Author: rmacklem
Date: Wed Aug 17 20:55:56 2011
New Revision: 224951
URL: http://svn.freebsd.org/changeset/base/224951
Log:
MFC: r224606
Fix a LOR in the NFS client which could cause a deadlock.
This was reported to the mailing list freebsd-...@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/fs/nfsclient/nfs_clnode.c
stable/8/sys/fs/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/fs/nfsclient/nfs_clnode.c
==============================================================================
--- stable/8/sys/fs/nfsclient/nfs_clnode.c Wed Aug 17 20:43:59 2011
(r224950)
+++ stable/8/sys/fs/nfsclient/nfs_clnode.c Wed Aug 17 20:55:56 2011
(r224951)
@@ -45,6 +45,7 @@ __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>
@@ -62,6 +63,8 @@ MALLOC_DECLARE(M_NEWNFSREQ);
uma_zone_t newnfsnode_zone;
+static void nfs_freesillyrename(void *arg, __unused int pending);
+
void
ncl_nhinit(void)
{
@@ -183,6 +186,20 @@ ncl_nget(struct mount *mntp, u_int8_t *f
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_NEWNFSREQ);
+}
+
int
ncl_inactive(struct vop_inactive_args *ap)
{
@@ -217,8 +234,8 @@ ncl_inactive(struct vop_inactive_args *a
*/
ncl_removeit(sp, vp);
crfree(sp->s_cred);
- vrele(sp->s_dvp);
- FREE((caddr_t)sp, M_NEWNFSREQ);
+ 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/fs/nfsclient/nfsnode.h
==============================================================================
--- stable/8/sys/fs/nfsclient/nfsnode.h Wed Aug 17 20:43:59 2011
(r224950)
+++ stable/8/sys/fs/nfsclient/nfsnode.h Wed Aug 17 20:55:56 2011
(r224951)
@@ -35,11 +35,14 @@
#ifndef _NFSCLIENT_NFSNODE_H_
#define _NFSCLIENT_NFSNODE_H_
+#include <sys/_task.h>
+
/*
* Silly rename structure that hangs off the nfsnode until the name
* can be removed by nfs_inactive()
*/
struct sillyrename {
+ struct task s_task;
struct ucred *s_cred;
struct vnode *s_dvp;
long s_namlen;
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