2 fixes that improve on the consistency of the NFS client cache.

- Change the cached mtime to a 'struct timespec' from a
  time_t. Improving the precision of the cached mtime tightens up
  NFS' "close-to-open" consistency considerably.
- Always force an over-the-wire consistency check from nfs_open()
  (unless the file is marked modified). This further improves
  NFS' "close-to-open" consistency.

Submitted by:	Mohan Srinivasan mohans at yahoo-inc dot com

4 files changed, 24 insertions, 17 deletions

diff --git a/sys/nfsclient/nfs_bio.c b/sys/nfsclient/nfs_bio.c
index 9fd12a1..bc2cf53 100644
--- a/sys/nfsclient/nfs_bio.c
+++ b/sys/nfsclient/nfs_bio.c
@@ -396,19 +396,19 @@ nfs_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
 		error = VOP_GETATTR(vp, &vattr, cred, td);
 		if (error)
 			return (error);
-		np->n_mtime = vattr.va_mtime.tv_sec;
+		np->n_mtime = vattr.va_mtime;
 	} else {
 		error = VOP_GETATTR(vp, &vattr, cred, td);
 		if (error)
 			return (error);
 		if ((np->n_flag & NSIZECHANGED)
-		    || (np->n_mtime != vattr.va_mtime.tv_sec)) {
+		    || (NFS_TIMESPEC_COMPARE(&np->n_mtime, &vattr.va_mtime))) {
 			if (vp->v_type == VDIR)
 				(nmp->nm_rpcops->nr_invaldir)(vp);
 			error = nfs_vinvalbuf(vp, V_SAVE, cred, td, 1);
 			if (error)
 				return (error);
-			np->n_mtime = vattr.va_mtime.tv_sec;
+			np->n_mtime = vattr.va_mtime;
 			np->n_flag &= ~NSIZECHANGED;
 		}
 	}
@@ -1318,7 +1318,7 @@ nfs_doio(struct vnode *vp, struct buf *bp, struct ucred *cr, struct thread *td)
 		}
 		/* ASSERT_VOP_LOCKED(vp, "nfs_doio"); */
 		if (p && (vp->v_vflag & VV_TEXT) &&
-			(np->n_mtime != np->n_vattr.va_mtime.tv_sec)) {
+		    (NFS_TIMESPEC_COMPARE(&np->n_mtime, &np->n_vattr.va_mtime))) {
 			PROC_LOCK(p);
 			killproc(p, "text file modification");
 			PROC_UNLOCK(p);
diff --git a/sys/nfsclient/nfs_subs.c b/sys/nfsclient/nfs_subs.c
index b91adae..8668a99 100644
--- a/sys/nfsclient/nfs_subs.c
+++ b/sys/nfsclient/nfs_subs.c
@@ -534,7 +534,7 @@ nfs_loadattrcache(struct vnode **vpp, struct mbuf **mdp, caddr_t *dposp,
 		vp->v_type = vtyp;
 		if (vp->v_type == VFIFO)
 			vp->v_op = &nfs_fifoops;
-		np->n_mtime = mtime.tv_sec;
+		np->n_mtime = mtime;
 	}
 	vap = &np->n_vattr;
 	vap->va_type = vtyp;
@@ -639,7 +639,7 @@ nfs_getattrcache(struct vnode *vp, struct vattr *vaper)
 	vap = &np->n_vattr;
 	nmp = VFSTONFS(vp->v_mount);
 	/* XXX n_mtime doesn't seem to be updated on a miss-and-reload */
-	timeo = (time_second - np->n_mtime) / 10;
+	timeo = (time_second - np->n_mtime.tv_sec) / 10;
 
