9p: adjust 9p vfs write operation

Currently, the 9p net wire operation ensures that all data is sent by sending
multiple packets if the data requested is larger than the msize.  This is
better handled in the vfs code so that we can simplify wire operations to 
being concerned with only putting data onto and taking data off of the wire.
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_file.c

@@ -205,19 +205,38 @@ static ssize_t
 v9fs_file_write(struct file *filp, const char __user * data,
 		size_t count, loff_t * offset)
 {
-	int ret;
+	int n, rsize, total = 0;
 	struct p9_fid *fid;
+	struct p9_client *clnt;
 	struct inode *inode = filp->f_path.dentry->d_inode;
+	int origin = *offset;
 
 	P9_DPRINTK(P9_DEBUG_VFS, "data %p count %d offset %x\n", data,
 		(int)count, (int)*offset);
 
 	fid = filp->private_data;
-	ret = p9_client_write(fid, NULL, data, *offset, count);
-	if (ret > 0) {
-		invalidate_inode_pages2_range(inode->i_mapping, *offset,
-								*offset+ret);
-		*offset += ret;
+	clnt = fid->clnt;
+
+	rsize = fid->iounit;
+	if (!rsize || rsize > clnt->msize-P9_IOHDRSZ)
+		rsize = clnt->msize - P9_IOHDRSZ;
+
+	do {
+		if (count < rsize)
+			rsize = count;
+
+		n = p9_client_write(fid, NULL, data+total, *offset+total,
+									rsize);
+		if (n <= 0)
+			break;
+		count -= n;
+		total += n;
+	} while (count > 0);
+
+	if (total > 0) {
+		invalidate_inode_pages2_range(inode->i_mapping, origin,
+								origin+total);
+		*offset += total;
 	}
 
 	if (*offset > inode->i_size) {
@@ -225,7 +244,10 @@ v9fs_file_write(struct file *filp, const char __user * data,
 		inode->i_blocks = (inode->i_size + 512 - 1) >> 9;
 	}
 
-	return ret;
+	if (n < 0)
+		return n;
+
+	return total;
 }
 
 static const struct file_operations v9fs_cached_file_operations = {