{"id":813555,"url":"http://patchwork.ozlabs.org/api/patches/813555/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20170913181910.29688-3-mreitz@redhat.com/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20170913181910.29688-3-mreitz@redhat.com>","list_archive_url":null,"date":"2017-09-13T18:18:54","name":"[02/18] block: BDS deletion during bdrv_drain_recurse","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"204fdfa4b7e478adc4adff5bf1cf4e3cce62bede","submitter":{"id":36836,"url":"http://patchwork.ozlabs.org/api/people/36836/?format=json","name":"Max Reitz","email":"mreitz@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20170913181910.29688-3-mreitz@redhat.com/mbox/","series":[{"id":2960,"url":"http://patchwork.ozlabs.org/api/series/2960/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=2960","date":"2017-09-13T18:18:52","name":"block/mirror: Add active-sync mirroring","version":1,"mbox":"http://patchwork.ozlabs.org/series/2960/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/813555/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/813555/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; helo=lists.gnu.org;\n\tenvelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n\treceiver=)","ext-mx07.extmail.prod.ext.phx2.redhat.com;\n\tdmarc=none (p=none dis=none) header.from=redhat.com","ext-mx07.extmail.prod.ext.phx2.redhat.com;\n\tspf=fail smtp.mailfrom=mreitz@redhat.com"],"Received":["from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11])\n\t(using TLSv1 with cipher AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby ozlabs.org (Postfix) with ESMTPS id 3xsqj226tjz9s7g\n\tfor ;\n\tThu, 14 Sep 2017 04:20:38 +1000 (AEST)","from localhost ([::1]:43983 helo=lists.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.71) (envelope-from\n\t)\n\tid 1dsCH6-0007n2-AM\n\tfor incoming@patchwork.ozlabs.org; Wed, 13 Sep 2017 14:20:36 -0400","from eggs.gnu.org ([2001:4830:134:3::10]:36470)\n\tby lists.gnu.org with esmtp (Exim 4.71)\n\t(envelope-from ) id 1dsCGE-0007jD-BK\n\tfor qemu-devel@nongnu.org; Wed, 13 Sep 2017 14:19:47 -0400","from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)\n\t(envelope-from ) id 1dsCGD-0004ia-3M\n\tfor qemu-devel@nongnu.org; Wed, 13 Sep 2017 14:19:42 -0400","from mx1.redhat.com ([209.132.183.28]:47724)\n\tby eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32)\n\t(Exim 4.71) (envelope-from )\n\tid 1dsCGA-0004gQ-CI; Wed, 13 Sep 2017 14:19:38 -0400","from smtp.corp.redhat.com\n\t(int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12])\n\t(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby mx1.redhat.com (Postfix) with ESMTPS id 7332CC04B924;\n\tWed, 13 Sep 2017 18:19:37 +0000 (UTC)","from localhost (ovpn-204-23.brq.redhat.com [10.40.204.23])\n\tby smtp.corp.redhat.com (Postfix) with ESMTPS id DB3BC60BE4;\n\tWed, 13 Sep 2017 18:19:29 +0000 (UTC)"],"DMARC-Filter":"OpenDMARC Filter v1.3.2 mx1.redhat.com 7332CC04B924","From":"Max Reitz ","To":"qemu-block@nongnu.org","Date":"Wed, 13 Sep 2017 20:18:54 +0200","Message-Id":"<20170913181910.29688-3-mreitz@redhat.com>","In-Reply-To":"<20170913181910.29688-1-mreitz@redhat.com>","References":"<20170913181910.29688-1-mreitz@redhat.com>","X-Scanned-By":"MIMEDefang 2.79 on 10.5.11.12","X-Greylist":"Sender IP whitelisted, not delayed by milter-greylist-4.5.16\n\t(mx1.redhat.com [10.5.110.31]);\n\tWed, 13 Sep 2017 18:19:37 +0000 (UTC)","X-detected-operating-system":"by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic]\n\t[fuzzy]","X-Received-From":"209.132.183.28","Subject":"[Qemu-devel] [PATCH 02/18] block: BDS deletion during\n\tbdrv_drain_recurse","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.21","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"Kevin Wolf , Fam Zheng ,\n\tqemu-devel@nongnu.org, Max Reitz ,\n\tStefan Hajnoczi , John Snow ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n\t"},"content":"Drainined a BDS child may lead to both the original BDS and/or its other\nchildren being deleted (e.g. if the original BDS represents a block\njob). We should prepare for this in both bdrv_drain_recurse() and\nbdrv_drained_begin() by monitoring whether the BDS we are about to drain\nstill exists at all.