From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A43C5EEA9 for ; Tue, 15 Apr 2025 01:40:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744681235; cv=none; b=bNuGsJ4cvzC2dXXXmn0j5xMqGe5goDJp0cDFrZZ0RHQZy3ZpKuCWK/pQnubHYONiM6iORa/wkL94TPLzrw2NLr0sc8nWcwfFQfjZwaN6IoUFqVGbMEJtzIo3XodAk25s8uAFBEMYQ2FQGPQNHBK3izbcFd4fQ8cIWzTZJKP6Vu4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744681235; c=relaxed/simple; bh=waTqZlG5RUrdk/kyX1B3JrEAaqCI6o8Wzn0Eb0H8FxQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JFnHfsaJWzaQn6S2qjw5ioVluUg25dShZ0Tg3T0F8+aUgKCGLM02lI+BQjBkaOfoLssjvBkzVyoR7VCWhbHuDo31lL1Mx3HEFYxnJmgBNCSMPVP1yP05Eq4o/6IbfVXceIZoqygjFumypDwh1A8NfNqUFkGppu0hfCxlgtUdVQU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=JKIjm79w; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="JKIjm79w" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744681230; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=BzJIIGO4h1ov0FNztGZbtQ8RL/hoNax/EvxMwQw1rZA=; b=JKIjm79wOR2eC48dnCxbWGYxE8ykAly3vuJRhgRwHNvVOiTIYt3bW9PdF0ddeN/w3L8pYW /publv+/xIND17TGDkRQMdzGaOiUT9O6BulQfP+scKN/p5qlOGj4CEF+C3NmeRSP1/ZBBF f7VFgfd09oLLqcztfOjANO+kmtD4b/g= Received: from mx-prod-mc-05.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-261-MPbOv-2yNCiT8WkrDukkkw-1; Mon, 14 Apr 2025 21:40:23 -0400 X-MC-Unique: MPbOv-2yNCiT8WkrDukkkw-1 X-Mimecast-MFC-AGG-ID: MPbOv-2yNCiT8WkrDukkkw_1744681221 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EDCDD1956089; Tue, 15 Apr 2025 01:40:20 +0000 (UTC) Received: from fedora (unknown [10.72.116.40]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 68D041808867; Tue, 15 Apr 2025 01:40:17 +0000 (UTC) Date: Tue, 15 Apr 2025 09:40:12 +0800 From: Ming Lei To: Uday Shankar Cc: Jens Axboe , linux-block@vger.kernel.org, Caleb Sander Mateos Subject: Re: [PATCH 2/9] ublk: properly serialize all FETCH_REQs Message-ID: References: <20250414112554.3025113-1-ming.lei@redhat.com> <20250414112554.3025113-3-ming.lei@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On Mon, Apr 14, 2025 at 02:52:59PM -0600, Uday Shankar wrote: > On Mon, Apr 14, 2025 at 02:39:33PM -0600, Jens Axboe wrote: > > On 4/14/25 1:58 PM, Uday Shankar wrote: > > > +static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_device *ub, > > > + struct ublk_queue *ubq, struct ublk_io *io, > > > + const struct ublksrv_io_cmd *ub_cmd, > > > + unsigned int issue_flags) > > > +{ > > > + int ret = 0; > > > + > > > + if (issue_flags & IO_URING_F_NONBLOCK) > > > + return -EAGAIN; > > > + > > > + mutex_lock(&ub->mutex); > > > > This looks like overkill, if we can trylock the mutex that should surely > > be fine? And I would imagine succeed most of the time, hence making the > > inline/fastpath fine with F_NONBLOCK? > > Yeah, makes sense. How about this? > > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c > index cdb1543fa4a9..bf4a88cb1413 100644 > --- a/drivers/block/ublk_drv.c > +++ b/drivers/block/ublk_drv.c > @@ -1832,8 +1832,8 @@ static void ublk_nosrv_work(struct work_struct *work) > > /* device can only be started after all IOs are ready */ > static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq) > + __must_hold(&ub->mutex) > { > - mutex_lock(&ub->mutex); > ubq->nr_io_ready++; > if (ublk_queue_ready(ubq)) { > ubq->ubq_daemon = current; > @@ -1845,7 +1845,6 @@ static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq) > } > if (ub->nr_queues_ready == ub->dev_info.nr_hw_queues) > complete_all(&ub->completion); > - mutex_unlock(&ub->mutex); > } > > static void ublk_handle_need_get_data(struct ublk_device *ub, int q_id, > @@ -1929,6 +1928,55 @@ static int ublk_unregister_io_buf(struct io_uring_cmd *cmd, > return io_buffer_unregister_bvec(cmd, index, issue_flags); > } > > +static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_device *ub, > + struct ublk_queue *ubq, struct ublk_io *io, > + const struct ublksrv_io_cmd *ub_cmd, > + unsigned int issue_flags) > +{ > + int ret = 0; > + > + if (!mutex_trylock(&ub->mutex)) { > + if (issue_flags & IO_URING_F_NONBLOCK) > + return -EAGAIN; > + else > + mutex_lock(&ub->mutex); Thinking of further, looks ub->mutex has been fat enough, here we can use ub->lock(spin lock) to serialize the setup, then trylock & -EAGAIN can be avoided. It is fine to replace the mutex in ublk_mark_io_ready() with spinlock actually. Thanks, Ming