NFS: Optimise inode attribute cache updates

 Allow nfs_refresh_inode() also to update attributes on the inode if the
 RPC call was sent after the last call to nfs_update_inode().
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/inode.c

@@ -785,7 +785,8 @@ nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
 		else
 			init_special_inode(inode, inode->i_mode, fattr->rdev);
 
-		nfsi->read_cache_jiffies = fattr->timestamp;
+		nfsi->read_cache_jiffies = fattr->time_start;
+		nfsi->last_updated = jiffies;
 		inode->i_atime = fattr->atime;
 		inode->i_mtime = fattr->mtime;
 		inode->i_ctime = fattr->ctime;
@@ -1120,14 +1121,15 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
 		goto out;
 	}
 
+	spin_lock(&inode->i_lock);
 	status = nfs_update_inode(inode, &fattr, verifier);
 	if (status) {
+		spin_unlock(&inode->i_lock);
 		dfprintk(PAGECACHE, "nfs_revalidate_inode: (%s/%Ld) refresh failed, error=%d\n",
 			 inode->i_sb->s_id,
 			 (long long)NFS_FILEID(inode), status);
 		goto out;
 	}
-	spin_lock(&inode->i_lock);
 	cache_validity = nfsi->cache_validity;
 	nfsi->cache_validity &= ~NFS_INO_REVAL_PAGECACHE;
 
@@ -1247,7 +1249,7 @@ void nfs_end_data_update(struct inode *inode)
 }
 
 /**
- * nfs_refresh_inode - verify consistency of the inode attribute cache
+ * nfs_check_inode_attributes - verify consistency of the inode attribute cache
  * @inode - pointer to inode
  * @fattr - updated attributes
  *
@@ -1255,13 +1257,12 @@ void nfs_end_data_update(struct inode *inode)
  * so that fattr carries weak cache consistency data, then it may
  * also update the ctime/mtime/change_attribute.
  */
-int nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
+static int nfs_check_inode_attributes(struct inode *inode, struct nfs_fattr *fattr)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 	loff_t cur_size, new_isize;
 	int data_unstable;
 
-	spin_lock(&inode->i_lock);
 
 	/* Are we in the process of updating data on the server? */
 	data_unstable = nfs_caches_unstable(inode);
@@ -1325,11 +1326,40 @@ int nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
 	if (!timespec_equal(&inode->i_atime, &fattr->atime))
 		nfsi->cache_validity |= NFS_INO_INVALID_ATIME;
 
-	nfsi->read_cache_jiffies = fattr->timestamp;
-	spin_unlock(&inode->i_lock);
+	nfsi->read_cache_jiffies = fattr->time_start;
 	return 0;
 }
 
+/**
+ * nfs_refresh_inode - try to update the inode attribute cache
+ * @inode - pointer to inode
+ * @fattr - updated attributes
+ *
+ * Check that an RPC call that returned attributes has not overlapped with
+ * other recent updates of the inode metadata, then decide whether it is
+ * safe to do a full update of the inode attributes, or whether just to
+ * call nfs_check_inode_attributes.
+ */
+int nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	int status;
+
+	if ((fattr->valid & NFS_ATTR_FATTR) == 0)
+		return 0;
+	spin_lock(&inode->i_lock);
+	nfsi->cache_validity &= ~NFS_INO_REVAL_PAGECACHE;
+	if (nfs_verify_change_attribute(inode, fattr->time_start))
+		nfsi->cache_validity &= ~(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ATIME);
+	if (time_after(fattr->time_start, nfsi->last_updated))
+		status = nfs_update_inode(inode, fattr, fattr->time_start);
+	else
+		status = nfs_check_inode_attributes(inode, fattr);
+
+	spin_unlock(&inode->i_lock);
+	return status;
+}
+
 /*
  * Many nfs protocol calls return the new file attributes after
  * an operation.  Here we update the inode to reflect the state
@@ -1365,20 +1395,17 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr, unsign
 		goto out_err;
 	}
 
-	spin_lock(&inode->i_lock);
-
 	/*
 	 * Make sure the inode's type hasn't changed.
 	 */
-	if ((inode->i_mode & S_IFMT) != (fattr->mode & S_IFMT)) {
-		spin_unlock(&inode->i_lock);
+	if ((inode->i_mode & S_IFMT) != (fattr->mode & S_IFMT))
 		goto out_changed;
-	}
 
 	/*
 	 * Update the read time so we don't revalidate too often.
 	 */
-	nfsi->read_cache_jiffies = fattr->timestamp;
+	nfsi->read_cache_jiffies = fattr->time_start;
+	nfsi->last_updated = jiffies;
 
 	/* Are we racing with known updates of the metadata on the server? */
 	data_unstable = ! (nfs_verify_change_attribute(inode, verifier) ||
@@ -1467,7 +1494,6 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr, unsign
 	if (!nfs_have_delegation(inode, FMODE_READ))
 		nfsi->cache_validity |= invalid;
 
-	spin_unlock(&inode->i_lock);
 	return 0;
  out_changed:
 	/*

fs/nfs/nfs2xdr.c

@@ -143,7 +143,6 @@ xdr_decode_fattr(u32 *p, struct nfs_fattr *fattr)
 		fattr->mode = (fattr->mode & ~S_IFMT) | S_IFIFO;
 		fattr->rdev = 0;
 	}
-	fattr->timestamp = jiffies;
 	return p;
 }
 

fs/nfs/nfs3xdr.c

@@ -174,7 +174,6 @@ xdr_decode_fattr(u32 *p, struct nfs_fattr *fattr)
 
 	/* Update the mode bits */
 	fattr->valid |= (NFS_ATTR_FATTR | NFS_ATTR_FATTR_V3);
-	fattr->timestamp = jiffies;
 	return p;
 }
 

fs/nfs/nfs4xdr.c

@@ -2799,10 +2799,8 @@ static int decode_getfattr(struct xdr_stream *xdr, struct nfs_fattr *fattr, cons
 		goto xdr_error;
 	if ((status = decode_attr_time_modify(xdr, bitmap, &fattr->mtime)) != 0)
 		goto xdr_error;
-	if ((status = verify_attr_len(xdr, savep, attrlen)) == 0) {
+	if ((status = verify_attr_len(xdr, savep, attrlen)) == 0)
 		fattr->valid = NFS_ATTR_FATTR | NFS_ATTR_FATTR_V3 | NFS_ATTR_FATTR_V4;
-		fattr->timestamp = jiffies;
-	}
 xdr_error:
 	if (status != 0)
 		printk(KERN_NOTICE "%s: xdr error %d!\n", __FUNCTION__, -status);

include/linux/nfs_fs.h

@@ -141,6 +141,7 @@ struct nfs_inode {
 	unsigned long		attrtimeo_timestamp;
 	__u64			change_attr;		/* v4 only */
 
+	unsigned long		last_updated;
 	/* "Generation counter" for the attribute cache. This is
 	 * bumped whenever we update the metadata on the
 	 * server.
@@ -319,6 +320,7 @@ extern u32 root_nfs_parse_addr(char *name); /*__init*/
 static inline void nfs_fattr_init(struct nfs_fattr *fattr)
 {
 	fattr->valid = 0;
+	fattr->time_start = jiffies;
 }
 
 /*

include/linux/nfs_xdr.h

@@ -41,7 +41,7 @@ struct nfs_fattr {
 	__u32			bitmap[2];	/* NFSv4 returned attribute bitmap */
 	__u64			change_attr;	/* NFSv4 change attribute */
 	__u64			pre_change_attr;/* pre-op NFSv4 change attribute */
-	unsigned long		timestamp;
+	unsigned long		time_start;
 };
 
 #define NFS_ATTR_WCC		0x0001		/* pre-op WCC data    */