linux-kernel - Re: [PATCH -V11 1/9] exportfs: Return the minimum required handle size

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Date:	Sat, 22 May 2010 20:57:50 +0530
From:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	hch@...radead.org, viro@...iv.linux.org.uk, adilger@....com,
	corbet@....net, serue@...ibm.com, neilb@...e.de,
	hooanon05@...oo.co.jp, linux-fsdevel@...r.kernel.org,
	sfrench@...ibm.com, philippe.deniel@....FR,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -V11 1/9] exportfs: Return the minimum required handle size

On Fri, 21 May 2010 18:15:16 -0400, "J. Bruce Fields" <bfields@...ldses.org> wrote:
> On Thu, May 20, 2010 at 01:05:30PM +0530, Aneesh Kumar K.V wrote:
> > The exportfs encode handle function should return the minimum required
> > handle size. This helps user to find out the handle size by passing 0
> > handle size in the first step and then redoing to the call again with
> > the returned handle size value.
> 
> The encode_fh() interface is a little confusing.  (Not your fault,
> really, mainly it's the return value (and the special use of 255) that I
> always find odd.)
> 
> But maybe it would help to have a little more documention in the
> export_encode_fh() kerneldoc comment and/or in
> Documentation/filesystems/nfs/Exporting?
> 

Kernel documentation says 

 * encode_fh:
 *    @encode_fh should store in the file handle fragment @fh (using at most
 *    @max_len bytes) information that can be used by @decode_fh to recover the
 *    file refered to by the &struct dentry @de.  If the @connectable flag is
 *    set, the encode_fh() should store sufficient information so that a good
 *    attempt can be made to find not only the file but also it's place in the
 *    filesystem.   This typically means storing a reference to de->d_parent in
 *    the filehandle fragment.  encode_fh() should return the number of bytes
 *    stored or a negative error code such as %-ENOSPC
 *

Clearly the file system encode_fh is not returning the correct return
values. Should i fix the kernel to follow the documentation or should
the kernel documentation should be fixed. I would prefer code, because
the documentation look more easy/clear to follow that returning value 255.

-aneesh
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