Date: Wed, 17 Aug 2011 20:44:00 +0000 (UTC) From: Rick Macklem <rmacklem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org Subject: svn commit: r224950 - stable/8/sys/nfsclient Message-ID: <201108172044.p7HKi0Nh022294@svn.freebsd.org>
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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);
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