Subject: [PATCH] NFS: Use parallel read operations to do direct read requests

 The initial implementation of NFS direct reads was entirely synchronous.
 The direct read logic issued one NFS READ operation at a time, and waited
 for the server's reply before issuing the next one.  For large direct
 read requests, this is unnecessarily slow.

 This patch changes the NFS direct read path to dispatch NFS READ operations
 for a single direct read request in parallel and wait for them once.  The
 direct read path is still synchronous in nature, but because the NFS READ
 operations are going in parallel, the completion wait should be much shorter.
Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@fys.uio.no>

fs/nfs/inode.c

@@ -968,7 +968,7 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
 	/* Protect against RPC races by saving the change attribute */
 	verifier = nfs_save_change_attribute(inode);
 	status = NFS_PROTO(inode)->getattr(server, NFS_FH(inode), &fattr);
-	if (status) {
+	if (status != 0) {
 		dfprintk(PAGECACHE, "nfs_revalidate_inode: (%s/%Ld) getattr failed, error=%d\n",
 			 inode->i_sb->s_id,
 			 (long long)NFS_FILEID(inode), status);
@@ -1828,9 +1828,13 @@ static struct file_system_type nfs4_fs_type = {
 extern int nfs_init_nfspagecache(void);
 extern void nfs_destroy_nfspagecache(void);
 extern int nfs_init_readpagecache(void);
-extern int nfs_destroy_readpagecache(void);
+extern void nfs_destroy_readpagecache(void);
 extern int nfs_init_writepagecache(void);
-extern int nfs_destroy_writepagecache(void);
+extern void nfs_destroy_writepagecache(void);
+#ifdef CONFIG_NFS_DIRECTIO
+extern int nfs_init_directcache(void);
+extern void nfs_destroy_directcache(void);
+#endif
 
 static kmem_cache_t * nfs_inode_cachep;
 
@@ -1911,6 +1915,12 @@ static int __init init_nfs_fs(void)
 	if (err)
 		goto out1;
 
+#ifdef CONFIG_NFS_DIRECTIO
+	err = nfs_init_directcache();
+	if (err)
+		goto out0;
+#endif
+
 #ifdef CONFIG_PROC_FS
 	rpc_proc_register(&nfs_rpcstat);
 #endif
@@ -1921,8 +1931,14 @@ static int __init init_nfs_fs(void)
 		goto out;
 	return 0;
 out:
+#ifdef CONFIG_PROC_FS
 	rpc_proc_unregister("nfs");
+#endif
 	nfs_destroy_writepagecache();
+#ifdef CONFIG_NFS_DIRECTIO
+out0:
+	nfs_destroy_directcache();
+#endif
 out1:
 	nfs_destroy_readpagecache();
 out2:
@@ -1935,6 +1951,9 @@ static int __init init_nfs_fs(void)
 
 static void __exit exit_nfs_fs(void)
 {
+#ifdef CONFIG_NFS_DIRECTIO
+	nfs_destroy_directcache();
+#endif
 	nfs_destroy_writepagecache();
 	nfs_destroy_readpagecache();
 	nfs_destroy_inodecache();