[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PATCH 08/22] block: Take graph rdlock in parts of reopen
From: |
Kevin Wolf |
Subject: |
[PATCH 08/22] block: Take graph rdlock in parts of reopen |
Date: |
Fri, 29 Sep 2023 16:51:43 +0200 |
Reopen isn't easy with respect to locking because many of its functions
need to iterate the graph, some change it, and then you get some drains
in the middle where you can't hold any locks.
Therefore just documents most of the functions to be unlocked, and take
locks internally before accessing the graph.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
include/block/block_int-common.h | 13 +++++---
block.c | 57 ++++++++++++++++++++------------
2 files changed, 43 insertions(+), 27 deletions(-)
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 29c5b8a3c5..0373cbed49 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -235,11 +235,14 @@ struct BlockDriver {
Error **errp);
/* For handling image reopen for split or non-split files. */
- int (*bdrv_reopen_prepare)(BDRVReopenState *reopen_state,
- BlockReopenQueue *queue, Error **errp);
- void (*bdrv_reopen_commit)(BDRVReopenState *reopen_state);
- void (*bdrv_reopen_commit_post)(BDRVReopenState *reopen_state);
- void (*bdrv_reopen_abort)(BDRVReopenState *reopen_state);
+ int GRAPH_UNLOCKED_PTR (*bdrv_reopen_prepare)(
+ BDRVReopenState *reopen_state, BlockReopenQueue *queue, Error **errp);
+ void GRAPH_UNLOCKED_PTR (*bdrv_reopen_commit)(
+ BDRVReopenState *reopen_state);
+ void GRAPH_UNLOCKED_PTR (*bdrv_reopen_commit_post)(
+ BDRVReopenState *reopen_state);
+ void GRAPH_UNLOCKED_PTR (*bdrv_reopen_abort)(
+ BDRVReopenState *reopen_state);
void (*bdrv_join_options)(QDict *options, QDict *old_options);
int GRAPH_UNLOCKED_PTR (*bdrv_open)(
diff --git a/block.c b/block.c
index fb494f4a8b..4c4fab3579 100644
--- a/block.c
+++ b/block.c
@@ -4313,8 +4313,8 @@ static int bdrv_reset_options_allowed(BlockDriverState
*bs,
/*
* Returns true if @child can be reached recursively from @bs
*/
-static bool bdrv_recurse_has_child(BlockDriverState *bs,
- BlockDriverState *child)
+static bool GRAPH_RDLOCK
+bdrv_recurse_has_child(BlockDriverState *bs, BlockDriverState *child)
{
BdrvChild *c;
@@ -4355,15 +4355,12 @@ static bool bdrv_recurse_has_child(BlockDriverState *bs,
*
* To be called with bs->aio_context locked.
*/
-static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
- BlockDriverState *bs,
- QDict *options,
- const BdrvChildClass *klass,
- BdrvChildRole role,
- bool parent_is_format,
- QDict *parent_options,
- int parent_flags,
- bool keep_old_opts)
+static BlockReopenQueue * GRAPH_RDLOCK
+bdrv_reopen_queue_child(BlockReopenQueue *bs_queue, BlockDriverState *bs,
+ QDict *options, const BdrvChildClass *klass,
+ BdrvChildRole role, bool parent_is_format,
+ QDict *parent_options, int parent_flags,
+ bool keep_old_opts)
{
assert(bs != NULL);
@@ -4375,6 +4372,11 @@ static BlockReopenQueue
*bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
GLOBAL_STATE_CODE();
+ /*
+ * Strictly speaking, draining is illegal under GRAPH_RDLOCK. We know that
+ * we've been called with bdrv_graph_rdlock_main_loop(), though, so it's ok
+ * in practice.
+ */
bdrv_drained_begin(bs);
if (bs_queue == NULL) {
@@ -4516,6 +4518,7 @@ BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue
*bs_queue,
QDict *options, bool keep_old_opts)
{
GLOBAL_STATE_CODE();
+ GRAPH_RDLOCK_GUARD_MAINLOOP();
return bdrv_reopen_queue_child(bs_queue, bs, options, NULL, 0, false,
NULL, 0, keep_old_opts);
@@ -4735,9 +4738,10 @@ int bdrv_reopen_set_read_only(BlockDriverState *bs, bool
read_only,
* Callers must make sure that their AioContext locking is still correct after
* this.
