From patchwork Wed Jul 31 12:32:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 13748657 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 826CCC49EA1 for ; Wed, 31 Jul 2024 12:32:59 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sZ8VU-0002Tw-1Q; Wed, 31 Jul 2024 08:32:40 -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 1sZ8VQ-0002In-WB for qemu-devel@nongnu.org; Wed, 31 Jul 2024 08:32:37 -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 1sZ8VO-000477-Hw for qemu-devel@nongnu.org; Wed, 31 Jul 2024 08:32:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722429154; 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=7fWS/MeBs6Kai+qgd4zCs2xGsxcdZvo3lCYuqY77YaM=; b=SSEMbtTANmO+zieKSnRiNfJ/CJS2D0C49GB2D0B1Cwo9aTH816tYaf7A5mZgAWMN2s/rnq NeKX2MhYo3mnS2+BJw+kQSj7ogw7G9OqamLFs6s1yhuh1iPPPvdABVbudpFufNZjJiFoUW 55O5jDI/Nx6d0j6F3vGt/MGsZ/CLjxo= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-322-OS34m-dmMaWE102R_yoDtg-1; Wed, 31 Jul 2024 08:32:29 -0400 X-MC-Unique: OS34m-dmMaWE102R_yoDtg-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 935D818B649A; Wed, 31 Jul 2024 12:32:28 +0000 (UTC) Received: from merkur.redhat.com (unknown [10.39.194.1]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 107F51955F65; Wed, 31 Jul 2024 12:32:25 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, pbonzini@redhat.com, fam@euphon.net, stefanha@redhat.com, qemu-devel@nongnu.org Subject: [PATCH v2 3/4] scsi-disk: Add warning comments that host_status errors take a shortcut Date: Wed, 31 Jul 2024 14:32:06 +0200 Message-ID: <20240731123207.27636-4-kwolf@redhat.com> In-Reply-To: <20240731123207.27636-1-kwolf@redhat.com> References: <20240731123207.27636-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.126, 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=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 scsi_block_sgio_complete() has surprising behaviour in that there are error cases in which it directly completes the request and never calls the passed callback. In the current state of the code, this doesn't seem to result in bugs, but with future code changes, we must be careful to never rely on the callback doing some cleanup until this code smell is fixed. For now, just add warnings to make people aware of the trap. Signed-off-by: Kevin Wolf --- hw/scsi/scsi-disk.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c index 6e1a5c98df..69a195177e 100644 --- a/hw/scsi/scsi-disk.c +++ b/hw/scsi/scsi-disk.c @@ -68,6 +68,9 @@ struct SCSIDiskClass { /* * Callbacks receive ret == 0 for success. Errors are represented either as * negative errno values, or as positive SAM status codes. + * + * Beware: For errors returned in host_status, the function may directly + * complete the request and never call the callback. */ DMAIOFunc *dma_readv; DMAIOFunc *dma_writev; @@ -381,6 +384,7 @@ done: scsi_req_unref(&r->req); } +/* May not be called in all error cases, don't rely on cleanup here */ static void scsi_dma_complete(void *opaque, int ret) { SCSIDiskReq *r = (SCSIDiskReq *)opaque; @@ -421,6 +425,7 @@ done: scsi_req_unref(&r->req); } +/* May not be called in all error cases, don't rely on cleanup here */ static void scsi_read_complete(void *opaque, int ret) { SCSIDiskReq *r = (SCSIDiskReq *)opaque; @@ -560,6 +565,7 @@ done: scsi_req_unref(&r->req); } +/* May not be called in all error cases, don't rely on cleanup here */ static void scsi_write_complete(void * opaque, int ret) { SCSIDiskReq *r = (SCSIDiskReq *)opaque; @@ -2821,6 +2827,7 @@ static void scsi_block_sgio_complete(void *opaque, int ret) sg_io_hdr_t *io_hdr = &req->io_header; if (ret == 0) { + /* FIXME This skips calling req->cb() and any cleanup in it */ if (io_hdr->host_status != SCSI_HOST_OK) { scsi_req_complete_failed(&r->req, io_hdr->host_status); scsi_req_unref(&r->req);