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From: Kevin Wolf <kwolf@redhat.com>
To: qemu-block@nongnu.org
Cc: kwolf@redhat.com,
qemu-devel@nongnu.org
Subject: [PULL 08/28] block: Mark bdrv_replace_child_noperm() GRAPH_WRLOCK
Date: Fri, 15 Sep 2023 16:43:24 +0200
Message-ID: <20230915144344.238596-9-kwolf@redhat.com>
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Instead of taking the writer lock internally, require callers to already
hold it when calling bdrv_replace_child_noperm(). 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: <20230911094620.45040-9-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block.c | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git a/block.c b/block.c
index c8ac7cfac4..61856f5c33 100644
--- a/block.c
+++ b/block.c
@@ -91,8 +91,9 @@ static BlockDriverState *bdrv_open_inherit(const char *fi=
lename,
static bool bdrv_recurse_has_child(BlockDriverState *bs,
BlockDriverState *child);
=20
-static void bdrv_replace_child_noperm(BdrvChild *child,
- BlockDriverState *new_bs);
+static void GRAPH_WRLOCK
+bdrv_replace_child_noperm(BdrvChild *child, BlockDriverState *new_bs);
+
static void bdrv_remove_child(BdrvChild *child, Transaction *tran);
=20
static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
@@ -2387,6 +2388,8 @@ static void bdrv_replace_child_abort(void *opaque)
BlockDriverState *new_bs =3D s->child->bs;
=20
GLOBAL_STATE_CODE();
+ bdrv_graph_wrlock(s->old_bs);
+
/* old_bs reference is transparently moved from @s to @s->child */
if (!s->child->bs) {
/*
@@ -2403,6 +2406,8 @@ static void bdrv_replace_child_abort(void *opaque)
}
assert(s->child->quiesced_parent);
bdrv_replace_child_noperm(s->child, s->old_bs);
+
+ bdrv_graph_wrunlock();
bdrv_unref(new_bs);
}
=20
@@ -2439,7 +2444,10 @@ static void bdrv_replace_child_tran(BdrvChild *child=
, BlockDriverState *new_bs,
if (new_bs) {
bdrv_ref(new_bs);
}
+
+ bdrv_graph_wrlock(new_bs);
bdrv_replace_child_noperm(child, new_bs);
+ bdrv_graph_wrunlock();
/* old_bs reference is transparently moved from @child to @s */
}
=20
@@ -2858,8 +2866,8 @@ uint64_t bdrv_qapi_perm_to_blk_perm(BlockPermission q=
api_perm)
* If @new_bs is non-NULL, the parent of @child must already be drained th=
rough
* @child and the caller must hold the AioContext lock for @new_bs.
*/
-static void bdrv_replace_child_noperm(BdrvChild *child,
- BlockDriverState *new_bs)
+static void GRAPH_WRLOCK
+bdrv_replace_child_noperm(BdrvChild *child, BlockDriverState *new_bs)
{
BlockDriverState *old_bs =3D child->bs;
int new_bs_quiesce_counter;
@@ -2894,8 +2902,6 @@ static void bdrv_replace_child_noperm(BdrvChild *chil=
d,
assert(bdrv_get_aio_context(old_bs) =3D=3D bdrv_get_aio_context(ne=
w_bs));
}
=20
- /* TODO Pull this up into the callers to avoid polling here */
- bdrv_graph_wrlock(new_bs);
if (old_bs) {
if (child->klass->detach) {
child->klass->detach(child);
@@ -2911,7 +2917,6 @@ static void bdrv_replace_child_noperm(BdrvChild *chil=
d,
child->klass->attach(child);
}
}
- bdrv_graph_wrunlock();
=20
/*
* If the parent was drained through this BdrvChild previously, but ne=
w_bs
@@ -2952,7 +2957,10 @@ static void bdrv_attach_child_common_abort(void *opa=
que)
BlockDriverState *bs =3D s->child->bs;
=20
GLOBAL_STATE_CODE();
+
+ bdrv_graph_wrlock(NULL);
bdrv_replace_child_noperm(s->child, NULL);
+ bdrv_graph_wrunlock();
=20
if (bdrv_get_aio_context(bs) !=3D s->old_child_ctx) {
bdrv_try_change_aio_context(bs, s->old_child_ctx, NULL, &error_abo=
rt);
@@ -3080,8 +3088,10 @@ static BdrvChild *bdrv_attach_child_common(BlockDriv=
erState *child_bs,
* a problem, we already did this), but it will still poll until the p=
arent
* is fully quiesced, so it will not be negatively affected either.
*/
+ bdrv_graph_wrlock(child_bs);
bdrv_parent_drained_begin_single(new_child);
bdrv_replace_child_noperm(new_child, child_bs);
+ bdrv_graph_wrunlock();
=20
BdrvAttachChildCommonState *s =3D g_new(BdrvAttachChildCommonState, 1);
*s =3D (BdrvAttachChildCommonState) {
@@ -3225,7 +3235,9 @@ void bdrv_root_unref_child(BdrvChild *child)
BlockDriverState *child_bs =3D child->bs;
=20
GLOBAL_STATE_CODE();
+ bdrv_graph_wrlock(NULL);
bdrv_replace_child_noperm(child, NULL);
+ bdrv_graph_wrunlock();
bdrv_child_free(child);
=20
if (child_bs) {
--=20
2.41.0