From: Kent Overstreet <kent.overstreet@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Dave Chinner <dchinner@redhat.com>,
darrick.wong@oracle.com, tytso@mit.edu,
linux-btrfs@vger.kernel.org, clm@fb.com, jbacik@fb.com,
viro@zeniv.linux.org.uk, willy@infradead.org
Subject: Re: [PATCH 04/10] locking: export osq_lock()/osq_unlock()
Date: Fri, 18 May 2018 07:32:05 -0400 [thread overview]
Message-ID: <20180518113205.GA16943@kmo-pixel> (raw)
In-Reply-To: <20180518110808.GH12217@hirez.programming.kicks-ass.net>
On Fri, May 18, 2018 at 01:08:08PM +0200, Peter Zijlstra wrote:
> On Fri, May 18, 2018 at 06:18:04AM -0400, Kent Overstreet wrote:
> > On Fri, May 18, 2018 at 11:52:04AM +0200, Peter Zijlstra wrote:
> > > On Fri, May 18, 2018 at 03:49:06AM -0400, Kent Overstreet wrote:
> > >
> > > No.. and most certainly not without a _very_ good reason.
> >
> > Ok, can I ask why?
>
> Because it is an internal helper for lock implementations that want to
> do optimistic spinning, it isn't a lock on its own and lacks several
> things you would expect.
>
> Using it is tricky and I don't trust random module authors to get 1+1
> right, let alone use this thing correctly (no judgement on your code,
> just in general).
Yeah, that's true. I just modelled my usage on the rwsem code.
It does strike me that the whole optimistic spin algorithm
(mutex_optimistic_spin() and rwsem_optimistic_spin()) are ripe for factoring
out. They've been growing more optimizations I see, and the optimizations mostly
aren't specific to either locks.
> > Here's what it's for:
>
> I'll try and have a look soon :-) But does that really _have_ to live in
> a module?
No, I'd be completely fine with moving six locks out of bcachefs, just don't
know that there'd be any other users. But I suppose we do have other filesystems
that use btrees, and that's what they're for.
next prev parent reply other threads:[~2018-05-18 11:32 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-18 7:48 [PATCH 00/10] RFC: assorted bcachefs patches Kent Overstreet
2018-05-18 7:49 ` [PATCH 01/10] mm: pagecache add lock Kent Overstreet
2018-05-18 13:13 ` Matthew Wilcox
2018-05-18 15:53 ` Christoph Hellwig
2018-05-18 17:45 ` Kent Overstreet
2018-05-23 23:55 ` Notes on locking for pagacache consistency (was: [PATCH 01/10] mm: pagecache add lock) Kent Overstreet
2018-05-20 22:45 ` [PATCH 01/10] mm: pagecache add lock Kent Overstreet
2018-05-23 15:22 ` Christoph Hellwig
2018-05-23 17:12 ` Kent Overstreet
2018-05-18 7:49 ` [PATCH 02/10] mm: export find_get_pages() Kent Overstreet
2018-05-18 16:00 ` Christoph Hellwig
2018-05-18 7:49 ` [PATCH 03/10] locking: bring back lglocks Kent Overstreet
2018-05-18 9:51 ` Peter Zijlstra
2018-05-18 10:13 ` Kent Overstreet
2018-05-18 11:03 ` Peter Zijlstra
2018-05-18 11:39 ` Kent Overstreet
2018-05-18 7:49 ` [PATCH 04/10] locking: export osq_lock()/osq_unlock() Kent Overstreet
2018-05-18 9:52 ` Peter Zijlstra
2018-05-18 10:18 ` Kent Overstreet
2018-05-18 11:08 ` Peter Zijlstra
2018-05-18 11:32 ` Kent Overstreet [this message]
2018-05-18 11:40 ` Peter Zijlstra
2018-05-18 12:40 ` Kent Overstreet
2018-05-18 7:49 ` [PATCH 05/10] don't use spin_lock_irqsave() unnecessarily Kent Overstreet
2018-05-18 16:01 ` Christoph Hellwig
2018-05-18 7:49 ` [PATCH 06/10] Generic radix trees Kent Overstreet
2018-05-18 16:02 ` Christoph Hellwig
2018-05-18 17:38 ` Kent Overstreet
2018-05-18 7:49 ` [PATCH 07/10] bcache: optimize continue_at_nobarrier() Kent Overstreet
2018-05-18 7:49 ` [PATCH 08/10] bcache: move closures to lib/ Kent Overstreet
2018-05-18 16:02 ` Christoph Hellwig
2018-05-18 7:49 ` [PATCH 09/10] closures: closure_wait_event() Kent Overstreet
2018-05-18 7:49 ` [PATCH 10/10] Dynamic fault injection Kent Overstreet
2018-05-18 16:02 ` Christoph Hellwig
2018-05-18 17:37 ` Kent Overstreet
2018-05-18 19:05 ` Andreas Dilger
2018-05-18 19:10 ` Kent Overstreet
2018-05-18 20:54 ` Andreas Dilger
2018-05-18 7:55 ` [PATCH 00/10] RFC: assorted bcachefs patches Kent Overstreet
2018-05-18 17:45 ` Josef Bacik
2018-05-18 17:49 ` Kent Overstreet
2018-05-18 18:03 ` Josef Bacik
2018-05-18 18:28 ` Kent Overstreet
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