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[PATCH 15/24] block: Mark bdrv_replace_node_common() GRAPH_WRLOCK
From: |
Kevin Wolf |
Subject: |
[PATCH 15/24] block: Mark bdrv_replace_node_common() GRAPH_WRLOCK |
Date: |
Fri, 27 Oct 2023 17:53:24 +0200 |
Instead of taking the writer lock internally, require callers to already
hold it when calling bdrv_replace_node_common(). Basically everthing in
the function needs the lock and its callers may already want to hold the
graph lock and so wouldn't be able to call functions that take it
internally.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block.c | 68 ++++++++++++++++++++++++++++++++++++---------------------
1 file changed, 43 insertions(+), 25 deletions(-)
diff --git a/block.c b/block.c
index dc43e36f69..c7409cf658 100644
--- a/block.c
+++ b/block.c
@@ -5412,6 +5412,9 @@ bdrv_replace_node_noperm(BlockDriverState *from,
}
/*
+ * Switch all parents of @from to point to @to instead. @from and @to must be
in
+ * the same AioContext and both must be drained.
+ *
* With auto_skip=true bdrv_replace_node_common skips updating from parents
* if it creates a parent-child relation loop or if parent is block-job.
*
@@ -5421,10 +5424,9 @@ bdrv_replace_node_noperm(BlockDriverState *from,
* With @detach_subchain=true @to must be in a backing chain of @from. In this
* case backing link of the cow-parent of @to is removed.
*/
-static int bdrv_replace_node_common(BlockDriverState *from,
- BlockDriverState *to,
- bool auto_skip, bool detach_subchain,
- Error **errp)
+static int GRAPH_WRLOCK
+bdrv_replace_node_common(BlockDriverState *from, BlockDriverState *to,
+ bool auto_skip, bool detach_subchain, Error **errp)
{
Transaction *tran = tran_new();
g_autoptr(GSList) refresh_list = NULL;
@@ -5433,16 +5435,9 @@ static int bdrv_replace_node_common(BlockDriverState
*from,
GLOBAL_STATE_CODE();
- /* Make sure that @from doesn't go away until we have successfully attached
- * all of its parents to @to. */
- bdrv_ref(from);
-
- assert(qemu_get_current_aio_context() == qemu_get_aio_context());
+ assert(from->quiesce_counter);
+ assert(to->quiesce_counter);
assert(bdrv_get_aio_context(from) == bdrv_get_aio_context(to));
- bdrv_drained_begin(from);
- bdrv_drained_begin(to);
-
- bdrv_graph_wrlock(to);
if (detach_subchain) {
assert(bdrv_chain_contains(from, to));
@@ -5483,33 +5478,51 @@ static int bdrv_replace_node_common(BlockDriverState
*from,
out:
tran_finalize(tran, ret);
- bdrv_graph_wrunlock();
-
- bdrv_drained_end(to);
- bdrv_drained_end(from);
- bdrv_unref(from);
-
return ret;
}
int bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
Error **errp)
{
+ int ret;
+
GLOBAL_STATE_CODE();
- return bdrv_replace_node_common(from, to, true, false, errp);
+ /* Make sure that @from doesn't go away until we have successfully attached
+ * all of its parents to @to. */
+ bdrv_ref(from);
+ bdrv_drained_begin(from);
+ bdrv_drained_begin(to);
+ bdrv_graph_wrlock(to);
+
+ ret = bdrv_replace_node_common(from, to, true, false, errp);
+
+ bdrv_graph_wrunlock();
+ bdrv_drained_end(to);
+ bdrv_drained_end(from);
+ bdrv_unref(from);
+
+ return ret;
}
int bdrv_drop_filter(BlockDriverState *bs, Error **errp)
{
BlockDriverState *child_bs;
+ int ret;
GLOBAL_STATE_CODE();
+
bdrv_graph_rdlock_main_loop();
child_bs = bdrv_filter_or_cow_bs(bs);
bdrv_graph_rdunlock_main_loop();
- return bdrv_replace_node_common(bs, child_bs, true, true, errp);
+ bdrv_drained_begin(child_bs);
+ bdrv_graph_wrlock(bs);
+ ret = bdrv_replace_node_common(bs, child_bs, true, true, errp);
+ bdrv_graph_wrunlock();
+ bdrv_drained_end(child_bs);
+
+ return ret;
}
/*
@@ -5957,15 +5970,15 @@ int bdrv_drop_intermediate(BlockDriverState *top,
BlockDriverState *base,
bdrv_ref(top);
bdrv_drained_begin(base);
- bdrv_graph_rdlock_main_loop();
+ bdrv_graph_wrlock(base);
if (!top->drv || !base->drv) {
- goto exit;
+ goto exit_wrlock;
}
/* Make sure that base is in the backing chain of top */
if (!bdrv_chain_contains(top, base)) {
- goto exit;
+ goto exit_wrlock;
}
/* If 'base' recursively inherits from 'top' then we should set
@@ -5997,6 +6010,8 @@ int bdrv_drop_intermediate(BlockDriverState *top,
BlockDriverState *base,
* That's a FIXME.
*/
bdrv_replace_node_common(top, base, false, false, &local_err);
+ bdrv_graph_wrunlock();
+
if (local_err) {
error_report_err(local_err);
goto exit;
@@ -6029,8 +6044,11 @@ int bdrv_drop_intermediate(BlockDriverState *top,
BlockDriverState *base,
}
ret = 0;
+ goto exit;
+
+exit_wrlock:
+ bdrv_graph_wrunlock();
exit:
- bdrv_graph_rdunlock_main_loop();
bdrv_drained_end(base);
bdrv_unref(top);
return ret;
--
2.41.0
- [PATCH 11/24] block: Mark bdrv_filter_child() and callers GRAPH_RDLOCK, (continued)
- [PATCH 11/24] block: Mark bdrv_filter_child() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/10/27
- [PATCH 10/24] block: Mark bdrv_chain_contains() and callers GRAPH_RDLOCK, Kevin Wolf, 2023/10/27
- [PATCH 04/24] block: Mark bdrv_root_attach_child() GRAPH_WRLOCK, Kevin Wolf, 2023/10/27
- [PATCH 14/24] block: Inline bdrv_set_backing_noperm(), Kevin Wolf, 2023/10/27
- [PATCH 16/24] block: Mark bdrv_replace_node() GRAPH_WRLOCK, Kevin Wolf, 2023/10/27
- [PATCH 15/24] block: Mark bdrv_replace_node_common() GRAPH_WRLOCK,
Kevin Wolf <=
- [PATCH 18/24] blkverify: Add locking for request_fn, Kevin Wolf, 2023/10/27
- [PATCH 22/24] vhdx: Take locks for accessing bs->file, Kevin Wolf, 2023/10/27
- [PATCH 21/24] qcow2: Take locks for accessing bs->file, Kevin Wolf, 2023/10/27
- [PATCH 23/24] block: Take graph lock for most of .bdrv_open, Kevin Wolf, 2023/10/27
- [PATCH 19/24] block: Introduce bdrv_co_change_backing_file(), Kevin Wolf, 2023/10/27