linux-kernel - Re: [PATCH v5 1/4] fs: introduce helper d_path

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Message-ID: <YNRi5tZFjjpI2Fi3@smile.fi.intel.com>
Date:   Thu, 24 Jun 2021 13:48:06 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Jia He <justin.he@....com>, Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Eric Biggers <ebiggers@...gle.com>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Matthew Wilcox <willy@...radead.org>,
        Christoph Hellwig <hch@...radead.org>, nd@....com
Subject: Re: [PATCH v5 1/4] fs: introduce helper d_path_unsafe()

On Thu, Jun 24, 2021 at 11:26:53AM +0200, Petr Mladek wrote:
> On Tue 2021-06-22 17:36:39, Andy Shevchenko wrote:
> > On Tue, Jun 22, 2021 at 10:06:31PM +0800, Jia He wrote:
> > > This helper is similar to d_path() except that it doesn't take any
> > > seqlock/spinlock. It is typical for debugging purposes. Besides,
> > > an additional return value *prenpend_len* is used to get the full
> > > path length of the dentry, ingoring the tail '\0'.
> > > the full path length = end - buf - prepend_length - 1
> > 
> > Missed period at the end of sentence.
> > 
> > > Previously it will skip the prepend_name() loop at once in
> > > __prepen_path() when the buffer length is not enough or even negative.
> > > prepend_name_with_len() will get the full length of dentry name
> > > together with the parent recursively regardless of the buffer length.
> > 
> > > If someone invokes snprintf() with small but positive space,
> > > prepend_name_with_len() moves and copies the string partially.
> > > 
> > > More than that, kasprintf() will pass NULL _buf_ and _end_ as the
> > > parameters. Hence return at the very beginning with false in this case.
> > 
> > These two paragraphs are talking about printf() interface, while patch has
> > nothing to do with it. Please, rephrase in a way that it doesn't refer to the
> > particular callers. Better to mention them in the corresponding printf()
> > patch(es).
> 
> The two paragraphs are actually repeated in the 2nd
> patch. Unfortunately, they do not make sense there either because they
> comment code that is modified in this patch.
> 
> We could describe it here a generic way. For example:
> 
>   prepend_name_with_len() moves and copies the path when the given
>   buffer is not big enough. It cuts off the end of the path.
>   It returns immediately when there is no buffer at all.

Yes, that's my point, but sorry if I made it unclear.

-- 
With Best Regards,
Andy Shevchenko