From: Arnd Bergmann <arnd@arndb.de>
To: Jan Blunck <jblunck@suse.de>
Cc: "Jamie Lokier" <jamie@shareable.org>,
linux-fsdevel@vger.kernel.org,
"Christoph Hellwig" <hch@infradead.org>,
"Alan Cox" <alan@lxorguk.ukuu.org.uk>,
"Linux-Kernel Mailinglist" <linux-kernel@vger.kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
jkacur@redhat.com, "Frédéric Weisbecker" <fweisbec@gmail.com>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Matthew Wilcox" <matthew@wil.cx>
Subject: Re: [PATCH 01/15] Introduce noop_llseek()
Date: Sat, 21 Nov 2009 17:56:27 +0100 [thread overview]
Message-ID: <200911211756.27596.arnd@arndb.de> (raw)
In-Reply-To: <20091120171107.GZ21750@bolzano.suse.de>
On Friday 20 November 2009, Jan Blunck wrote:
> On Fri, Nov 20, Jamie Lokier wrote:
>
> > Jan Blunck wrote:
> > > The noop_llseek() is a llseek() operation that filesystems can use that
> > > don't want to support seeking (leave the file->f_pos untouched) but still
> > > want to let the syscall itself to succeed.
> >
> > This is weird behaviour: if you want to allow llseek() to succeed but
> > don't really support seeking, why does the device even care about the
> > value of file->f_pos?
>
> The device itself does not care about it but it is userspace that is expecting
> the seek to succeed. There is a comment in osst that at least there seems to
> be a borken version of tar that wants to seek on the device even it that does
> not have any effect.
Looking at the question from the other side -- if the device and the user
don't care about file->f_pos, what's wrong with calling generic_file_llseek
instead of noop_llseek?
Arnd <><
next prev parent reply other threads:[~2009-11-21 16:56 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-20 16:40 [PATCH 00/15] Remove BKL from default_llseek() and other issues (v2) Jan Blunck
2009-11-20 16:40 ` [PATCH 01/15] Introduce noop_llseek() Jan Blunck
2009-11-20 17:05 ` Jamie Lokier
2009-11-20 17:11 ` Jan Blunck
2009-11-21 16:56 ` Arnd Bergmann [this message]
2009-11-20 16:40 ` [PATCH 02/15] osst: Use noop_llseek() instead of default_llseek() Jan Blunck
2009-11-20 17:09 ` Jamie Lokier
2009-11-20 17:25 ` Jan Blunck
2009-11-20 16:40 ` [PATCH 03/15] osst: Update ppos instead of using file->f_pos Jan Blunck
2009-11-20 17:13 ` Jamie Lokier
2009-11-20 17:16 ` Jamie Lokier
2009-11-20 16:40 ` [PATCH 04/15] s390: tape_char should update " Jan Blunck
2009-11-20 16:40 ` [PATCH 05/15] flash_read should update ppos instead of file->f_pos Jan Blunck
2009-11-20 16:40 ` [PATCH 06/15] eeprom_read()/eeprom_write() " Jan Blunck
2009-11-20 16:40 ` [PATCH 07/15] sched_feat_write: Update " Jan Blunck
2009-11-23 18:54 ` [tip:sched/core] sched_feat_write(): " tip-bot for Jan Blunck
2009-11-20 16:40 ` [PATCH 08/15] airo: Use " Jan Blunck
2009-11-20 16:40 ` [PATCH 09/15] frv: remove "struct file *" argument from sysctl ->proc_handler Jan Blunck
2009-11-20 16:40 ` [PATCH 10/15] mISDN: Remove unnecessary test on f_pos Jan Blunck
2009-11-20 16:40 ` [PATCH 11/15] zcrypt: Use nonseekable_open() Jan Blunck
2009-11-20 16:40 ` [PATCH 12/15] rtc-m41t80: " Jan Blunck
2009-11-20 16:40 ` [PATCH 13/15] Do not fallback to default_llseek() when readdir() uses BKL Jan Blunck
2009-11-20 21:27 ` Jan Kara
2009-11-21 18:03 ` Anders Larsen
2009-11-20 16:40 ` [PATCH 14/15] BKL: Remove BKL from default_llseek() Jan Blunck
2009-11-20 16:40 ` [PATCH 15/15] BKL: Update documentation on llseek( \b) Jan Blunck
2009-11-20 17:02 ` [PATCH 15/15] BKL: Update documentation on llseek(\b) Alan Cox
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