From: Arnd Bergmann <arnd@arndb.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Matthew Wilcox <willy@linux.intel.com>,
Christoph Hellwig <hch@lst.de>,
Trond Myklebust <trond.myklebust@fys.uio.no>,
"J. Bruce Fields" <bfields@fieldses.org>,
Miklos Szeredi <mszeredi@suse.cz>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>, John Kacur <jkacur@redhat.com>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] Remove BKL from fs/locks.c
Date: Tue, 14 Sep 2010 22:39:02 +0200 [thread overview]
Message-ID: <201009142239.02904.arnd@arndb.de> (raw)
In-Reply-To: <AANLkTimzFDdWbr2gtfmJmfGJVnyURcpvwnGf334ZHVYc@mail.gmail.com>
On Tuesday 14 September 2010 22:20:22 Linus Torvalds wrote:
> End result: anybody who uses the old exports will just not link at
> all, and all in-kernel users (ie lockd etc) will now very explicitly
> have that xyz_bkl() use.
>
> After that one release, we can re-introduce the old names without the
> bkl, and let filesystems and other subsystems just decide that they
> don't want the bkl version one by one. So that first phase would be
> basically a no-op with an interface rename just so that the rest could
> then be done piece-meal.
Hmm, maybe I'm misunderstanding part of that plan, but I think it
won't work because the BKL in there seems to protect all struct file_lock
instances and they are passed around to other code, most importantly
lockd. The file_locks themselves can be accessed both using sys_flock()
etc locally and using afs/nfs/coda/... exported file systems from other
systems.
AFAICT we could end up with lockd changing data under BKL while a sys_flock()
accesses the same data under file_lock_lock, with no mutual exclusion
between the two.
Arnd
next prev parent reply other threads:[~2010-09-14 20:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-14 20:06 [PATCH] Remove BKL from fs/locks.c Arnd Bergmann
2010-09-14 20:20 ` Linus Torvalds
2010-09-14 20:39 ` Arnd Bergmann [this message]
2010-09-14 20:53 ` Linus Torvalds
2010-09-14 21:24 ` Arnd Bergmann
2010-09-14 21:55 ` Trond Myklebust
2010-09-15 16:30 ` Arnd Bergmann
2010-09-15 17:02 ` Sage Weil
2010-09-15 17:17 ` Arnd Bergmann
2010-09-15 18:22 ` Sage Weil
2010-09-15 20:42 ` J. Bruce Fields
2010-09-16 8:28 ` Arnd Bergmann
2010-09-16 14:10 ` J. Bruce Fields
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