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 72F55C7EE23 for ; Tue, 30 May 2023 16:35:43 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q42IF-0008MD-VC; Tue, 30 May 2023 12:33:56 -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 1q42Hf-0006ua-H9 for qemu-devel@nongnu.org; Tue, 30 May 2023 12:33:20 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q42Hc-0008TD-Nh for qemu-devel@nongnu.org; Tue, 30 May 2023 12:33:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685464395; 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=sM8CqCJfymg0LztUUAinTRoTzulNqxCG6biluR1gPT8=; b=CWR1HKsWXdOULtMf75LCOxIzw2A3VUU94L+Umq244mHV8zSm5pQeYmwEmsJifyGbtDwzPF bdvzhQqT03hefRzoaS9Av3kcpiGM0wSz7CgpdFYpMw1uMTDPUXGb6g8Lx14CETu6jahd9Y 1UN0LSNAXp24kPFc7lsPUACX6ezuscs= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-561-eSBDAEjZNGC-hrRCvwfl-w-1; Tue, 30 May 2023 12:33:11 -0400 X-MC-Unique: eSBDAEjZNGC-hrRCvwfl-w-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 D06AE3C025C6; Tue, 30 May 2023 16:33:10 +0000 (UTC) Received: from merkur.redhat.com (unknown [10.39.194.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id 228C6C154D2; Tue, 30 May 2023 16:33:10 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, richard.henderson@linaro.org, qemu-devel@nongnu.org Subject: [PULL 25/32] block/export: rewrite vduse-blk drain code Date: Tue, 30 May 2023 18:32:32 +0200 Message-Id: <20230530163239.576632-26-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=170.10.129.124; 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=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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Stefan Hajnoczi vduse_blk_detach_ctx() waits for in-flight requests using AIO_WAIT_WHILE(). This is not allowed according to a comment in bdrv_set_aio_context_commit(): /* * Take the old AioContex when detaching it from bs. * At this point, new_context lock is already acquired, and we are now * also taking old_context. This is safe as long as bdrv_detach_aio_context * does not call AIO_POLL_WHILE(). */ Use this opportunity to rewrite the drain code in vduse-blk: - Use the BlockExport refcount so that vduse_blk_exp_delete() is only called when there are no more requests in flight. - Implement .drained_poll() so in-flight request coroutines are stopped by the time .bdrv_detach_aio_context() is called. - Remove AIO_WAIT_WHILE() from vduse_blk_detach_ctx() to solve the .bdrv_detach_aio_context() constraint violation. It's no longer needed due to the previous changes. - Always handle the VDUSE file descriptor, even in drained sections. The VDUSE file descriptor doesn't submit I/O, so it's safe to handle it in drained sections. This ensures that the VDUSE kernel code gets a fast response. - Suspend virtqueue fd handlers in .drained_begin() and resume them in .drained_end(). This eliminates the need for the aio_set_fd_handler(is_external=true) flag, which is being removed from QEMU. This is a long list but splitting it into individual commits would probably lead to git bisect failures - the changes are all related. Signed-off-by: Stefan Hajnoczi Reviewed-by: Kevin Wolf Message-Id: <20230516190238.8401-14-stefanha@redhat.com> Signed-off-by: Kevin Wolf --- block/export/vduse-blk.c | 132 +++++++++++++++++++++++++++------------ 1 file changed, 93 insertions(+), 39 deletions(-) diff --git a/block/export/vduse-blk.c b/block/export/vduse-blk.c index b53ef39da0..a25556fe04 100644 --- a/block/export/vduse-blk.c +++ b/block/export/vduse-blk.c @@ -31,7 +31,8 @@ typedef struct VduseBlkExport { VduseDev *dev; uint16_t num_queues; char *recon_file; - unsigned int inflight; + unsigned int inflight; /* atomic */ + bool vqs_started; } VduseBlkExport; typedef struct VduseBlkReq { @@ -41,13 +42,24 @@ typedef struct VduseBlkReq { static void vduse_blk_inflight_inc(VduseBlkExport *vblk_exp) { - vblk_exp->inflight++; + if (qatomic_fetch_inc(&vblk_exp->inflight) == 0) { + /* Prevent export from being deleted */ + aio_context_acquire(vblk_exp->export.ctx); + blk_exp_ref(&vblk_exp->export); + aio_context_release(vblk_exp->export.ctx); + } } static void vduse_blk_inflight_dec(VduseBlkExport *vblk_exp) { - if (--vblk_exp->inflight == 0) { + if (qatomic_fetch_dec(&vblk_exp->inflight) == 1) { + /* Wake AIO_WAIT_WHILE() */ aio_wait_kick(); + + /* Now the export can be deleted */ + aio_context_acquire(vblk_exp->export.ctx); + blk_exp_unref(&vblk_exp->export); + aio_context_release(vblk_exp->export.ctx); } } @@ -124,8 +136,12 @@ static void vduse_blk_enable_queue(VduseDev *dev, VduseVirtq *vq) { VduseBlkExport *vblk_exp = vduse_dev_get_priv(dev); + if (!vblk_exp->vqs_started) { + return; /* vduse_blk_drained_end() will start vqs later */ + } + aio_set_fd_handler(vblk_exp->export.ctx, vduse_queue_get_fd(vq), - true, on_vduse_vq_kick, NULL, NULL, NULL, vq); + false, on_vduse_vq_kick, NULL, NULL, NULL, vq); /* Make sure we don't miss any kick afer reconnecting */ eventfd_write(vduse_queue_get_fd(vq), 1); } @@ -133,9 +149,14 @@ static void vduse_blk_enable_queue(VduseDev *dev, VduseVirtq *vq) static void vduse_blk_disable_queue(VduseDev *dev, VduseVirtq *vq) { VduseBlkExport *vblk_exp = vduse_dev_get_priv(dev); + int fd = vduse_queue_get_fd(vq); - aio_set_fd_handler(vblk_exp->export.ctx, vduse_queue_get_fd(vq), - true, NULL, NULL, NULL, NULL, NULL); + if (fd < 0) { + return; + } + + aio_set_fd_handler(vblk_exp->export.ctx, fd, false, + NULL, NULL, NULL, NULL, NULL); } static const VduseOps vduse_blk_ops = { @@ -152,42 +173,19 @@ static void on_vduse_dev_kick(void *opaque) static void vduse_blk_attach_ctx(VduseBlkExport *vblk_exp, AioContext *ctx) { - int i; - aio_set_fd_handler(vblk_exp->export.ctx, vduse_dev_get_fd(vblk_exp->dev), - true, on_vduse_dev_kick, NULL, NULL, NULL, + false, on_vduse_dev_kick, NULL, NULL, NULL, vblk_exp->dev); - for (i = 0; i < vblk_exp->num_queues; i++) { - VduseVirtq *vq = vduse_dev_get_queue(vblk_exp->dev, i); - int fd = vduse_queue_get_fd(vq); - - if (fd < 0) { - continue; - } - aio_set_fd_handler(vblk_exp->export.ctx, fd, true, - on_vduse_vq_kick, NULL, NULL, NULL, vq); - } + /* Virtqueues are handled by vduse_blk_drained_end() */ } static void vduse_blk_detach_ctx(VduseBlkExport *vblk_exp) { - int i; - - for (i = 0; i < vblk_exp->num_queues; i++) { - VduseVirtq *vq = vduse_dev_get_queue(vblk_exp->dev, i); - int fd = vduse_queue_get_fd(vq); - - if (fd < 0) { - continue; - } - aio_set_fd_handler(vblk_exp->export.ctx, fd, - true, NULL, NULL, NULL, NULL, NULL); - } aio_set_fd_handler(vblk_exp->export.ctx, vduse_dev_get_fd(vblk_exp->dev), - true, NULL, NULL, NULL, NULL, NULL); + false, NULL, NULL, NULL, NULL, NULL); - AIO_WAIT_WHILE(vblk_exp->export.ctx, vblk_exp->inflight > 0); + /* Virtqueues are handled by vduse_blk_drained_begin() */ } @@ -220,8 +218,55 @@ static void vduse_blk_resize(void *opaque) (char *)&config.capacity); } +static void vduse_blk_stop_virtqueues(VduseBlkExport *vblk_exp) +{ + for (uint16_t i = 0; i < vblk_exp->num_queues; i++) { + VduseVirtq *vq = vduse_dev_get_queue(vblk_exp->dev, i); + vduse_blk_disable_queue(vblk_exp->dev, vq); + } + + vblk_exp->vqs_started = false; +} + +static void vduse_blk_start_virtqueues(VduseBlkExport *vblk_exp) +{ + vblk_exp->vqs_started = true; + + for (uint16_t i = 0; i < vblk_exp->num_queues; i++) { + VduseVirtq *vq = vduse_dev_get_queue(vblk_exp->dev, i); + vduse_blk_enable_queue(vblk_exp->dev, vq); + } +} + +static void vduse_blk_drained_begin(void *opaque) +{ + BlockExport *exp = opaque; + VduseBlkExport *vblk_exp = container_of(exp, VduseBlkExport, export); + + vduse_blk_stop_virtqueues(vblk_exp); +} + +static void vduse_blk_drained_end(void *opaque) +{ + BlockExport *exp = opaque; + VduseBlkExport *vblk_exp = container_of(exp, VduseBlkExport, export); + + vduse_blk_start_virtqueues(vblk_exp); +} + +static bool vduse_blk_drained_poll(void *opaque) +{ + BlockExport *exp = opaque; + VduseBlkExport *vblk_exp = container_of(exp, VduseBlkExport, export); + + return qatomic_read(&vblk_exp->inflight) > 0; +} + static const BlockDevOps vduse_block_ops = { - .resize_cb = vduse_blk_resize, + .resize_cb = vduse_blk_resize, + .drained_begin = vduse_blk_drained_begin, + .drained_end = vduse_blk_drained_end, + .drained_poll = vduse_blk_drained_poll, }; static int vduse_blk_exp_create(BlockExport *exp, BlockExportOptions *opts, @@ -268,6 +313,7 @@ static int vduse_blk_exp_create(BlockExport *exp, BlockExportOptions *opts, vblk_exp->handler.serial = g_strdup(vblk_opts->serial ?: ""); vblk_exp->handler.logical_block_size = logical_block_size; vblk_exp->handler.writable = opts->writable; + vblk_exp->vqs_started = true; config.capacity = cpu_to_le64(blk_getlength(exp->blk) >> VIRTIO_BLK_SECTOR_BITS); @@ -322,14 +368,20 @@ static int vduse_blk_exp_create(BlockExport *exp, BlockExportOptions *opts, vduse_dev_setup_queue(vblk_exp->dev, i, queue_size); } - aio_set_fd_handler(exp->ctx, vduse_dev_get_fd(vblk_exp->dev), true, + aio_set_fd_handler(exp->ctx, vduse_dev_get_fd(vblk_exp->dev), false, on_vduse_dev_kick, NULL, NULL, NULL, vblk_exp->dev); blk_add_aio_context_notifier(exp->blk, blk_aio_attached, blk_aio_detach, vblk_exp); - blk_set_dev_ops(exp->blk, &vduse_block_ops, exp); + /* + * We handle draining ourselves using an in-flight counter and by disabling + * virtqueue fd handlers. Do not queue BlockBackend requests, they need to + * complete so the in-flight counter reaches zero. + */ + blk_set_disable_request_queuing(exp->blk, true); + return 0; err: vduse_dev_destroy(vblk_exp->dev); @@ -344,6 +396,9 @@ static void vduse_blk_exp_delete(BlockExport *exp) VduseBlkExport *vblk_exp = container_of(exp, VduseBlkExport, export); int ret; + assert(qatomic_read(&vblk_exp->inflight) == 0); + + vduse_blk_detach_ctx(vblk_exp); blk_remove_aio_context_notifier(exp->blk, blk_aio_attached, blk_aio_detach, vblk_exp); ret = vduse_dev_destroy(vblk_exp->dev); @@ -354,13 +409,12 @@ static void vduse_blk_exp_delete(BlockExport *exp) g_free(vblk_exp->handler.serial); } +/* Called with exp->ctx acquired */ static void vduse_blk_exp_request_shutdown(BlockExport *exp) { VduseBlkExport *vblk_exp = container_of(exp, VduseBlkExport, export); - aio_context_acquire(vblk_exp->export.ctx); - vduse_blk_detach_ctx(vblk_exp); - aio_context_acquire(vblk_exp->export.ctx); + vduse_blk_stop_virtqueues(vblk_exp); } const BlockExportDriver blk_exp_vduse_blk = { -- 2.40.1