linux-kernel - Re: [PATCH] Fix d_path for lazy unmounts

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Message-Id: <200702141843.49668.agruen@suse.de>
Date:	Wed, 14 Feb 2007 18:43:49 -0800
From:	Andreas Gruenbacher <agruen@...e.de>
To:	Neil Brown <neilb@...e.de>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...l.org>, Tony Jones <tonyj@...e.de>
Subject: Re: [PATCH] Fix d_path for lazy unmounts

On Sunday 04 February 2007 16:15, Neil Brown wrote:
> The behaviour in the face of a lazy unmount should be clarified in
> this comment.

Done.

> If sys_getcwd is called on a directory that is no longer
> connected to the root, it isn't clear to me that it should return
> without an error.
> Without your patch it can return garbage which is clearly wrong.
> With you patch it will return a relative path name, which is also
> wrong (it isn't a valid path that leads to the current working directory).

Right, it should return -ENOENT instead in that case. Fixed as well.

> I would suggest that 'fail_deleted' be (e.g.) changed to
> 'fail_condition' where two conditions are defined
> #define DPATH_FAIL_DELETED 1
> #define DPATH_FAIL_DISCONNECTED 2

The much cleaner interface is to check if the path returned starts with a 
slash. If it doesn't, we know the path is bad as far as sys_getcwd() is 
concerned. We will construct the partial path in __d_path before figuring out 
that the path is disconnected, so no performance penalty, either.

> In reality, you are comparing "buflen < namelen+1" but spelling it as
> "buflen <= namelen".  I would prefer the full spelling with least room
> for confusion.

I'm fine either way.

> Maybe:
> > +		buflen -= namelen + 1;
> > +		buffer -= namelen + 1;
> > +		memcpy(buffer+1, dentry->d_name.name, namelen);
> > +		*buffer = '/';

That's better, yes.

Thanks,
Andreas
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