From patchwork Thu Jan 21 18:15:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kurz X-Patchwork-Id: 1430007 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) 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 ozlabs.org (Postfix) with ESMTPS id 4DM9Z66GpQz9sSs for ; Fri, 22 Jan 2021 05:16:14 +1100 (AEDT) Received: from localhost ([::1]:48372 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l2eVA-0004VZ-Qz for incoming@patchwork.ozlabs.org; Thu, 21 Jan 2021 13:16:12 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:42982) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l2eUM-0004Uk-Bm for qemu-devel@nongnu.org; Thu, 21 Jan 2021 13:15:23 -0500 Received: from us-smtp-delivery-44.mimecast.com ([205.139.111.44]:45802) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l2eUI-0008HE-VL for qemu-devel@nongnu.org; Thu, 21 Jan 2021 13:15:21 -0500 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-84-d21QDsZxNLSg_rSld7_aIw-1; Thu, 21 Jan 2021 13:15:13 -0500 X-MC-Unique: d21QDsZxNLSg_rSld7_aIw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0AD34100C608; Thu, 21 Jan 2021 18:15:12 +0000 (UTC) Received: from bahia.redhat.com (ovpn-112-20.ams2.redhat.com [10.36.112.20]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0D1406EF45; Thu, 21 Jan 2021 18:15:10 +0000 (UTC) From: Greg Kurz To: qemu-devel@nongnu.org Subject: [PATCH v2] 9pfs: Improve unreclaim loop Date: Thu, 21 Jan 2021 19:15:10 +0100 Message-Id: <20210121181510.1459390-1-groug@kaod.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kaod.org Received-SPF: softfail client-ip=205.139.111.44; envelope-from=groug@kaod.org; helo=us-smtp-delivery-44.mimecast.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_SOFTFAIL=0.665 autolearn=no 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: Christian Schoenebeck , Greg Kurz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" If a fid was actually re-opened by v9fs_reopen_fid(), we re-traverse the fid list from the head in case some other request created a fid that needs to be marked unreclaimable as well (ie. the client opened a new handle on the path that is being unlinked). This is suboptimal since most if not all fids that require it have likely been taken care of already. This is mostly the result of new fids being added to the head of the list. Since the list is now a QSIMPLEQ, add new fids at the end instead to avoid the need to rewind. Take a reference on the fid to ensure it doesn't go away during v9fs_reopen_fid() and that it can be safely passed to QSIMPLEQ_NEXT() afterwards. Since the associated put_fid() can also yield, same is done with the next fid. So the logic here is to get a reference on a fid and only put it back during the next iteration after we could get a reference on the next fid. Signed-off-by: Greg Kurz Reviewed-by: Christian Schoenebeck --- v2: - fix typos in changelog - drop bogus assert() --- hw/9pfs/9p.c | 46 ++++++++++++++++++++++++++++++++-------------- 1 file changed, 32 insertions(+), 14 deletions(-) diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index b65f320e6518..3864d014b43c 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -311,7 +311,7 @@ static V9fsFidState *alloc_fid(V9fsState *s, int32_t fid) * reclaim won't close the file descriptor */ f->flags |= FID_REFERENCED; - QSIMPLEQ_INSERT_HEAD(&s->fid_list, f, next); + QSIMPLEQ_INSERT_TAIL(&s->fid_list, f, next); v9fs_readdir_init(s->proto_version, &f->fs.dir); v9fs_readdir_init(s->proto_version, &f->fs_reclaim.dir); @@ -497,32 +497,50 @@ static int coroutine_fn v9fs_mark_fids_unreclaim(V9fsPDU *pdu, V9fsPath *path) { int err; V9fsState *s = pdu->s; - V9fsFidState *fidp; + V9fsFidState *fidp, *fidp_next; -again: - QSIMPLEQ_FOREACH(fidp, &s->fid_list, next) { - if (fidp->path.size != path->size) { - continue; - } - if (!memcmp(fidp->path.data, path->data, path->size)) { + fidp = QSIMPLEQ_FIRST(&s->fid_list); + if (!fidp) { + return 0; + } + + /* + * v9fs_reopen_fid() can yield : a reference on the fid must be held + * to ensure its pointer remains valid and we can safely pass it to + * QSIMPLEQ_NEXT(). The corresponding put_fid() can also yield so + * we must keep a reference on the next fid as well. So the logic here + * is to get a reference on a fid and only put it back during the next + * iteration after we could get a reference on the next fid. Start with + * the first one. + */ + for (fidp->ref++; fidp; fidp = fidp_next) { + if (fidp->path.size == path->size && + !memcmp(fidp->path.data, path->data, path->size)) { /* Mark the fid non reclaimable. */ fidp->flags |= FID_NON_RECLAIMABLE; /* reopen the file/dir if already closed */ err = v9fs_reopen_fid(pdu, fidp); if (err < 0) { + put_fid(pdu, fidp); return err; } + } + + fidp_next = QSIMPLEQ_NEXT(fidp, next); + + if (fidp_next) { /* - * Go back to head of fid list because - * the list could have got updated when - * switched to the worker thread + * Ensure the next fid survives a potential clunk request during + * put_fid() below and v9fs_reopen_fid() in the next iteration. */ - if (err == 0) { - goto again; - } + fidp_next->ref++; } + + /* We're done with this fid */ + put_fid(pdu, fidp); } + return 0; }