\n\nSigned-off-by: Max Reitz \n---\n block/io.c | 72 +++++++++++++++++++++++++++++++++++++++++++++-----------------\n 1 file changed, 52 insertions(+), 20 deletions(-)","diff":"diff --git a/block/io.c b/block/io.c\nindex 4378ae4c7d..8ec1a564ad 100644\n--- a/block/io.c\n+++ b/block/io.c\n@@ -182,33 +182,57 @@ static void bdrv_drain_invoke(BlockDriverState *bs)\n \n static bool bdrv_drain_recurse(BlockDriverState *bs)\n {\n- BdrvChild *child, *tmp;\n+ BdrvChild *child;\n bool waited;\n+ struct BDSToDrain {\n+ BlockDriverState *bs;\n+ BdrvDeletedStatus del_stat;\n+ QLIST_ENTRY(BDSToDrain) next;\n+ };\n+ QLIST_HEAD(, BDSToDrain) bs_list = QLIST_HEAD_INITIALIZER(bs_list);\n+ bool in_main_loop =\n+ qemu_get_current_aio_context() == qemu_get_aio_context();\n \n waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);\n \n /* Ensure any pending metadata writes are submitted to bs->file. */\n bdrv_drain_invoke(bs);\n \n- QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {\n- BlockDriverState *bs = child->bs;\n- bool in_main_loop =\n- qemu_get_current_aio_context() == qemu_get_aio_context();\n- assert(bs->refcnt > 0);\n- if (in_main_loop) {\n- /* In case the recursive bdrv_drain_recurse processes a\n- * block_job_defer_to_main_loop BH and modifies the graph,\n- * let's hold a reference to bs until we are done.\n- *\n- * IOThread doesn't have such a BH, and it is not safe to call\n- * bdrv_unref without BQL, so skip doing it there.\n- */\n- bdrv_ref(bs);\n- }\n- waited |= bdrv_drain_recurse(bs);\n- if (in_main_loop) {\n- bdrv_unref(bs);\n+ /* Draining children may result in other children being removed and maybe\n+ * even deleted, so copy the children list first */\n+ QLIST_FOREACH(child, &bs->children, next) {\n+ struct BDSToDrain *bs2d = g_new0(struct BDSToDrain, 1);\n+\n+ bs2d->bs = child->bs;\n+ QLIST_INSERT_HEAD(&bs->deleted_status, &bs2d->del_stat, next);\n+\n+ QLIST_INSERT_HEAD(&bs_list, bs2d, next);\n+ }\n+\n+ while (!QLIST_EMPTY(&bs_list)) {\n+ struct BDSToDrain *bs2d = QLIST_FIRST(&bs_list);\n+ QLIST_REMOVE(bs2d, next);\n+\n+ if (!bs2d->del_stat.deleted) {\n+ QLIST_REMOVE(&bs2d->del_stat, next);\n+\n+ if (in_main_loop) {\n+ /* In case the recursive bdrv_drain_recurse processes a\n+ * block_job_defer_to_main_loop BH and modifies the graph,\n+ * let's hold a reference to the BDS until we are done.\n+ *\n+ * IOThread doesn't have such a BH, and it is not safe to call\n+ * bdrv_unref without BQL, so skip doing it there.\n+ */\n+ bdrv_ref(bs2d->bs);\n+ }\n+ waited |= bdrv_drain_recurse(bs2d->bs);\n+ if (in_main_loop) {\n+ bdrv_unref(bs2d->bs);\n+ }\n }\n+\n+ g_free(bs2d);\n }\n \n return waited;\n@@ -252,17 +276,25 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs)\n \n void bdrv_drained_begin(BlockDriverState *bs)\n {\n+ BdrvDeletedStatus del_stat = { .deleted = false };\n+\n if (qemu_in_coroutine()) {\n bdrv_co_yield_to_drain(bs);\n return;\n }\n \n+ QLIST_INSERT_HEAD(&bs->deleted_status, &del_stat, next);\n+\n if (atomic_fetch_inc(&bs->quiesce_counter) == 0) {\n aio_disable_external(bdrv_get_aio_context(bs));\n bdrv_parent_drained_begin(bs);\n }\n \n- bdrv_drain_recurse(bs);\n+ if (!del_stat.deleted) {\n+ QLIST_REMOVE(&del_stat, next);\n+\n+ bdrv_drain_recurse(bs);\n+ }\n }\n \n void bdrv_drained_end(BlockDriverState *bs)\n","prefixes":["02/18"]}