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bh=gpL/KtmpVIqThlM8BLmlN6PH2UjUT2DtdwR9cJu4xJs=; b=BEHR8HPACxRw0vGaUch4WSmnIX15wKmP6SmXex+4JxAhNACyHMSsqQVQXPhRmxDhvSR4S8 fv+RbyrtQ/bm8vKlavX8Ry+If1Ba3SgYHyjsq4lOG5/lDH/EL1V3paOssjHFeF8GAARw0G eFxZZANqBfF5hNv71k4nFXo9twDvRDY= X-MC-Unique: REorJkxLOeCmvFk5mNRDEw-1 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, stefanha@redhat.com, eesposit@redhat.com, eblake@redhat.com, pbonzini@redhat.com, vsementsov@yandex-team.ru, qemu-devel@nongnu.org Subject: [PATCH 15/24] block: Mark bdrv_replace_node_common() GRAPH_WRLOCK Date: Fri, 27 Oct 2023 17:53:24 +0200 Message-ID: <20231027155333.420094-16-kwolf@redhat.com> In-Reply-To: <20231027155333.420094-1-kwolf@redhat.com> References: <20231027155333.420094-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1698422086382100005 Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Eric Blake --- 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, } =20 /* + * 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=3Dtrue bdrv_replace_node_common skips updating from pare= nts * 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=3Dtrue @to must be in a backing chain of @from. I= n 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 **err= p) { Transaction *tran =3D tran_new(); g_autoptr(GSList) refresh_list =3D NULL; @@ -5433,16 +5435,9 @@ static int bdrv_replace_node_common(BlockDriverState= *from, =20 GLOBAL_STATE_CODE(); =20 - /* Make sure that @from doesn't go away until we have successfully att= ached - * all of its parents to @to. */ - bdrv_ref(from); - - assert(qemu_get_current_aio_context() =3D=3D qemu_get_aio_context()); + assert(from->quiesce_counter); + assert(to->quiesce_counter); assert(bdrv_get_aio_context(from) =3D=3D bdrv_get_aio_context(to)); - bdrv_drained_begin(from); - bdrv_drained_begin(to); - - bdrv_graph_wrlock(to); =20 if (detach_subchain) { assert(bdrv_chain_contains(from, to)); @@ -5483,33 +5478,51 @@ static int bdrv_replace_node_common(BlockDriverStat= e *from, =20 out: tran_finalize(tran, ret); - bdrv_graph_wrunlock(); - - bdrv_drained_end(to); - bdrv_drained_end(from); - bdrv_unref(from); - return ret; } =20 int bdrv_replace_node(BlockDriverState *from, BlockDriverState *to, Error **errp) { + int ret; + GLOBAL_STATE_CODE(); =20 - return bdrv_replace_node_common(from, to, true, false, errp); + /* Make sure that @from doesn't go away until we have successfully att= ached + * all of its parents to @to. */ + bdrv_ref(from); + bdrv_drained_begin(from); + bdrv_drained_begin(to); + bdrv_graph_wrlock(to); + + ret =3D 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; } =20 int bdrv_drop_filter(BlockDriverState *bs, Error **errp) { BlockDriverState *child_bs; + int ret; =20 GLOBAL_STATE_CODE(); + bdrv_graph_rdlock_main_loop(); child_bs =3D bdrv_filter_or_cow_bs(bs); bdrv_graph_rdunlock_main_loop(); =20 - return bdrv_replace_node_common(bs, child_bs, true, true, errp); + bdrv_drained_begin(child_bs); + bdrv_graph_wrlock(bs); + ret =3D bdrv_replace_node_common(bs, child_bs, true, true, errp); + bdrv_graph_wrunlock(); + bdrv_drained_end(child_bs); + + return ret; } =20 /* @@ -5957,15 +5970,15 @@ int bdrv_drop_intermediate(BlockDriverState *top, B= lockDriverState *base, =20 bdrv_ref(top); bdrv_drained_begin(base); - bdrv_graph_rdlock_main_loop(); + bdrv_graph_wrlock(base); =20 if (!top->drv || !base->drv) { - goto exit; + goto exit_wrlock; } =20 /* Make sure that base is in the backing chain of top */ if (!bdrv_chain_contains(top, base)) { - goto exit; + goto exit_wrlock; } =20 /* If 'base' recursively inherits from 'top' then we should set @@ -5997,6 +6010,8 @@ int bdrv_drop_intermediate(BlockDriverState *top, Blo= ckDriverState *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, Bl= ockDriverState *base, } =20 ret =3D 0; + goto exit; + +exit_wrlock: + bdrv_graph_wrunlock(); exit: - bdrv_graph_rdunlock_main_loop(); bdrv_drained_end(base); bdrv_unref(top); return ret; --=20 2.41.0