linux-kernel - Re: [PATCH 3/5] proc: Remove the hard coded inode numbers.

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Message-Id: <20060907110659.373d6f2b.akpm@osdl.org>
Date:	Thu, 7 Sep 2006 11:06:59 -0700
From:	Andrew Morton <akpm@...l.org>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] proc: Remove the hard coded inode numbers.

On Thu, 07 Sep 2006 11:55:59 -0600
ebiederm@...ssion.com (Eric W. Biederman) wrote:

> Andrew Morton <akpm@...l.org> writes:
> 
> > On Wed, 06 Sep 2006 10:27:13 -0600
> > ebiederm@...ssion.com (Eric W. Biederman) wrote:
> >
> >> +static int proc_fill_cache(struct file *filp, void *dirent, filldir_t
> > filldir,
> >> +	char *name, int len,
> >> +	instantiate_t instantiate, struct task_struct *task, void *ptr)
> >> +{
> >> +	struct dentry *child, *dir = filp->f_dentry;
> >> +	struct inode *inode;
> >> +	struct qstr qname;
> >> +	ino_t ino = 0;
> >> +	unsigned type = DT_UNKNOWN;
> >> +
> >> +	qname.name = name;
> >> +	qname.len  = len;
> >> +	qname.hash = full_name_hash(name, len);
> >> +
> >> +	child = d_lookup(dir, &qname);
> >> +	if (!child) {
> >> +		struct dentry *new;
> >> +		new = d_alloc(dir, &qname);
> >> +		if (new) {
> >> +			child = instantiate(dir->d_inode, new, task, ptr);
> >> +			if (child)
> >> +				dput(new);
> >> +			else
> >> +				child = new;
> >> +		}
> >> +	}
> >> +	if (!child || IS_ERR(child) || !child->d_inode)
> >> +		goto end_instantiate;
> >> +	inode = child->d_inode;
> >> +	if (inode) {
> >> +		ino = inode->i_ino;
> >> +		type = inode->i_mode >> 12;
> >> +	}
> >> +	dput(child);
> >> +end_instantiate:
> >> +	if (!ino)
> >> +		ino = find_inode_number(dir, &qname);
> >> +	if (!ino)
> >> +		ino = 1;
> >> +	return filldir(dirent, name, len, filp->f_pos, ino, type);
> >> +}
> >
> > The error handling in here looks rather absent.
> 
> Hey, thanks for the review.
> 
> I don't think so but a comment or two might be in order.
> 
> Calling filldir with the filename is the important part,
> and the only real error is if filldir fails.
> 
> The rest of the logic is about populating and querying the
> dcache so we can find our real inode number, if every reasonable
> attempt to perform a dcache lookup fails I simply set the inode
> number to 1 and use that in filldir.  It's wrong but at least
> I report the file is there.
> 
> If I can find the dentry I lookup the inode and the inode
> number and file type, and the dput the dentry.
> 
> If I can't lookup the dentry I attempt to create it.
> instantiate will return a dentry or NULL if the dentry I preallocate
> for it is good enough.

I suspected it was something like that.

> Is there something specific you are not seeing?

Code comments explaining this stuff ;)
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