[PATCH] Avoid excessive stack usage in NFS

Assigning '*wdata' with a dynamic initializer creates a
temporary structure copy on the stack, and then the final
data is initialized with a "memcpy()".

As a result, these NFS functions use more than 800 bytes
of stack-space.

Changing the code to just do a memset followed by explicit
initialization of the non-zero member variables takes the
stack usage down to 36 bytes. 

Here is a patch that does exactly that.

fs/nfs/read.c

@@ -103,22 +103,16 @@ nfs_readpage_sync(struct file *file, struct inode *inode, struct page *page)
 	if (!rdata)
 		return -ENOMEM;
 
-	*rdata = (struct nfs_read_data) {
-		.flags		= (IS_SWAPFILE(inode)? NFS_RPC_SWAPFLAGS : 0),
-		.cred		= NULL,
-		.inode		= inode,
-		.pages		= LIST_HEAD_INIT(rdata->pages),
-		.args		= {
-			.fh		= NFS_FH(inode),
-			.lockowner	= current->files,
-			.pages		= &page,
-			.pgbase		= 0UL,
-			.count		= rsize,
-		},
-		.res		= {
-			.fattr		= &rdata->fattr,
-		}
-	};
+	memset(rdata, 0, sizeof(*rdata));
+	rdata->flags = (IS_SWAPFILE(inode)? NFS_RPC_SWAPFLAGS : 0);
+	rdata->inode = inode;
+	INIT_LIST_HEAD(&rdata->pages);
+	rdata->args.fh = NFS_FH(inode);
+	rdata->args.lockowner = current->files;
+	rdata->args.pages = &page;
+	rdata->args.pgbase = 0UL;
+	rdata->args.count = rsize;
+	rdata->res.fattr = &rdata->fattr;
 
 	dprintk("NFS: nfs_readpage_sync(%p)\n", page);
 

fs/nfs/write.c

@@ -185,23 +185,17 @@ static int nfs_writepage_sync(struct file *file, struct inode *inode,
 	if (!wdata)
 		return -ENOMEM;
 
-	*wdata = (struct nfs_write_data) {
-		.flags		= how,
-		.cred		= NULL,
-		.inode		= inode,
-		.args		= {
-			.fh		= NFS_FH(inode),
-			.lockowner	= current->files,
-			.pages		= &page,
-			.stable		= NFS_FILE_SYNC,
-			.pgbase		= offset,
-			.count		= wsize,
-		},
-		.res		= {
-			.fattr		= &wdata->fattr,
-			.verf		= &wdata->verf,
-		},
-	};
+	memset(wdata, 0, sizeof(*wdata));
+	wdata->flags = how;
+	wdata->inode = inode;
+	wdata->args.fh = NFS_FH(inode);
+	wdata->args.lockowner = current->files;
+	wdata->args.pages = &page;
+	wdata->args.stable = NFS_FILE_SYNC;
+	wdata->args.pgbase = offset;
+	wdata->args.count = wsize;
+	wdata->res.fattr = &wdata->fattr;
+	wdata->res.verf = &wdata->verf;
 
 	dprintk("NFS:      nfs_writepage_sync(%s/%Ld %d@%Ld)\n",
 		inode->i_sb->s_id,