From patchwork Tue May 28 19:28:41 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Max Reitz X-Patchwork-Id: 10965745 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5FF88933 for ; Tue, 28 May 2019 19:44:19 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 503E126E49 for ; Tue, 28 May 2019 19:44:19 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 40BE22867C; Tue, 28 May 2019 19:44:19 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 9735D26E49 for ; Tue, 28 May 2019 19:44:18 +0000 (UTC) Received: from localhost ([127.0.0.1]:41716 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVi1B-0004bo-Sg for patchwork-qemu-devel@patchwork.kernel.org; Tue, 28 May 2019 15:44:17 -0400 Received: from eggs.gnu.org ([209.51.188.92]:37047) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVhoB-0001dl-7D for qemu-devel@nongnu.org; Tue, 28 May 2019 15:30:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hVho6-000244-E4 for qemu-devel@nongnu.org; Tue, 28 May 2019 15:30:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36580) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hVhns-0000vy-0z; Tue, 28 May 2019 15:30:33 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7BC267E424; Tue, 28 May 2019 19:29:31 +0000 (UTC) Received: from localhost (unknown [10.40.205.223]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1363D10027C2; Tue, 28 May 2019 19:29:29 +0000 (UTC) From: Max Reitz To: qemu-block@nongnu.org Date: Tue, 28 May 2019 21:28:41 +0200 Message-Id: <20190528192847.2730-16-mreitz@redhat.com> In-Reply-To: <20190528192847.2730-1-mreitz@redhat.com> References: <20190528192847.2730-1-mreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Tue, 28 May 2019 19:29:37 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 15/21] block: Make bdrv_root_attach_child() unref child_bs on failure X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Peter Maydell , qemu-devel@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Alberto Garcia A consequence of the previous patch is that bdrv_attach_child() transfers the reference to child_bs from the caller to parent_bs, which will drop it on bdrv_close() or when someone calls bdrv_unref_child(). But this only happens when bdrv_attach_child() succeeds. If it fails then the caller is responsible for dropping the reference to child_bs. This patch makes bdrv_attach_child() take the reference also when there is an error, freeing the caller for having to do it. A similar situation happens with bdrv_root_attach_child(), so the changes on this patch affect both functions. Signed-off-by: Alberto Garcia Message-id: 20dfb3d9ccec559cdd1a9690146abad5d204a186.1557754872.git.berto@igalia.com [mreitz: Removed now superfluous BdrvChild * variable in bdrv_open_child()] Signed-off-by: Max Reitz --- block.c | 30 ++++++++++++++++++------------ block/block-backend.c | 3 +-- block/quorum.c | 1 - blockjob.c | 2 +- 4 files changed, 20 insertions(+), 16 deletions(-) diff --git a/block.c b/block.c index be37280dc7..1a73e310c1 100644 --- a/block.c +++ b/block.c @@ -2243,6 +2243,13 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs) } } +/* + * This function steals the reference to child_bs from the caller. + * That reference is later dropped by bdrv_root_unref_child(). + * + * On failure NULL is returned, errp is set and the reference to + * child_bs is also dropped. + */ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs, const char *child_name, const BdrvChildRole *child_role, @@ -2255,6 +2262,7 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs, ret = bdrv_check_update_perm(child_bs, NULL, perm, shared_perm, NULL, errp); if (ret < 0) { bdrv_abort_perm_update(child_bs); + bdrv_unref(child_bs); return NULL; } @@ -2274,6 +2282,14 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs, return child; } +/* + * This function transfers the reference to child_bs from the caller + * to parent_bs. That reference is later dropped by parent_bs on + * bdrv_close() or if someone calls bdrv_unref_child(). + * + * On failure NULL is returned, errp is set and the reference to + * child_bs is also dropped. + */ BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs, BlockDriverState *child_bs, const char *child_name, @@ -2401,12 +2417,9 @@ void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd, /* If backing_hd was already part of bs's backing chain, and * inherits_from pointed recursively to bs then let's update it to * point directly to bs (else it will become NULL). */ - if (update_inherits_from) { + if (bs->backing && update_inherits_from) { backing_hd->inherits_from = bs; } - if (!bs->backing) { - bdrv_unref(backing_hd); - } out: bdrv_refresh_limits(bs, NULL); @@ -2594,7 +2607,6 @@ BdrvChild *bdrv_open_child(const char *filename, const BdrvChildRole *child_role, bool allow_none, Error **errp) { - BdrvChild *c; BlockDriverState *bs; bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_role, @@ -2603,13 +2615,7 @@ BdrvChild *bdrv_open_child(const char *filename, return NULL; } - c = bdrv_attach_child(parent, bs, bdref_key, child_role, errp); - if (!c) { - bdrv_unref(bs); - return NULL; - } - - return c; + return bdrv_attach_child(parent, bs, bdref_key, child_role, errp); } /* TODO Future callers may need to specify parent/child_role in order for diff --git a/block/block-backend.c b/block/block-backend.c index 4c0a8ef88d..ad3e1c882d 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -392,7 +392,6 @@ BlockBackend *blk_new_open(const char *filename, const char *reference, blk->root = bdrv_root_attach_child(bs, "root", &child_root, perm, BLK_PERM_ALL, blk, errp); if (!blk->root) { - bdrv_unref(bs); blk_unref(blk); return NULL; } @@ -800,12 +799,12 @@ void blk_remove_bs(BlockBackend *blk) int blk_insert_bs(BlockBackend *blk, BlockDriverState *bs, Error **errp) { ThrottleGroupMember *tgm = &blk->public.throttle_group_member; + bdrv_ref(bs); blk->root = bdrv_root_attach_child(bs, "root", &child_root, blk->perm, blk->shared_perm, blk, errp); if (blk->root == NULL) { return -EPERM; } - bdrv_ref(bs); notifier_list_notify(&blk->insert_bs_notifiers, blk); if (tgm->throttle_state) { diff --git a/block/quorum.c b/block/quorum.c index 352f729136..133ee18204 100644 --- a/block/quorum.c +++ b/block/quorum.c @@ -1019,7 +1019,6 @@ static void quorum_add_child(BlockDriverState *bs, BlockDriverState *child_bs, child = bdrv_attach_child(bs, child_bs, indexstr, &child_format, errp); if (child == NULL) { s->next_child_index--; - bdrv_unref(child_bs); goto out; } s->children = g_renew(BdrvChild *, s->children, s->num_children + 1); diff --git a/blockjob.c b/blockjob.c index 9ca942ba01..cc5f18e7cd 100644 --- a/blockjob.c +++ b/blockjob.c @@ -204,6 +204,7 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs, { BdrvChild *c; + bdrv_ref(bs); c = bdrv_root_attach_child(bs, name, &child_job, perm, shared_perm, job, errp); if (c == NULL) { @@ -211,7 +212,6 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs, } job->nodes = g_slist_prepend(job->nodes, c); - bdrv_ref(bs); bdrv_op_block_all(bs, job->blocker); return 0;