 #ifdef NFS_ACDEBUG
 	if (nfs_acdebug>1)
@@ -941,8 +941,8 @@ nfsm_wcc_data_xx(struct vnode **v, int *f, struct mbuf **md, caddr_t *dpos)
 		if (tl == NULL)
 			return EBADRPC;
 		if (*f)
-			ttretf = (VTONFS(*v)->n_mtime ==
-			    fxdr_unsigned(u_int32_t, *(tl + 2)));
+ 			ttretf = (VTONFS(*v)->n_mtime.tv_sec == fxdr_unsigned(u_int32_t, *(tl + 2)) && 
+				  VTONFS(*v)->n_mtime.tv_nsec == fxdr_unsigned(u_int32_t, *(tl + 3))); 
 	}
 	t1 = nfsm_postop_attr_xx(v, &ttattrf, md, dpos);
 	if (t1)
diff --git a/sys/nfsclient/nfs_vnops.c b/sys/nfsclient/nfs_vnops.c
index b9fd2a6..a4dbe18 100644
--- a/sys/nfsclient/nfs_vnops.c
+++ b/sys/nfsclient/nfs_vnops.c
@@ -417,22 +417,22 @@ nfs_open(struct vop_open_args *ap)
 		error = VOP_GETATTR(vp, &vattr, ap->a_cred, ap->a_td);
 		if (error)
 			return (error);
-		np->n_mtime = vattr.va_mtime.tv_sec;
+		np->n_mtime = vattr.va_mtime;
 	} else {
+		np->n_attrstamp = 0;
 		error = VOP_GETATTR(vp, &vattr, ap->a_cred, ap->a_td);
 		if (error)
 			return (error);
-		if (np->n_mtime != vattr.va_mtime.tv_sec) {
+		if (NFS_TIMESPEC_COMPARE(&np->n_mtime, &vattr.va_mtime)) {
 			if (vp->v_type == VDIR)
 				np->n_direofoffset = 0;
 			error = nfs_vinvalbuf(vp, V_SAVE,
 				ap->a_cred, ap->a_td, 1);
 			if (error == EINTR || error == EIO)
 				return (error);
-			np->n_mtime = vattr.va_mtime.tv_sec;
+			np->n_mtime = vattr.va_mtime;
 		}
 	}
-	np->n_attrstamp = 0; /* For Open/Close consistency */
 	return (0);
 }
 
@@ -484,7 +484,6 @@ nfs_close(struct vop_close_args *ap)
 		vm_object_page_clean(vp->v_object, 0, 0, 0);
 		VM_OBJECT_UNLOCK(vp->v_object);
 	    }
-
 	    if (np->n_flag & NMODIFIED) {
 		if (NFS_ISV3(vp)) {
 		    /*
@@ -506,8 +505,14 @@ nfs_close(struct vop_close_args *ap)
 		} else {
 		    error = nfs_vinvalbuf(vp, V_SAVE, ap->a_cred, ap->a_td, 1);
 		}
-		np->n_attrstamp = 0;
 	    }
+ 	    /* 
+ 	     * Invalidate the attribute cache in all cases.
+ 	     * An open is going to fetch fresh attrs any way, other procs
+ 	     * on this node that have file open will be forced to do an 
+ 	     * otw attr fetch, but this is safe.
+ 	     */
+	    np->n_attrstamp = 0;
 	    if (np->n_flag & NWRITEERR) {
 		np->n_flag &= ~NWRITEERR;
 		error = np->n_error;
@@ -1153,7 +1158,7 @@ nfs_writerpc(struct vnode *vp, struct uio *uiop, struct ucred *cred,
 		} else
 		    nfsm_loadattr(vp, NULL);
 		if (wccflag)
-		    VTONFS(vp)->n_mtime = VTONFS(vp)->n_vattr.va_mtime.tv_sec;
+		    VTONFS(vp)->n_mtime = VTONFS(vp)->n_vattr.va_mtime;
 		m_freem(mrep);
 		if (error)
 			break;
@@ -1912,7 +1917,7 @@ nfs_readdir(struct vop_readdir_args *ap)
 	if (np->n_direofoffset > 0 && uio->uio_offset >= np->n_direofoffset &&
 	    (np->n_flag & NMODIFIED) == 0) {
 		if (VOP_GETATTR(vp, &vattr, ap->a_cred, uio->uio_td) == 0 &&
-			np->n_mtime == vattr.va_mtime.tv_sec) {
+		    !NFS_TIMESPEC_COMPARE(&np->n_mtime, &vattr.va_mtime)) {
 			nfsstats.direofcache_hits++;
 			return (0);
 		}
diff --git a/sys/nfsclient/nfsnode.h b/sys/nfsclient/nfsnode.h
index 21bb0d1..4a4d835 100644
--- a/sys/nfsclient/nfsnode.h
+++ b/sys/nfsclient/nfsnode.h
@@ -97,7 +97,7 @@ struct nfsnode {
 	u_int32_t		n_mode;		/* ACCESS mode cache */
 	uid_t			n_modeuid;	/* credentials having mode */
 	time_t			n_modestamp;	/* mode cache timestamp */
-	time_t			n_mtime;	/* Prev modify time. */
+	struct timespec		n_mtime;	/* Prev modify time. */
 	time_t			n_ctime;	/* Prev create time. */
 	time_t			n_expiry;	/* Lease expiry time */
 	nfsfh_t			*n_fhp;		/* NFS File Handle */
@@ -155,6 +155,8 @@ struct nfsnode {
 #define VTONFS(vp)	((struct nfsnode *)(vp)->v_data)
 #define NFSTOV(np)	((struct vnode *)(np)->n_vnode)
 
+#define NFS_TIMESPEC_COMPARE(T1, T2)	(((T1)->tv_sec != (T2)->tv_sec) || ((T1)->tv_nsec != (T2)->tv_nsec))
+
 /*
  * Queue head for nfsiod's
  */