-graph-mod.c
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Original file line number Diff line number Diff line change
Expand Up @@ -137,8 +137,10 @@ static void test_update_perm_tree(void)

blk_insert_bs(root, bs, &error_abort);

bdrv_graph_wrlock(NULL);
bdrv_attach_child(filter, bs, "child", &child_of_bds,
BDRV_CHILD_DATA, &error_abort);
bdrv_graph_wrunlock();

aio_context_acquire(qemu_get_aio_context());
ret = bdrv_append(filter, bs, NULL);
Expand Down Expand Up @@ -205,8 +207,10 @@ static void test_should_update_child(void)
bdrv_set_backing_hd(target, bs, &error_abort);

g_assert(target->backing->bs == bs);
bdrv_graph_wrlock(NULL);
bdrv_attach_child(filter, target, "target", &child_of_bds,
BDRV_CHILD_DATA, &error_abort);
bdrv_graph_wrunlock();
aio_context_acquire(qemu_get_aio_context());
bdrv_append(filter, bs, &error_abort);
aio_context_release(qemu_get_aio_context());
Expand Down Expand Up @@ -236,6 +240,7 @@ static void test_parallel_exclusive_write(void)
*/
bdrv_ref(base);

bdrv_graph_wrlock(NULL);
bdrv_attach_child(top, fl1, "backing", &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
&error_abort);
Expand All @@ -245,6 +250,7 @@ static void test_parallel_exclusive_write(void)
bdrv_attach_child(fl2, base, "backing", &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
&error_abort);
bdrv_graph_wrunlock();

bdrv_replace_node(fl1, fl2, &error_abort);

Expand Down Expand Up @@ -349,6 +355,7 @@ static void test_parallel_perm_update(void)
*/
bdrv_ref(base);

bdrv_graph_wrlock(NULL);
bdrv_attach_child(top, ws, "file", &child_of_bds, BDRV_CHILD_DATA,
&error_abort);
c_fl1 = bdrv_attach_child(ws, fl1, "first", &child_of_bds,
Expand All @@ -361,6 +368,7 @@ static void test_parallel_perm_update(void)
bdrv_attach_child(fl2, base, "backing", &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
&error_abort);
bdrv_graph_wrunlock();

/* Select fl1 as first child to be active */
s->selected = c_fl1;
Expand Down Expand Up @@ -410,9 +418,11 @@ static void test_append_greedy_filter(void)
BlockDriverState *base = no_perm_node("base");
BlockDriverState *fl = exclusive_writer_node("fl1");

bdrv_graph_wrlock(NULL);
bdrv_attach_child(top, base, "backing", &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
&error_abort);
bdrv_graph_wrunlock();

aio_context_acquire(qemu_get_aio_context());
bdrv_append(fl, base, &error_abort);
Expand Down

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