linux-kernel - Re: [PATCH] nfs client: kill compile warning on NOMMU machine

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Date:	Thu, 05 Feb 2009 10:37:45 -0500
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Bryan Wu <cooloney@...nel.org>
Cc:	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfs client: kill compile warning on NOMMU machine

On Thu, 2009-02-05 at 08:28 -0500, Trond Myklebust wrote:
> On Thu, 2009-02-05 at 17:02 +0800, Bryan Wu wrote:
> > Hi guys,
> > 
> > Is it possible to merge this patch?
> 
> NACK. Although it would be nice to get rid of the warning, this patch
> does so at the price of even further obfuscating the fact that we're
> just returning -ENOSYS in the no MMU case, and by causing
> nfs_file_vm_ops (which is currently optimised away) to be compiled in
> for no good reason at all.
> 
> Trond

How about the following compromise: we get rid of the special casing
altogether and just always call generic_file_mmap. If the noMMU folks
want further optimisations, then they can inline generic_file_mmap(), so
that the compiler always takes the 'generic_file_mmap() failed' path.

Cheers
  Trond
------------------------------------------------------------
From: Trond Myklebust <Trond.Myklebust@...app.com>
Date: Thu, 5 Feb 2009 10:23:36 -0500
NFS: Kill the "defined but not used" compile error on nommu machines

Bryan Wu reports that when compiling NFS on nommu machines he gets a
"defined but not used" error on nfs_file_mmap().

The easiest fix is simply to get rid of the special casing in NFS, and
just always call generic_file_mmap() to set up the file.

Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
---

 fs/nfs/file.c |   12 +++++-------
 1 files changed, 5 insertions(+), 7 deletions(-)


diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 404c19c..1eab9c9 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -64,11 +64,7 @@ const struct file_operations nfs_file_operations = {
 	.write		= do_sync_write,
 	.aio_read	= nfs_file_read,
 	.aio_write	= nfs_file_write,
-#ifdef CONFIG_MMU
 	.mmap		= nfs_file_mmap,
-#else
-	.mmap		= generic_file_mmap,
-#endif
 	.open		= nfs_file_open,
 	.flush		= nfs_file_flush,
 	.release	= nfs_file_release,
@@ -304,11 +300,13 @@ nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
 	dprintk("NFS: mmap(%s/%s)\n",
 		dentry->d_parent->d_name.name, dentry->d_name.name);
 
-	status = nfs_revalidate_mapping(inode, file->f_mapping);
+	/* Note: generic_file_mmap() returns ENOSYS on nommu systems
+	 *       so we call that before revalidating the mapping
+	 */
+	status = generic_file_mmap(file, vma);
 	if (!status) {
 		vma->vm_ops = &nfs_file_vm_ops;
-		vma->vm_flags |= VM_CAN_NONLINEAR;
-		file_accessed(file);
+		status = nfs_revalidate_mapping(inode, file->f_mapping);
 	}
 	return status;
 }

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com
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