From: Matthew Wilcox <willy@infradead.org>
To: Justin He <Justin.He@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Petr Mladek <pmladek@suse.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Jonathan Corbet <corbet@lwn.net>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Luca Coelho <luciano.coelho@intel.com>,
Kalle Valo <kvalo@codeaurora.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Johannes Berg <johannes.berg@intel.com>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>
Subject: Re: [PATCH RFCv2 2/3] lib/vsprintf.c: make %pD print full path for file
Date: Fri, 28 May 2021 16:22:16 +0100 [thread overview]
Message-ID: <YLEKqGkm8bX6LZfP@casper.infradead.org> (raw)
In-Reply-To: <AM6PR08MB437615DB6A6DEC33223A3138F7229@AM6PR08MB4376.eurprd08.prod.outlook.com>
On Fri, May 28, 2021 at 03:09:28PM +0000, Justin He wrote:
> > I'm not sure why it's so complicated. p->len records how many bytes
> > are needed for the entire path; can't you just return -p->len ?
>
> prepend_name() will return at the beginning if p->len is <0 in this case,
> we can't even get the correct full path size if keep __prepend_path unchanged.
> We need another new helper __prepend_path_size() to get the full path size
> regardless of the negative value p->len.
It's a little hard to follow, based on just the patches. Is there a
git tree somewhere of Al's patches that you're based on?
Seems to me that prepend_name() is just fine because it updates p->len
before returning false:
static bool prepend_name(struct prepend_buffer *p, const struct qstr *name)
{
const char *dname = smp_load_acquire(&name->name); /* ^^^ */
u32 dlen = READ_ONCE(name->len);
char *s;
p->len -= dlen + 1;
if (unlikely(p->len < 0))
return false;
I think the only change you'd need to make for vsnprintf() is in
prepend_path():
- if (!prepend_name(&b, &dentry->d_name))
- break;
+ prepend_name(&b, &dentry->d_name);
Would that hurt anything else?
> More than that, even the 1st vsnprintf could have _end_ > _buf_ in some case:
> What if printk("%pD", filp) ? The 1st vsnprintf has positive (end-buf).
I don't understand the problem ... if p->len is positive, then you
succeeded. if p->len is negative then -p->len is the expected return
value from vsnprintf(). No?
next prev parent reply other threads:[~2021-05-28 15:23 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-28 11:39 [PATCH RFCv2 0/3] make '%pD' print full path for file Jia He
2021-05-28 11:39 ` [PATCH RFCv2 1/3] fs: introduce helper d_path_fast() Jia He
2021-05-28 12:44 ` Al Viro
2021-05-28 12:51 ` Matthew Wilcox
2021-05-28 14:23 ` Justin He
2021-05-28 11:39 ` [PATCH RFCv2 2/3] lib/vsprintf.c: make %pD print full path for file Jia He
2021-05-28 12:59 ` Matthew Wilcox
2021-05-28 14:22 ` Justin He
2021-05-28 14:52 ` Matthew Wilcox
2021-05-28 15:09 ` Justin He
2021-05-28 15:22 ` Matthew Wilcox [this message]
2021-05-31 0:39 ` Justin He
2021-06-01 14:42 ` Justin He
2021-06-01 15:30 ` Matthew Wilcox
2021-06-01 15:36 ` Andy Shevchenko
2021-06-01 15:44 ` Matthew Wilcox
2021-06-01 15:53 ` Andy Shevchenko
2021-06-01 16:10 ` Andy Shevchenko
2021-06-01 17:05 ` Matthew Wilcox
2021-06-01 19:01 ` Rasmus Villemoes
2021-06-02 5:47 ` Justin He
2021-05-28 20:06 ` Rasmus Villemoes
2021-05-30 15:18 ` Matthew Wilcox
2021-05-31 9:40 ` Petr Mladek
2021-05-28 11:39 ` [PATCH RFCv2 3/3] s390/hmcdrv: remove the redundant directory path in debug message Jia He
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