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From: Rick Macklem <rmacklem@FreeBSD.org>
Date: Wed, 17 Aug 2011 20:44:00 +0000 (UTC)
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Subject: svn commit: r224950 - stable/8/sys/nfsclient
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Author: rmacklem
Date: Wed Aug 17 20:43:59 2011
New Revision: 224950
URL: http://svn.freebsd.org/changeset/base/224950
Log:
MFC: r224604
Fix a LOR in the NFS client which could cause a deadlock.
This was reported to the mailing list freebsd-net@freebsd.org
on July 21, 2011 under the subject "LOR with nfsclient sillyrename".
The LOR occurred when nfs_inactive() called vrele(sp->s_dvp)
while holding the vnode lock on the file in s_dvp. This patch
modifies the client so that it performs the vrele(sp->s_dvp)
as a separate task to avoid the LOR. This fix was discussed
with jhb@ and kib@, who both proposed variations of it.
Modified:
stable/8/sys/nfsclient/nfs_node.c
stable/8/sys/nfsclient/nfsnode.h
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/amd64/include/xen/ (props changed)
stable/8/sys/cddl/contrib/opensolaris/ (props changed)
stable/8/sys/contrib/dev/acpica/ (props changed)
stable/8/sys/contrib/pf/ (props changed)
Modified: stable/8/sys/nfsclient/nfs_node.c
==============================================================================
--- stable/8/sys/nfsclient/nfs_node.c Wed Aug 17 19:43:41 2011 (r224949)
+++ stable/8/sys/nfsclient/nfs_node.c Wed Aug 17 20:43:59 2011 (r224950)
@@ -47,6 +47,7 @@ __FBSDID("$FreeBSD$");
#include <sys/proc.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
+#include <sys/taskqueue.h>
#include <sys/vnode.h>
#include <vm/uma.h>
@@ -59,6 +60,8 @@ __FBSDID("$FreeBSD$");
static uma_zone_t nfsnode_zone;
+static void nfs_freesillyrename(void *arg, __unused int pending);
+
#define TRUE 1
#define FALSE 0
@@ -185,6 +188,20 @@ nfs_nget(struct mount *mntp, nfsfh_t *fh
return (0);
}
+/*
+ * Do the vrele(sp->s_dvp) as a separate task in order to avoid a
+ * deadlock because of a LOR when vrele() locks the directory vnode.
+ */
+static void
+nfs_freesillyrename(void *arg, __unused int pending)
+{
+ struct sillyrename *sp;
+
+ sp = arg;
+ vrele(sp->s_dvp);
+ free(sp, M_NFSREQ);
+}
+
int
nfs_inactive(struct vop_inactive_args *ap)
{
@@ -207,8 +224,8 @@ nfs_inactive(struct vop_inactive_args *a
*/
(sp->s_removeit)(sp);
crfree(sp->s_cred);
- vrele(sp->s_dvp);
- free((caddr_t)sp, M_NFSREQ);
+ TASK_INIT(&sp->s_task, 0, nfs_freesillyrename, sp);
+ taskqueue_enqueue(taskqueue_thread, &sp->s_task);
mtx_lock(&np->n_mtx);
}
np->n_flag &= NMODIFIED;
Modified: stable/8/sys/nfsclient/nfsnode.h
==============================================================================
--- stable/8/sys/nfsclient/nfsnode.h Wed Aug 17 19:43:41 2011 (r224949)
+++ stable/8/sys/nfsclient/nfsnode.h Wed Aug 17 20:43:59 2011 (r224950)
@@ -36,6 +36,7 @@
#ifndef _NFSCLIENT_NFSNODE_H_
#define _NFSCLIENT_NFSNODE_H_
+#include <sys/_task.h>
#if !defined(_NFSCLIENT_NFS_H_) && !defined(_KERNEL)
#include <nfs/nfs.h>
#endif
@@ -45,6 +46,7 @@
* can be removed by nfs_inactive()
*/
struct sillyrename {
+ struct task s_task;
struct ucred *s_cred;
struct vnode *s_dvp;
int (*s_removeit)(struct sillyrename *sp);