linux-kernel - Re: [PATCH -V20 01/12] exportfs: Return the minimum required handle size

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Date:	Wed, 29 Sep 2010 11:04:52 +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, neilb@...e.de, npiggin@...nel.dk,
	hooanon05@...oo.co.jp, miklos@...redi.hu,
	linux-fsdevel@...r.kernel.org, sfrench@...ibm.com,
	philippe.deniel@....FR, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -V20 01/12] exportfs: Return the minimum required handle size

On Tue, 28 Sep 2010 15:52:50 -0400, "J. Bruce Fields" <bfields@...ldses.org> wrote:
> On Wed, Sep 29, 2010 at 01:06:39AM +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.
> 
> Just nits; seems OK otherwise:
> 
> > diff --git a/fs/ocfs2/export.c b/fs/ocfs2/export.c
> > index 19ad145..250a347 100644
> > --- a/fs/ocfs2/export.c
> > +++ b/fs/ocfs2/export.c
> > @@ -201,8 +201,14 @@ static int ocfs2_encode_fh(struct dentry *dentry, u32 *fh_in, int *max_len,
> >  		   dentry->d_name.len, dentry->d_name.name,
> >  		   fh, len, connectable);
> >  
> > -	if (len < 3 || (connectable && len < 6)) {
> > +	if (connectable && (len < 6)) {
> >  		mlog(ML_ERROR, "fh buffer is too small for encoding\n");
> 
> Should that really be a printk(KERN_ERR, ...) if this is an expected use
> of the interface?
> 
> > +		*max_len = 6;
> > +		type = 255;
> > +		goto bail;
> > +	} else if (len < 3) {
> > +		mlog(ML_ERROR, "fh buffer is too small for encoding\n");
> 
> Ditto.

I removed the mlog(..) call at both sites. Considering that one would
use the callpath to find out minimum required handle size, I guess we
don't want logging there.

> 
> > +		*max_len = 3;
> >  		type = 255;
> >  		goto bail;
> >  	}
> > diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
> > index a9cd507..acd0b2d 100644
> > --- a/include/linux/exportfs.h
> > +++ b/include/linux/exportfs.h
> > @@ -108,8 +108,10 @@ struct fid {
> >   *    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
> > + *    the filehandle fragment.  encode_fh() should return the fileid_type on
> > + *    success and on error returns 255 (if the space needed to encode fh is
> > + *    greater than @max_len*4 bytes). On error @max_len contain the minimum
> 
> s/contain/contains/.

Fixed


> 
> > + *    size(in 4 byte unit) needed to encode the file handle.
> >   *
> >   * fh_to_dentry:
> >   *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
> 


-aneesh
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