Module Name: src Committed By: hannken Date: Thu Nov 12 11:35:42 UTC 2015
Modified Files: src/sys/kern: vfs_vnode.c Log Message: Take the vnode lock before the vnode is marked VI_CHANGING and fed to vclean(). Prevents a deadlock with two null mounts on the same physical mount where one thread tries to vclean() a layer node and another thread tries to vget() a layer node pointing to the same physical node. Fixes PR kern/50375 layerfs (nullfs) locking problem leading to livelock To generate a diff of this commit: cvs rdiff -u -r1.45 -r1.46 src/sys/kern/vfs_vnode.c Please note that diffs are not public domain; they are subject to the copyright notices on the relevant files.
Modified files: Index: src/sys/kern/vfs_vnode.c diff -u src/sys/kern/vfs_vnode.c:1.45 src/sys/kern/vfs_vnode.c:1.46 --- src/sys/kern/vfs_vnode.c:1.45 Sun Jul 12 08:11:28 2015 +++ src/sys/kern/vfs_vnode.c Thu Nov 12 11:35:42 2015 @@ -1,4 +1,4 @@ -/* $NetBSD: vfs_vnode.c,v 1.45 2015/07/12 08:11:28 hannken Exp $ */ +/* $NetBSD: vfs_vnode.c,v 1.46 2015/11/12 11:35:42 hannken Exp $ */ /*- * Copyright (c) 1997-2011 The NetBSD Foundation, Inc. @@ -116,7 +116,7 @@ */ #include <sys/cdefs.h> -__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.45 2015/07/12 08:11:28 hannken Exp $"); +__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.46 2015/11/12 11:35:42 hannken Exp $"); #define _VFS_VNODE_PRIVATE @@ -325,15 +325,17 @@ try_nextlist: KASSERT((vp->v_iflag & VI_CLEAN) == 0); KASSERT(vp->v_freelisthd == listhd); - if (!mutex_tryenter(vp->v_interlock)) + if (vn_lock(vp, LK_EXCLUSIVE | LK_NOWAIT) != 0) continue; - if ((vp->v_iflag & VI_XLOCK) != 0) { - mutex_exit(vp->v_interlock); + if (!mutex_tryenter(vp->v_interlock)) { + VOP_UNLOCK(vp); continue; } + KASSERT((vp->v_iflag & VI_XLOCK) == 0); mp = vp->v_mount; if (fstrans_start_nowait(mp, FSTRANS_SHARED) != 0) { mutex_exit(vp->v_interlock); + VOP_UNLOCK(vp); continue; } break; @@ -643,6 +645,11 @@ vrelel(vnode_t *vp, int flags) * Note that VOP_INACTIVE() will drop the vnode lock. */ VOP_INACTIVE(vp, &recycle); + if (recycle) { + /* vclean() below will drop the lock. */ + if (vn_lock(vp, LK_EXCLUSIVE) != 0) + recycle = false; + } mutex_enter(vp->v_interlock); if (!recycle) { if (vtryrele(vp)) { @@ -867,6 +874,7 @@ holdrelel(vnode_t *vp) /* * Disassociate the underlying file system from a vnode. * + * Must be called with vnode locked and will return unlocked. * Must be called with the interlock held, and will return with it held. */ static void @@ -876,26 +884,18 @@ vclean(vnode_t *vp) bool recycle, active; int error; + KASSERT((vp->v_vflag & VV_LOCKSWORK) == 0 || + VOP_ISLOCKED(vp) == LK_EXCLUSIVE); KASSERT(mutex_owned(vp->v_interlock)); KASSERT((vp->v_iflag & VI_MARKER) == 0); + KASSERT((vp->v_iflag & (VI_XLOCK | VI_CLEAN)) == 0); KASSERT(vp->v_usecount != 0); - /* If already clean, nothing to do. */ - if ((vp->v_iflag & VI_CLEAN) != 0) { - return; - } - active = (vp->v_usecount > 1); - mutex_exit(vp->v_interlock); - - vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); - /* * Prevent the vnode from being recycled or brought into use * while we clean it out. */ - mutex_enter(vp->v_interlock); - KASSERT((vp->v_iflag & (VI_XLOCK | VI_CLEAN)) == 0); vp->v_iflag |= VI_XLOCK; if (vp->v_iflag & VI_EXECMAP) { atomic_add_int(&uvmexp.execpages, -vp->v_uobj.uo_npages); @@ -972,23 +972,26 @@ bool vrecycle(vnode_t *vp) { + if (vn_lock(vp, LK_EXCLUSIVE) != 0) + return false; + mutex_enter(vp->v_interlock); KASSERT((vp->v_iflag & VI_MARKER) == 0); if (vp->v_usecount != 1) { mutex_exit(vp->v_interlock); + VOP_UNLOCK(vp); return false; } if ((vp->v_iflag & VI_CHANGING) != 0) vwait(vp, VI_CHANGING); if (vp->v_usecount != 1) { mutex_exit(vp->v_interlock); + VOP_UNLOCK(vp); return false; - } else if ((vp->v_iflag & VI_CLEAN) != 0) { - mutex_exit(vp->v_interlock); - return true; } + KASSERT((vp->v_iflag & VI_CLEAN) == 0); vp->v_iflag |= VI_CHANGING; vclean(vp); vrelel(vp, VRELEL_CHANGING_SET); @@ -1036,6 +1039,11 @@ void vgone(vnode_t *vp) { + if (vn_lock(vp, LK_EXCLUSIVE) != 0) { + KASSERT((vp->v_iflag & VI_CLEAN) != 0); + vrele(vp); + } + mutex_enter(vp->v_interlock); if ((vp->v_iflag & VI_CHANGING) != 0) vwait(vp, VI_CHANGING);