From nobody Sat Nov 15 22:36:45 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1747228722570644.095967199541; Wed, 14 May 2025 06:18:42 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uFBqs-0000fz-IO; Wed, 14 May 2025 09:08:51 -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 1uFBk0-0007uJ-Mt; Wed, 14 May 2025 09:01:46 -0400 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uFBjt-0008JC-3t; Wed, 14 May 2025 09:01:41 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id AA482121B00; Wed, 14 May 2025 15:57:50 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id 5637620B86D; Wed, 14 May 2025 15:58:00 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Christian Schoenebeck , Greg Kurz , Michael Tokarev Subject: [Stable-9.2.4 33/34] 9pfs: fix concurrent v9fs_reclaim_fd() calls Date: Wed, 14 May 2025 15:57:55 +0300 Message-Id: <20250514125758.92030-33-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1747228751270019000 Content-Type: text/plain; charset="utf-8" From: Christian Schoenebeck Even though this function is serialized to be always called from main thread, v9fs_reclaim_fd() is dispatching the coroutine to a worker thread in between via its v9fs_co_*() calls, hence leading to the situation where v9fs_reclaim_fd() is effectively executed multiple times simultaniously, which renders its LRU algorithm useless and causes high latency. Fix this by adding a simple boolean variable to ensure this function is only called once at a time. No synchronization needed for this boolean variable as this function is only entered and returned on main thread. Fixes: 7a46274529c ('hw/9pfs: Add file descriptor reclaim support') Signed-off-by: Christian Schoenebeck Reviewed-by: Greg Kurz Message-Id: <5c622067efd66dd4ee5eca740dcf263f41db20b2.1741339452.git.qemu_o= ss@crudebyte.com> (cherry picked from commit 61da38db70affd925226ce1e8a61d761c20d045b) Signed-off-by: Michael Tokarev diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 578517739a..f9aad55fdf 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -435,6 +435,12 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu) GHashTableIter iter; gpointer fid; =20 + /* prevent multiple coroutines running this function simultaniously */ + if (s->reclaiming) { + return; + } + s->reclaiming =3D true; + g_hash_table_iter_init(&iter, s->fids); =20 QSLIST_HEAD(, V9fsFidState) reclaim_list =3D @@ -510,6 +516,8 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu) */ put_fid(pdu, f); } + + s->reclaiming =3D false; } =20 /* @@ -4291,6 +4299,8 @@ int v9fs_device_realize_common(V9fsState *s, const V9= fsTransport *t, s->ctx.fst =3D &fse->fst; fsdev_throttle_init(s->ctx.fst); =20 + s->reclaiming =3D false; + rc =3D 0; out: if (rc) { diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h index 5e041e1f60..259ad32ed1 100644 --- a/hw/9pfs/9p.h +++ b/hw/9pfs/9p.h @@ -362,6 +362,7 @@ struct V9fsState { uint64_t qp_ndevices; /* Amount of entries in qpd_table. */ uint16_t qp_affix_next; uint64_t qp_fullpath_next; + bool reclaiming; }; =20 /* 9p2000.L open flags */ --=20 2.39.5