linux-ext4 - Re: [patch 4/4] fs: jbd/jbd2: Substitute BH locks for RT and lock debugging

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Date:   Thu, 1 Aug 2019 10:44:12 +0200
From:   Jan Kara <jack@...e.cz>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Jan Kara <jack@...e.cz>, LKML <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Theodore Tso <tytso@....edu>, Julia Cartwright <julia@...com>,
        Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [patch 4/4] fs: jbd/jbd2: Substitute BH locks for RT and lock
 debugging

On Wed 31-07-19 21:40:42, Thomas Gleixner wrote:
> On Wed, 31 Jul 2019, Jan Kara wrote:
> > BH_State lock is definitely worth it. In fact, if you placed the spinlock
> > inside struct journal_head (which is the structure whose members are in
> > fact protected by it), I'd be even fine with just using the spinlock always
> > instead of the bit spinlock. journal_head is pretty big anyway (and there's
> > even 4-byte hole in it for 64-bit archs) and these structures are pretty
> > rare (only for actively changed metadata buffers).
> 
> Just need to figure out what to do with the ASSERT_JH(state_is_locked) case for
> UP. Perhaps just return true for UP && !DEBUG_SPINLOCK?

Yes, that makes sense.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR