NFS: In 2.4, NFS O_DIRECT used the VFS's O_DIRECT logic to provide

   direct I/O support for NFS files.  The 2.4 VFS O_DIRECT logic was
   block based, thus the NFS client had to provide a minimum
   allowable blocksize for O_DIRECT reads and writes on NFS files. 
   For various reasons we chose 512 bytes. In 2.6, there is no
   requirement for a minimum blocksize.  NFS O_DIRECT reads and
   writes can go to any byte at any offset in a file.  Thus we revert
   the blocksize setting for NFS file systems to the previous
   behavior, which was to advertise the "wsize" setting as the
   optimal I/O block size.  This improves the performance of
   applications like 'cp' which use this value as their transfer
   size.

This patch also exposes the server's reported disk block size in the
   f_frsize of the vfsstat structure.
Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@fys.uio.no>

fs/nfs/inode.c

@@ -270,14 +270,6 @@ nfs_sb_init(struct super_block *sb, rpc_authflavor_t authflavor)
 		server->rsize = nfs_block_size(fsinfo.rtpref, NULL);
 	if (server->wsize == 0)
 		server->wsize = nfs_block_size(fsinfo.wtpref, NULL);
-	if (sb->s_blocksize == 0) {
-		if (fsinfo.wtmult == 0) {
-			sb->s_blocksize = 512;
-			sb->s_blocksize_bits = 9;
-		} else
-			sb->s_blocksize = nfs_block_bits(fsinfo.wtmult,
-							 &sb->s_blocksize_bits);
-	}
 
 	if (fsinfo.rtmax >= 512 && server->rsize > fsinfo.rtmax)
 		server->rsize = nfs_block_size(fsinfo.rtmax, NULL);
@@ -296,6 +288,11 @@ nfs_sb_init(struct super_block *sb, rpc_authflavor_t authflavor)
                 server->wsize = server->wpages << PAGE_CACHE_SHIFT;
 	}
 
+	if (sb->s_blocksize == 0)
+		sb->s_blocksize = nfs_block_bits(server->wsize,
+							 &sb->s_blocksize_bits);
+	server->wtmult = nfs_block_bits(fsinfo.wtmult, NULL);
+
 	server->dtsize = nfs_block_size(fsinfo.dtpref, NULL);
 	if (server->dtsize > PAGE_CACHE_SIZE)
 		server->dtsize = PAGE_CACHE_SIZE;
@@ -482,6 +479,7 @@ nfs_statfs(struct super_block *sb, struct kstatfs *buf)
 	if (error < 0)
 		goto out_err;
 
+	buf->f_frsize = server->wtmult;
 	buf->f_bsize = sb->s_blocksize;
 	blockbits = sb->s_blocksize_bits;
 	blockres = (1 << blockbits) - 1;

include/linux/nfs_fs_sb.h

@@ -18,6 +18,7 @@ struct nfs_server {
 	unsigned int		rpages;		/* read size (in pages) */
 	unsigned int		wsize;		/* write size */
 	unsigned int		wpages;		/* write size (in pages) */
+	unsigned int		wtmult;		/* server disk block size */
 	unsigned int		dtsize;		/* readdir size */
 	unsigned int		bsize;		/* server block size */
 	unsigned int		acregmin;	/* attr cache timeouts */