RE: [PATCH 09/14] d_path: introduce struct prepend_buffer

From: Justin He <Justin.He@arm.com>
To: "Enrico Weigelt, metux IT consult" <lkml@metux.net>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Linus Torvalds <torvalds@linux-foundation.org>
Cc: 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>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Ira Weiny <ira.weiny@intel.com>,
	Eric Biggers <ebiggers@google.com>,
	"Ahmed S. Darwish" <a.darwish@linutronix.de>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-s390 <linux-s390@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>, nd <nd@arm.com>
Subject: RE: [PATCH 09/14] d_path: introduce struct prepend_buffer
Date: Fri, 25 Jun 2021 00:43:22 +0000	[thread overview]
Message-ID: <AM0PR08MB4370B5A85FFDD36D79DE73E2F7069@AM0PR08MB4370.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <f9908c77-77e2-03fd-25a4-f7ce9802535e@metux.net>

Hi Enrico

> -----Original Message-----
> From: Enrico Weigelt, metux IT consult <lkml@metux.net>
> Sent: Thursday, June 24, 2021 5:30 PM
> To: Justin He <Justin.He@arm.com>; Al Viro <viro@zeniv.linux.org.uk>; Linus
> Torvalds <torvalds@linux-foundation.org>
> Cc: 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>; Heiko
> Carstens <hca@linux.ibm.com>; Vasily Gorbik <gor@linux.ibm.com>; Christian
> Borntraeger <borntraeger@de.ibm.com>; Eric W . Biederman
> <ebiederm@xmission.com>; Darrick J. Wong <darrick.wong@oracle.com>; Peter
> Zijlstra (Intel) <peterz@infradead.org>; Ira Weiny <ira.weiny@intel.com>;
> Eric Biggers <ebiggers@google.com>; Ahmed S. Darwish
> <a.darwish@linutronix.de>; open list:DOCUMENTATION <linux-
> doc@vger.kernel.org>; Linux Kernel Mailing List <linux-
> kernel@vger.kernel.org>; linux-s390 <linux-s390@vger.kernel.org>; linux-
> fsdevel <linux-fsdevel@vger.kernel.org>
> Subject: Re: [PATCH 09/14] d_path: introduce struct prepend_buffer
> 
> Hi folks,
> 
> <snip>
> 
> >>         We've a lot of places where we have pairs of form (pointer to
> end
> >> of buffer, amount of space left in front of that).  These sit in pairs
> of
> >> variables located next to each other and usually passed by reference.
> >> Turn those into instances of new type (struct prepend_buffer) and pass
> >> reference to the pair instead of pairs of references to its fields.
> >>
> >> Declared and initialized by DECLARE_BUFFER(name, buf, buflen).
> >>
> >> extract_string(prepend_buffer) returns the buffer contents if
> >> no overflow has happened, ERR_PTR(ENAMETOOLONG) otherwise.
> >> All places where we used to have that boilerplate converted to use
> >> of that helper.
> 
> this smells like a generic enough thing to go into lib, doesn't it ?
> 
Maybe, but the struct prepend_buffer also needs to be moved into lib.
Is it necessary? Is there any other user of struct prepend_buffer?

--
Cheers,
Justin (Jia He)