*/
-static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
- bool is_backing, Transaction
*tran,
- Error **errp)
+static int GRAPH_UNLOCKED
+bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
+ bool is_backing, Transaction *tran,
+ Error **errp)
{
BlockDriverState *bs = reopen_state->bs;
BlockDriverState *new_child_bs;
@@ -4747,6 +4751,7 @@ static int
bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
QObject *value;
const char *str;
AioContext *ctx, *old_ctx;
+ bool has_child;
int ret;
GLOBAL_STATE_CODE();
@@ -4766,7 +4771,13 @@ static int
bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
new_child_bs = bdrv_lookup_bs(NULL, str, errp);
if (new_child_bs == NULL) {
return -EINVAL;
- } else if (bdrv_recurse_has_child(new_child_bs, bs)) {
+ }
+
+ bdrv_graph_rdlock_main_loop();
+ has_child = bdrv_recurse_has_child(new_child_bs, bs);
+ bdrv_graph_rdunlock_main_loop();
+
+ if (has_child) {
error_setg(errp, "Making '%s' a %s child of '%s' would create a "
"cycle", str, child_name, bs->node_name);
return -EINVAL;
@@ -4865,9 +4876,9 @@ static int
bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
* After calling this function, the transaction @change_child_tran may only be
* completed while holding a writer lock for the graph.
*/
-static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
- BlockReopenQueue *queue,
- Transaction *change_child_tran, Error **errp)
+static int GRAPH_UNLOCKED
+bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
+ Transaction *change_child_tran, Error **errp)
{
int ret = -1;
int old_flags;
@@ -5009,6 +5020,8 @@ static int bdrv_reopen_prepare(BDRVReopenState
*reopen_state,
if (qdict_size(reopen_state->options)) {
const QDictEntry *entry = qdict_first(reopen_state->options);
+ GRAPH_RDLOCK_GUARD_MAINLOOP();
+
do {
QObject *new = entry->value;
QObject *old = qdict_get(reopen_state->bs->options, entry->key);
@@ -5082,7 +5095,7 @@ error:
* makes them final by swapping the staging BlockDriverState contents into
* the active BlockDriverState contents.
*/
-static void bdrv_reopen_commit(BDRVReopenState *reopen_state)
+static void GRAPH_UNLOCKED bdrv_reopen_commit(BDRVReopenState *reopen_state)
{
BlockDriver *drv;
BlockDriverState *bs;
@@ -5099,6 +5112,8 @@ static void bdrv_reopen_commit(BDRVReopenState
*reopen_state)
drv->bdrv_reopen_commit(reopen_state);
}
+ GRAPH_RDLOCK_GUARD_MAINLOOP();
+
/* set BDS specific flags now */
qobject_unref(bs->explicit_options);
qobject_unref(bs->options);
@@ -5120,9 +5135,7 @@ static void bdrv_reopen_commit(BDRVReopenState
*reopen_state)
qdict_del(bs->explicit_options, "backing");
qdict_del(bs->options, "backing");
- bdrv_graph_rdlock_main_loop();
bdrv_refresh_limits(bs, NULL, NULL);
- bdrv_graph_rdunlock_main_loop();
bdrv_refresh_total_sectors(bs, bs->total_sectors);
}
@@ -5130,7 +5143,7 @@ static void bdrv_reopen_commit(BDRVReopenState
*reopen_state)
* Abort the reopen, and delete and free the staged changes in
* reopen_state
*/
-static void bdrv_reopen_abort(BDRVReopenState *reopen_state)
+static void GRAPH_UNLOCKED bdrv_reopen_abort(BDRVReopenState *reopen_state)
{
BlockDriver *drv;
--
2.41.0
- [PATCH 00/22] block: Graph locking part 5 (protect children/parent links), Kevin Wolf, 2023/09/29
- [PATCH 03/22] block: Take graph rdlock in bdrv_inactivate_all(), Kevin Wolf, 2023/09/29
- [PATCH 02/22] block-coroutine-wrapper: Add no_co_wrapper_bdrv_rdlock functions, Kevin Wolf, 2023/09/29
- [PATCH 01/22] test-bdrv-drain: Don't call bdrv_graph_wrlock() in coroutine context, Kevin Wolf, 2023/09/29
- [PATCH 04/22] block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 06/22] block: Mark bdrv_parent_cb_resize() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 05/22] block: Mark drain related functions GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 09/22] block: Mark bdrv_get_xdbg_block_graph() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 08/22] block: Take graph rdlock in parts of reopen,
Kevin Wolf <=
- [PATCH 10/22] block: Mark bdrv_refresh_filename() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 11/22] block: Mark bdrv_primary_child() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 12/22] block: Mark bdrv_get_parent_name() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 07/22] block: Mark bdrv_snapshot_fallback() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 13/22] block: Mark bdrv_amend_options() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 14/22] qcow2: Mark qcow2_signal_corruption() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 15/22] qcow2: Mark qcow2_inactivate() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 17/22] block: Mark bdrv_op_is_blocked() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 16/22] qcow2: Mark check_constraints_on_bitmap() GRAPH_RDLOCK, Kevin Wolf, 2023/09/29
- [PATCH 19/22] block: Mark bdrv_get_specific_info() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/09/29