From: Arnd Bergmann <arnd@arndb.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: viro@zeniv.linux.org.uk, hch@infradead.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 1/5] VFS: Do (nearly) lockless generic_file_llseek
Date: Fri, 17 Jun 2011 23:18:38 +0200 [thread overview]
Message-ID: <201106172318.38338.arnd@arndb.de> (raw)
In-Reply-To: <20110617174239.GG16236@one.firstfloor.org>
On Friday 17 June 2011 19:42:39 Andi Kleen wrote:
> On Fri, Jun 17, 2011 at 02:40:14PM +0200, Arnd Bergmann wrote:
> > On Thursday 16 June 2011 23:07:18 Andi Kleen wrote:
> > > So still need a lock, but can use a cheap local one.
> > >
> > > This patch implements this new scheme in generic_file_llseek.
> > > I dropped generic_file_llseek_unlocked and changed all callers.
> >
> > What about default_llseek? If you change generic_file_llseek, you should
> > probably change that, too.
>
> That's used by a lot of drivers, and since I cannot audit them
> all I chose to be conservative. not sure it's ever performance
> critical anyways?
Probably not. Note that all uses of default_llseek were introduced
in the conversion from an implicit default_llseek when they did not
set the operation before the BKL conversion. There were also patches
floating around to merge generic_file_llseek and default_llseek.
There was not a single case of a driver that relied on the BKL to
lock against default_llseek before I changed it to i_mutex.
Arnd
prev parent reply other threads:[~2011-06-17 21:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-16 21:07 [PATCH 1/5] VFS: Do (nearly) lockless generic_file_llseek Andi Kleen
2011-06-16 21:07 ` [PATCH 2/5] VFS: Use f_lock for SEEK_SET Andi Kleen
2011-06-16 21:07 ` [PATCH 3/5] VFS: Add generic_file_llseek_size Andi Kleen
2011-06-16 21:07 ` [PATCH 4/5] EXT4: Replace cut'n'pasted llseek code with generic_file_llseek_size Andi Kleen
2011-06-16 21:07 ` [PATCH 5/5] NFS: Drop unnecessary locking in llseek Andi Kleen
2011-06-17 12:40 ` [PATCH 1/5] VFS: Do (nearly) lockless generic_file_llseek Arnd Bergmann
2011-06-17 17:42 ` Andi Kleen
2011-06-17 21:18 ` Arnd Bergmann [this message]
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