From owner-svn-src-all@freebsd.org Sat Oct 24 13:30:37 2020 Return-Path: Delivered-To: svn-src-all@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id CCEF3449AA8; Sat, 24 Oct 2020 13:30:37 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4CJMRd56K8z4YL4; Sat, 24 Oct 2020 13:30:37 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 934001942E; Sat, 24 Oct 2020 13:30:37 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 09ODUbjh089522; Sat, 24 Oct 2020 13:30:37 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 09ODUb6x089521; Sat, 24 Oct 2020 13:30:37 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <202010241330.09ODUb6x089521@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Sat, 24 Oct 2020 13:30:37 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r366997 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 366997 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 24 Oct 2020 13:30:37 -0000 Author: mjg Date: Sat Oct 24 13:30:37 2020 New Revision: 366997 URL: https://svnweb.freebsd.org/changeset/base/366997 Log: vfs: fix a race where reclaim vholds freed vnodes Reported by: pho Tested by: pho (previous version) Fixes: r366974 ("vfs: stop taking the interlock in vnode reclaim") Modified: head/sys/kern/vfs_subr.c Modified: head/sys/kern/vfs_subr.c ============================================================================== --- head/sys/kern/vfs_subr.c Sat Oct 24 13:16:10 2020 (r366996) +++ head/sys/kern/vfs_subr.c Sat Oct 24 13:30:37 2020 (r366997) @@ -109,6 +109,7 @@ static void syncer_shutdown(void *arg, int howto); static int vtryrecycle(struct vnode *vp); static void v_init_counters(struct vnode *); static void vgonel(struct vnode *); +static bool vhold_recycle(struct vnode *); static void vfs_knllock(void *arg); static void vfs_knlunlock(void *arg); static void vfs_knl_assert_locked(void *arg); @@ -1126,7 +1127,8 @@ restart: goto next_iter; } - vhold(vp); + if (!vhold_recycle(vp)) + goto next_iter; TAILQ_REMOVE(&vnode_list, mvp, v_vnodelist); TAILQ_INSERT_AFTER(&vnode_list, vp, mvp, v_vnodelist); mtx_unlock(&vnode_list_mtx); @@ -1231,7 +1233,8 @@ restart: if (__predict_false(vp->v_type == VBAD || vp->v_type == VNON)) { continue; } - vhold(vp); + if (!vhold_recycle(vp)) + continue; count--; mtx_unlock(&vnode_list_mtx); vtryrecycle(vp); @@ -3248,13 +3251,11 @@ vholdnz(struct vnode *vp) * However, while this is more performant, it hinders debugging by eliminating * the previously mentioned invariant. */ -bool -vhold_smr(struct vnode *vp) +static bool __always_inline +_vhold_cond(struct vnode *vp) { int count; - VFS_SMR_ASSERT_ENTERED(); - count = atomic_load_int(&vp->v_holdcnt); for (;;) { if (count & VHOLD_NO_SMR) { @@ -3270,6 +3271,28 @@ vhold_smr(struct vnode *vp) return (true); } } +} + +bool +vhold_smr(struct vnode *vp) +{ + + VFS_SMR_ASSERT_ENTERED(); + return (_vhold_cond(vp)); +} + +/* + * Special case for vnode recycling. + * + * Vnodes are present on the global list until UMA takes them out. + * Attempts to recycle only need the relevant lock and have no use for SMR. + */ +static bool +vhold_recycle(struct vnode *vp) +{ + + mtx_assert(&vnode_list_mtx, MA_OWNED); + return (_vhold_cond(vp)); } static void __noinline