From nobody Wed Nov 24 11:30:25 2021 X-Original-To: dev-commits-src-main@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 566B51889008; Wed, 24 Nov 2021 11:30:40 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (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 did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4Hzf2R2L59z4W2k; Wed, 24 Nov 2021 11:30:39 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.16.1/8.16.1) with ESMTPS id 1AOBUPUa084962 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 24 Nov 2021 13:30:28 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua 1AOBUPUa084962 Received: (from kostik@localhost) by tom.home (8.16.1/8.16.1/Submit) id 1AOBUPSK084956; Wed, 24 Nov 2021 13:30:25 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 24 Nov 2021 13:30:25 +0200 From: Konstantin Belousov To: Peter Jeremy Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 8ef0c11e7ce7 - main - nfsclient: upgrade vnode lock in VOP_OPEN()/VOP_CLOSE() if we need to flush buffers Message-ID: References: <202111161714.1AGHEtBA084291@gitrepo.freebsd.org> List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-main@freebsd.org X-BeenThere: dev-commits-src-main@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.5 X-Spam-Checker-Version: SpamAssassin 3.4.5 (2021-03-20) on tom.home X-Rspamd-Queue-Id: 4Hzf2R2L59z4W2k X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: N On Wed, Nov 24, 2021 at 07:01:56PM +1100, Peter Jeremy wrote: > On 2021-Nov-24 05:12:19 +0200, Konstantin Belousov wrote: > >Try this (combined two patches). > > That's helped. I can now swapon and swapoff but not actually use swap: > KDB: stack backtrace: > db_trace_self() at db_trace_self > db_trace_self_wrapper() at db_trace_self_wrapper+0x30 > assert_vop_locked() at assert_vop_locked+0x58 > VOP_STRATEGY_APV() at VOP_STRATEGY_APV+0x54 > bufstrategy() at bufstrategy+0x4c > swap_pager_putpages() at swap_pager_putpages+0x108 > vm_pageout_flush() at vm_pageout_flush+0x108 > vm_pageout_cluster() at vm_pageout_cluster+0x464 > vm_pageout_laundry_worker() at vm_pageout_laundry_worker+0x910 > fork_exit() at fork_exit+0x74 > fork_trampoline() at fork_trampoline+0x14 > vnode 0xffffa00008840700: type VREG > usecount 1, writecount 0, refcount 2 seqc users 0 > hold count flags () > flags (VV_VMSIZEVNLOCK) > v_object 0xffffa00008df3738 ref 0 pages 0 cleanbuf 0 dirtybuf 0 > lock type nfs: UNLOCKED > fileid 30984 fsid 0x3a3a00ff01 > VOP_STRATEGY: 0xffffa00008840700 is not locked but should be > KDB: enter: lock violation Please try this, but it may require more work. In particular, watch out for deadlock: the swapped out pages are busied before swap vnode is locked. By itself it is fine, but if some other io happens to the swap vnode, it might become problematic. diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c index 9bc506c9b6b8..6daedd02649d 100644 --- a/sys/vm/swap_pager.c +++ b/sys/vm/swap_pager.c @@ -2366,8 +2366,8 @@ sys_swapon(struct thread *td, struct swapon_args *uap) goto done; } - NDINIT(&nd, LOOKUP, ISOPEN | FOLLOW | AUDITVNODE1, UIO_USERSPACE, - uap->name, td); + NDINIT(&nd, LOOKUP, ISOPEN | FOLLOW | LOCKLEAF | AUDITVNODE1, + UIO_USERSPACE, uap->name, td); error = namei(&nd); if (error) goto done; @@ -2387,8 +2387,10 @@ sys_swapon(struct thread *td, struct swapon_args *uap) error = swaponvp(td, vp, attr.va_size / DEV_BSIZE); } - if (error) - vrele(vp); + if (error != 0) + vput(vp); + else + VOP_UNLOCK(vp); done: sx_xunlock(&swdev_syscall_lock); return (error); @@ -3012,7 +3014,7 @@ swapongeom(struct vnode *vp) { int error; - vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); + ASSERT_VOP_ELOCKED(vp, "swapongeom"); if (vp->v_type != VCHR || VN_IS_DOOMED(vp)) { error = ENOENT; } else { @@ -3020,7 +3022,6 @@ swapongeom(struct vnode *vp) error = swapongeom_locked(vp->v_rdev, vp); g_topology_unlock(); } - VOP_UNLOCK(vp); return (error); } @@ -3042,24 +3043,30 @@ swapdev_strategy(struct buf *bp, struct swdevt *sp) vp2 = sp->sw_id; vhold(vp2); if (bp->b_iocmd == BIO_WRITE) { + vn_lock(vp2, LK_EXCLUSIVE | LK_RETRY); if (bp->b_bufobj) bufobj_wdrop(bp->b_bufobj); bufobj_wref(&vp2->v_bufobj); + } else { + vn_lock(vp2, LK_SHARED | LK_RETRY); } if (bp->b_bufobj != &vp2->v_bufobj) bp->b_bufobj = &vp2->v_bufobj; bp->b_vp = vp2; bp->b_iooffset = dbtob(bp->b_blkno); bstrategy(bp); - return; + VOP_UNLOCK(vp2); } static void swapdev_close(struct thread *td, struct swdevt *sp) { + struct vnode *vp; - VOP_CLOSE(sp->sw_vp, FREAD | FWRITE, td->td_ucred, td); - vrele(sp->sw_vp); + vp = sp->sw_vp; + vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); + VOP_CLOSE(vp, FREAD | FWRITE, td->td_ucred, td); + vput(vp); } static int @@ -3068,6 +3075,7 @@ swaponvp(struct thread *td, struct vnode *vp, u_long nblks) struct swdevt *sp; int error; + ASSERT_VOP_ELOCKED(vp, "swaponvp"); if (nblks == 0) return (ENXIO); mtx_lock(&sw_dev_mtx); @@ -3079,14 +3087,12 @@ swaponvp(struct thread *td, struct vnode *vp, u_long nblks) } mtx_unlock(&sw_dev_mtx); - (void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); #ifdef MAC error = mac_system_check_swapon(td->td_ucred, vp); if (error == 0) #endif error = VOP_OPEN(vp, FREAD | FWRITE, td->td_ucred, td, NULL); - (void) VOP_UNLOCK(vp); - if (error) + if (error != 0) return (error); swaponsomething(vp, vp, nblks, swapdev_strategy, swapdev_close,