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 X-Spam-Level: X-Spam-Status: No, score=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68D7CC433B4 for ; Tue, 18 May 2021 12:36:24 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id C73F46124C for ; Tue, 18 May 2021 12:36:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C73F46124C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52612 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1liyxS-0006WW-OC for qemu-devel@archiver.kernel.org; Tue, 18 May 2021 08:36:22 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47286) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1liyoM-0004Ek-UV for qemu-devel@nongnu.org; Tue, 18 May 2021 08:26:59 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:36044) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1liyoK-0004il-FF for qemu-devel@nongnu.org; Tue, 18 May 2021 08:26:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1621340814; 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=gxu4dXdf0eOqXf14fATiu/H99i4nPLwxb/xOalwebso=; b=AtBB4GroxBuUQvWKUZSB28SsyXSRxIAzHMmnO+nOBeKjKINreJOrL2UUOYCcRT7RPWB/cI l4Ez94cR/AjGbT5AkzYH7xhfpfFMoygODZ1YLjswguWiM8T5T+Ifk6NdtOx13P+EnGkoC/ QrRsduFvo/KWjHVaDlLRM2aWpuShHLs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-512-dTrK5jZSMiS72GhynqYEbw-1; Tue, 18 May 2021 08:26:53 -0400 X-MC-Unique: dTrK5jZSMiS72GhynqYEbw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 564B5107ACE3 for ; Tue, 18 May 2021 12:26:52 +0000 (UTC) Received: from work-vm (ovpn-115-45.ams2.redhat.com [10.36.115.45]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 162225D9C0; Tue, 18 May 2021 12:26:47 +0000 (UTC) Date: Tue, 18 May 2021 13:26:45 +0100 From: "Dr. David Alan Gilbert" To: Vivek Goyal Subject: Re: [PATCH 5/7] virtiofsd: Simplify skip byte logic Message-ID: References: <20210511213736.281016-1-vgoyal@redhat.com> <20210511213736.281016-6-vgoyal@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210511213736.281016-6-vgoyal@redhat.com> User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.374, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Vivek Goyal (vgoyal@redhat.com) wrote: > We need to skip bytes in two cases. > > a. Before we start reading into in_sg, we need to skip iov_len bytes > in the beginning which typically will have fuse_out_header. > > b. If preadv() does a short read, then we need to retry preadv() with > remainig bytes and skip the bytes preadv() read in short read. > > For case a, there is no reason that skipping logic be inside the while > loop. Move it outside. And only retain logic "b" inside while loop. > > Also get rid of variable "skip_size". Looks like we can do without it. > > Signed-off-by: Vivek Goyal Yep, now iov_discard_front makes it easy to skip. Reviewed-by: Dr. David Alan Gilbert > --- > tools/virtiofsd/fuse_virtio.c | 14 ++++---------- > 1 file changed, 4 insertions(+), 10 deletions(-) > > diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c > index ccad2b3f8a..434fe401cf 100644 > --- a/tools/virtiofsd/fuse_virtio.c > +++ b/tools/virtiofsd/fuse_virtio.c > @@ -392,17 +392,11 @@ int virtio_send_data_iov(struct fuse_session *se, struct fuse_chan *ch, > unsigned int in_sg_cpy_count = in_num; > > /* skip over parts of in_sg that contained the header iov */ > - size_t skip_size = iov_len; > + iov_discard_front(&in_sg_ptr, &in_sg_cpy_count, iov_len); > > do { > - if (skip_size != 0) { > - iov_discard_front(&in_sg_ptr, &in_sg_cpy_count, skip_size); > - } > - > - fuse_log(FUSE_LOG_DEBUG, > - "%s: after skip skip_size=%zd in_sg_cpy_count=%d " > - "len remaining=%zd\n", __func__, skip_size, in_sg_cpy_count, > - len); > + fuse_log(FUSE_LOG_DEBUG, "%s: in_sg_cpy_count=%d len remaining=%zd\n", > + __func__, in_sg_cpy_count, len); > > ret = preadv(buf->buf[0].fd, in_sg_ptr, in_sg_cpy_count, > buf->buf[0].pos); > @@ -421,7 +415,7 @@ int virtio_send_data_iov(struct fuse_session *se, struct fuse_chan *ch, > if (ret < len && ret) { > fuse_log(FUSE_LOG_DEBUG, "%s: ret < len\n", __func__); > /* Skip over this much next time around */ > - skip_size = ret; > + iov_discard_front(&in_sg_ptr, &in_sg_cpy_count, ret); > buf->buf[0].pos += ret; > len -= ret; > > -- > 2.25.4 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK