[PATCH] NFS lookup code rewrite w/o open(".") fix...

  This is a resend of the NFS lookup code rewrite, but with the open(".")
VFS fix removed. (I'll resend the 'uses d_revalidate()' version
separately after a suitable delay to allow for comments.)

  Issues fixed by this patch:

 - Use the directory mtime in order to give us a hint when we should
   check for namespace changes.

 - Add support for the 'nocto' flag, in order to turn off the strict
   attribute cache revalidation on file open().

 - Simplify inode lookup. Don't check the 'fsid' field (which appears
   to be buggy in too many servers in order to be reliable). Instead
   we only rely on the inode number (a.k.a. 'fileid') and the
   (supposedly unique) filehandle.

fs/nfs/dir.c

@@ -401,6 +401,21 @@ static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 	return 0;
 }
 
+/*
+ * A check for whether or not the parent directory has changed.
+ * In the case it has, we assume that the dentries are untrustworthy
+ * and may need to be looked up again.
+ */
+static inline
+int nfs_check_verifier(struct inode *dir, struct dentry *dentry)
+{
+	if (IS_ROOT(dentry))
+		return 1;
+	if (nfs_revalidate_inode(NFS_SERVER(dir), dir))
+		return 0;
+	return time_after(dentry->d_time, NFS_MTIME_UPDATE(dir));
+}
+
 /*
  * Whenever an NFS operation succeeds, we know that the dentry
  * is valid, so we update the revalidation timestamp.
@@ -410,48 +425,31 @@ static inline void nfs_renew_times(struct dentry * dentry)
 	dentry->d_time = jiffies;
 }
 
-static inline int nfs_dentry_force_reval(struct dentry *dentry, int flags)
+static inline
+int nfs_lookup_verify_inode(struct inode *inode, int flags)
 {
-	struct inode *inode = dentry->d_inode;
-	unsigned long timeout = NFS_ATTRTIMEO(inode);
-
+	struct nfs_server *server = NFS_SERVER(inode);
 	/*
-	 * If it's the last lookup in a series, we use a stricter
-	 * cache consistency check by looking at the parent mtime.
-	 *
-	 * If it's been modified in the last hour, be really strict.
-	 * (This still means that we can avoid doing unnecessary
-	 * work on directories like /usr/share/bin etc which basically
-	 * never change).
+	 * If we're interested in close-to-open cache consistency,
+	 * then we revalidate the inode upon lookup.
 	 */
-	if (!(flags & LOOKUP_CONTINUE)) {
-		long diff = CURRENT_TIME - dentry->d_parent->d_inode->i_mtime;
-
-		if (diff < 15*60)
-			timeout = 0;
-	}
-	
-	return time_after(jiffies,dentry->d_time + timeout);
+	if (!(server->flags & NFS_MOUNT_NOCTO) && !(flags & LOOKUP_CONTINUE))
+		NFS_CACHEINV(inode);
+	return nfs_revalidate_inode(server, inode);
 }
 
 /*
  * We judge how long we want to trust negative
  * dentries by looking at the parent inode mtime.
  *
- * If mtime is close to present time, we revalidate
- * more often.
+ * If parent mtime has changed, we revalidate, else we wait for a
+ * period corresponding to the parent's attribute cache timeout value.
  */
-#define NFS_REVALIDATE_NEGATIVE (1 * HZ)
-static inline int nfs_neg_need_reval(struct dentry *dentry)
+static inline int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry)
 {
-	struct inode *dir = dentry->d_parent->d_inode;
-	unsigned long timeout = NFS_ATTRTIMEO(dir);
-	long diff = CURRENT_TIME - dir->i_mtime;
-
-	if (diff < 5*60 && timeout > NFS_REVALIDATE_NEGATIVE)
-		timeout = NFS_REVALIDATE_NEGATIVE;
-
-	return time_after(jiffies, dentry->d_time + timeout);
+	if (!nfs_check_verifier(dir, dentry))
+		return 1;
+	return time_after(jiffies, dentry->d_time + NFS_ATTRTIMEO(dir));
 }
 
 /*
@@ -462,9 +460,8 @@ static inline int nfs_neg_need_reval(struct dentry *dentry)
  * NOTE! The hit can be a negative hit too, don't assume
  * we have an inode!
  *
- * If the dentry is older than the revalidation interval, 
- * we do a new lookup and verify that the dentry is still
- * correct.
+ * If the parent directory is seen to have changed, we throw out the
+ * cached dentry and do a new lookup.
  */
 static int nfs_lookup_revalidate(struct dentry * dentry, int flags)
 {
@@ -477,13 +474,9 @@ static int nfs_lookup_revalidate(struct dentry * dentry, int flags)
 	lock_kernel();
 	dir = dentry->d_parent->d_inode;
 	inode = dentry->d_inode;
-	/*
-	 * If we don't have an inode, let's look at the parent
-	 * directory mtime to get a hint about how often we
-	 * should validate things..
-	 */
+
 	if (!inode) {
-		if (nfs_neg_need_reval(dentry))
+		if (nfs_neg_need_reval(dir, dentry))
 			goto out_bad;
 		goto out_valid;
 	}
@@ -494,48 +487,39 @@ static int nfs_lookup_revalidate(struct dentry * dentry, int flags)
 		goto out_bad;
 	}
 
-	if (!nfs_dentry_force_reval(dentry, flags))
+	/* Force a full look up iff the parent directory has changed */
+	if (nfs_check_verifier(dir, dentry)) {
+		if (nfs_lookup_verify_inode(inode, flags))
+			goto out_bad;
 		goto out_valid;
-
-	if (IS_ROOT(dentry)) {
-		__nfs_revalidate_inode(NFS_SERVER(inode), inode);
-		goto out_valid_renew;
 	}
 
-	/*
-	 * Do a new lookup and check the dentry attributes.
-	 */
+	if (NFS_STALE(inode))
+		goto out_bad;
+
 	error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
 	if (error)
 		goto out_bad;
-
-	/* Inode number matches? */
-	if (!(fattr.valid & NFS_ATTR_FATTR) ||
-	    NFS_FSID(inode) != fattr.fsid ||
-	    NFS_FILEID(inode) != fattr.fileid)
+	if (memcmp(NFS_FH(inode), &fhandle, sizeof(struct nfs_fh))!= 0)
 		goto out_bad;
-
-	/* Ok, remember that we successfully checked it.. */
-	nfs_refresh_inode(inode, &fattr);
-
-	if (nfs_inode_is_stale(inode, &fhandle, &fattr))
+	if ((error = nfs_refresh_inode(inode, &fattr)) != 0)
 		goto out_bad;
 
- out_valid_renew:
 	nfs_renew_times(dentry);
-out_valid:
+ out_valid:
 	unlock_kernel();
 	return 1;
-out_bad:
-	shrink_dcache_parent(dentry);
-	/* If we have submounts, don't unhash ! */
-	if (have_submounts(dentry))
-		goto out_valid;
-	d_drop(dentry);
-	/* Purge readdir caches. */
-	nfs_zap_caches(dir);
-	if (inode && S_ISDIR(inode->i_mode))
+ out_bad:
+	NFS_CACHEINV(dir);
+	if (inode && S_ISDIR(inode->i_mode)) {
+		/* Purge readdir caches. */
 		nfs_zap_caches(inode);
+		/* If we have submounts, don't unhash ! */
+		if (have_submounts(dentry))
+			goto out_valid;
+		shrink_dcache_parent(dentry);
+	}
+	d_drop(dentry);
 	unlock_kernel();
 	return 0;
 }
@@ -565,6 +549,7 @@ static void nfs_dentry_iput(struct dentry *dentry, struct inode *inode)
 {
 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
 		lock_kernel();
+		inode->i_nlink--;
 		nfs_complete_unlink(dentry);
 		unlock_kernel();
 	}
@@ -604,9 +589,9 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry)
 		if (inode) {
 	    no_entry:
 			d_add(dentry, inode);
-			nfs_renew_times(dentry);
 			error = 0;
 		}
+		nfs_renew_times(dentry);
 	}
 out:
 	return ERR_PTR(error);

fs/nfs/inode.c

@@ -630,39 +630,18 @@ nfs_find_actor(struct inode *inode, unsigned long ino, void *opaque)
 	struct nfs_fh		*fh = desc->fh;
 	struct nfs_fattr	*fattr = desc->fattr;
 
-	if (NFS_FSID(inode) != fattr->fsid)
-		return 0;
 	if (NFS_FILEID(inode) != fattr->fileid)
 		return 0;
 	if (memcmp(NFS_FH(inode), fh, sizeof(struct nfs_fh)) != 0)
 		return 0;
+	if (is_bad_inode(inode))
+		return 0;
 	/* Force an attribute cache update if inode->i_count == 0 */
 	if (!atomic_read(&inode->i_count))
 		NFS_CACHEINV(inode);
 	return 1;
 }
 
-int
-nfs_inode_is_stale(struct inode *inode, struct nfs_fh *fh, struct nfs_fattr *fattr)
-{
-	/* Empty inodes are not stale */
-	if (!inode->i_mode)
-		return 0;
-
-	if ((fattr->mode & S_IFMT) != (inode->i_mode & S_IFMT))
-		return 1;
-
-	if (is_bad_inode(inode) || NFS_STALE(inode))
-		return 1;
-
-	/* Has the filehandle changed? If so is the old one stale? */
-	if (memcmp(NFS_FH(inode), fh, sizeof(struct nfs_fh)) != 0 &&
-	    __nfs_revalidate_inode(NFS_SERVER(inode),inode) == -ESTALE)
-		return 1;
-
-	return 0;
-}
-
 /*
  * This is our own version of iget that looks up inodes by file handle
  * instead of inode number.  We use this technique instead of using
@@ -713,7 +692,6 @@ __nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
 		/* We can't support UPDATE_ATIME(), since the server will reset it */
 		NFS_FLAGS(inode) &= ~NFS_INO_NEW;
 		NFS_FILEID(inode) = fattr->fileid;
-		NFS_FSID(inode) = fattr->fsid;
 		memcpy(NFS_FH(inode), fh, sizeof(struct nfs_fh));
 		inode->i_flags |= S_NOATIME;
 		inode->i_mode = fattr->mode;
@@ -787,7 +765,7 @@ nfs_notify_change(struct dentry *dentry, struct iattr *attr)
 	/*
 	 * Make sure the inode is up-to-date.
 	 */
-	error = nfs_revalidate(dentry);
+	error = nfs_revalidate_inode(NFS_SERVER(inode),inode);
 	if (error) {
 #ifdef NFS_PARANOIA
 printk("nfs_notify_change: revalidate failed, error=%d\n", error);
@@ -1025,12 +1003,11 @@ __nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
 			inode->i_sb->s_id, inode->i_ino,
 			atomic_read(&inode->i_count), fattr->valid);
 
-	if (NFS_FSID(inode) != fattr->fsid ||
-	    NFS_FILEID(inode) != fattr->fileid) {
+	if (NFS_FILEID(inode) != fattr->fileid) {
 		printk(KERN_ERR "nfs_refresh_inode: inode number mismatch\n"
-		       "expected (0x%Lx/0x%Lx), got (0x%Lx/0x%Lx)\n",
-		       (long long)NFS_FSID(inode), (long long)NFS_FILEID(inode),
-		       (long long)fattr->fsid, (long long)fattr->fileid);
+		       "expected (%s/0x%Lx), got (%s/0x%Lx)\n",
+		       inode->i_sb->s_id, (long long)NFS_FILEID(inode),
+		       inode->i_sb->s_id, (long long)fattr->fileid);
 		goto out_err;
 	}
 
@@ -1100,8 +1077,11 @@ __nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
 
 	inode->i_atime = new_atime;
 
-	NFS_CACHE_MTIME(inode) = new_mtime;
-	inode->i_mtime = nfs_time_to_secs(new_mtime);
+	if (NFS_CACHE_MTIME(inode) != new_mtime) {
+		NFS_MTIME_UPDATE(inode) = jiffies;
+		NFS_CACHE_MTIME(inode) = new_mtime;
+		inode->i_mtime = nfs_time_to_secs(new_mtime);
+	}
 
 	NFS_CACHE_ISIZE(inode) = new_size;
 	inode->i_size = new_isize;
@@ -1175,10 +1155,6 @@ static struct inode *nfs_alloc_inode(struct super_block *sb)
 	if (!nfsi)
 		return NULL;
 	nfsi->flags = NFS_INO_NEW;
-	/* do we need the next 4 lines? */
-	nfsi->hash_next = NULL;
-	nfsi->hash_prev = NULL;
-	nfsi->nextscan = 0;
 	nfsi->mm_cred = NULL;
 	return &nfsi->vfs_inode;
 }

fs/nfs/nfs3proc.c

@@ -80,7 +80,8 @@ nfs3_proc_lookup(struct inode *dir, struct qstr *name,
 		status = rpc_call(NFS_CLIENT(dir), NFS3PROC_GETATTR,
 			 fhandle, fattr, 0);
 	dprintk("NFS reply lookup: %d\n", status);
-	nfs_refresh_inode(dir, &dir_attr);
+	if (status >= 0)
+		status = nfs_refresh_inode(dir, &dir_attr);
 	return status;
 }
 

include/linux/nfs_fs.h

@@ -92,7 +92,6 @@ struct nfs_inode {
 	/*
 	 * The 64bit 'inode number'
 	 */
-	__u64 fsid;
 	__u64 fileid;
 
 	/*
@@ -129,6 +128,12 @@ struct nfs_inode {
 	unsigned long		attrtimeo;
 	unsigned long		attrtimeo_timestamp;
 
+	/*
+	 * Timestamp that dates the change made to read_cache_mtime.
+	 * This is of use for dentry revalidation
+	 */
+	unsigned long		cache_mtime_jiffies;
+
 	/*
 	 * This is the cookie verifier used for NFSv3 readdir
 	 * operations
@@ -148,11 +153,6 @@ struct nfs_inode {
 				ncommit,
 				npages;
 
-	/* Flush daemon info */
-	struct inode		*hash_next,
-				*hash_prev;
-	unsigned long		nextscan;
-
 	/* Credentials for shared mmap */
 	struct rpc_cred		*mm_cred;
 
@@ -183,6 +183,7 @@ static inline struct nfs_inode *NFS_I(struct inode *inode)
 #define NFS_CONGESTED(inode)		(RPC_CONGESTED(NFS_CLIENT(inode)))
 #define NFS_COOKIEVERF(inode)		(NFS_I(inode)->cookieverf)
 #define NFS_READTIME(inode)		(NFS_I(inode)->read_cache_jiffies)
+#define NFS_MTIME_UPDATE(inode)		(NFS_I(inode)->cache_mtime_jiffies)
 #define NFS_CACHE_CTIME(inode)		(NFS_I(inode)->read_cache_ctime)
 #define NFS_CACHE_MTIME(inode)		(NFS_I(inode)->read_cache_mtime)
 #define NFS_CACHE_ISIZE(inode)		(NFS_I(inode)->read_cache_isize)
@@ -206,7 +207,6 @@ do { \
 #define NFS_NEW(inode)			(NFS_FLAGS(inode) & NFS_INO_NEW)
 
 #define NFS_FILEID(inode)		(NFS_I(inode)->fileid)
-#define NFS_FSID(inode)			(NFS_I(inode)->fsid)
 
 /* Inode Flags */
 #define NFS_USE_READDIRPLUS(inode)	((NFS_FLAGS(inode) & NFS_INO_ADVISE_RDPLUS) ? 1 : 0)