From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 41C16C77B73 for ; Tue, 30 May 2023 16:38:20 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q42IC-0007k8-76; Tue, 30 May 2023 12:33:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q42HH-0006Nx-1h for qemu-devel@nongnu.org; Tue, 30 May 2023 12:33:00 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q42HF-0008EG-Al for qemu-devel@nongnu.org; Tue, 30 May 2023 12:32:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685464372; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TFmwsZj7mEJbuyFquMgG1tFmHr+v8B1z2+1WMORARnM=; b=MsHmyt6PoIoK3i+z13x24S2c1xR2fTe74DyvudYnh5uPr2IlxYLIfv1zR8+bSdcW+nEoOv jcxQRPj43q4I2fRGbS8yTXjfDBiuXCtgdkGHl8J4Ck1Cz2U41CD1Ujc/2zwosFCay9n2IG auJALeGjToBHpRLYvbzRicqR9JIeN64= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-52-uU_9FGYmM8qmmJBrz1Jazg-1; Tue, 30 May 2023 12:32:51 -0400 X-MC-Unique: uU_9FGYmM8qmmJBrz1Jazg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D2246185A78F; Tue, 30 May 2023 16:32:50 +0000 (UTC) Received: from merkur.redhat.com (unknown [10.39.194.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id 22482C154D2; Tue, 30 May 2023 16:32:50 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, richard.henderson@linaro.org, qemu-devel@nongnu.org Subject: [PULL 04/32] block-backend: Fix blk_new_open() for iothreads Date: Tue, 30 May 2023 18:32:11 +0200 Message-Id: <20230530163239.576632-5-kwolf@redhat.com> In-Reply-To: <20230530163239.576632-1-kwolf@redhat.com> References: <20230530163239.576632-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.167, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org This fixes blk_new_open() to not assume that bs is in the main context. In particular, the BlockBackend must be created with the right AioContext because it will refuse to move to a different context afterwards. (blk->allow_aio_context_change is false.) Use this opportunity to use blk_insert_bs() instead of duplicating the bdrv_root_attach_child() call. This is consistent with what blk_new_with_bs() does. Add comments to document the locking rules. Signed-off-by: Kevin Wolf Message-Id: <20230525124713.401149-5-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/block-backend.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) diff --git a/block/block-backend.c b/block/block-backend.c index 1d89fabd35..dde60e0f71 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -389,6 +389,8 @@ BlockBackend *blk_new(AioContext *ctx, uint64_t perm, uint64_t shared_perm) * Both sets of permissions can be changed later using blk_set_perm(). * * Return the new BlockBackend on success, null on failure. + * + * Callers must hold the AioContext lock of @bs. */ BlockBackend *blk_new_with_bs(BlockDriverState *bs, uint64_t perm, uint64_t shared_perm, Error **errp) @@ -406,11 +408,15 @@ BlockBackend *blk_new_with_bs(BlockDriverState *bs, uint64_t perm, /* * Creates a new BlockBackend, opens a new BlockDriverState, and connects both. - * The new BlockBackend is in the main AioContext. + * By default, the new BlockBackend is in the main AioContext, but if the + * parameters connect it with any existing node in a different AioContext, it + * may end up there instead. * * Just as with bdrv_open(), after having called this function the reference to * @options belongs to the block layer (even on failure). * + * Called without holding an AioContext lock. + * * TODO: Remove @filename and @flags; it should be possible to specify a whole * BDS tree just by specifying the @options QDict (or @reference, * alternatively). At the time of adding this function, this is not possible, @@ -422,6 +428,7 @@ BlockBackend *blk_new_open(const char *filename, const char *reference, { BlockBackend *blk; BlockDriverState *bs; + AioContext *ctx; uint64_t perm = 0; uint64_t shared = BLK_PERM_ALL; @@ -451,18 +458,24 @@ BlockBackend *blk_new_open(const char *filename, const char *reference, shared = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED; } - blk = blk_new(qemu_get_aio_context(), perm, shared); aio_context_acquire(qemu_get_aio_context()); bs = bdrv_open(filename, reference, options, flags, errp); aio_context_release(qemu_get_aio_context()); if (!bs) { - blk_unref(blk); return NULL; } - blk->root = bdrv_root_attach_child(bs, "root", &child_root, - BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, - perm, shared, blk, errp); + /* bdrv_open() could have moved bs to a different AioContext */ + ctx = bdrv_get_aio_context(bs); + blk = blk_new(bdrv_get_aio_context(bs), perm, shared); + blk->perm = perm; + blk->shared_perm = shared; + + aio_context_acquire(ctx); + blk_insert_bs(blk, bs, errp); + bdrv_unref(bs); + aio_context_release(ctx); + if (!blk->root) { blk_unref(blk); return NULL; @@ -903,6 +916,8 @@ void blk_remove_bs(BlockBackend *blk) /* * Associates a new BlockDriverState with @blk. + * + * Callers must hold the AioContext lock of @bs. */ int blk_insert_bs(BlockBackend *blk, BlockDriverState *bs, Error **errp) { -- 2.40.1