From: Jan Kara <jack@suse.cz>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Jan Kara <jack@suse.cz>, Al Viro <viro@zeniv.linux.org.uk>,
Dave Chinner <david@fromorbit.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 7/8] shift percpu_counter_destroy() into destroy_super_work()
Date: Thu, 13 Aug 2015 16:09:29 +0200 [thread overview]
Message-ID: <20150813140929.GA4392@quack.suse.cz> (raw)
In-Reply-To: <20150813133616.GC15609@redhat.com>
On Thu 13-08-15 15:36:16, Oleg Nesterov wrote:
> On 08/13, Jan Kara wrote:
> >
> > On Tue 11-08-15 19:04:16, Oleg Nesterov wrote:
> > >
> > > So this is just the temporary kludge which helps us to avoid the
> > > conflicts with the changes which will be (hopefully) routed via
> > > rcu tree.
> > >
> > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> >
> > Looking into this again, it would seem somewhat cleaner to me to move the
> > destruction to deactivate_locked_super() instead.
>
> Heh ;) You know, I was looking at deactivate_locked_super(). However, I
> simply do not understand this code enough, I failed to verify it would
> be safe to destroy s_writers there.
Yes, it will be safe. After ->kill_sb() callback the filesystem is dead.
There can be someone still holding reference to superblock but these are
just users inspecting the structure definitely not caring about freeze
protection.
> And. Please note destroy_super() in alloc_super() error path, so this
> needs a bit more changes in any case.
Yes. But you can sleep in alloc_super() so that would be easy enough.
> Can't we live with this hack for now? To remind, it will be reverted
> (at least partially) in any case. Yes, yes, it is very ugly and the
> changelog documents this fact. But it looks simple and safe. To me
> it would be better to make the conversion first, then cleanup this
> horror after another discussion.
All I care about is that long-term, all handling from destroy_super() that
needs to sleep ends up in one place. So if you promise you'll make this
happen I can live with the workqueue solution for now (but you have to
convince also Al as a maintainer ;).
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2015-08-13 14:09 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-11 17:03 [PATCH v2 0/8] change sb_writers to use percpu_rw_semaphore Oleg Nesterov
2015-08-11 17:03 ` [PATCH v2 1/8] introduce __sb_{acquire,release}_write() helpers Oleg Nesterov
2015-08-13 9:45 ` Jan Kara
2015-08-13 9:56 ` Jan Kara
2015-08-13 13:17 ` Oleg Nesterov
2015-08-13 13:32 ` Jan Kara
2015-08-13 13:37 ` Oleg Nesterov
2015-08-11 17:04 ` [PATCH v2 2/8] fix the broken lockdep logic in __sb_start_write() Oleg Nesterov
2015-08-13 10:02 ` Jan Kara
2015-08-13 13:22 ` Oleg Nesterov
2015-08-13 13:29 ` Jan Kara
2015-08-11 17:04 ` [PATCH v2 3/8] document rwsem_release() in sb_wait_write() Oleg Nesterov
2015-08-13 10:22 ` Jan Kara
2015-08-11 17:04 ` [PATCH v2 4/8] percpu-rwsem: introduce percpu_down_read_trylock() Oleg Nesterov
2015-08-11 17:04 ` [PATCH v2 5/8] percpu-rwsem: introduce percpu_rwsem_release() and percpu_rwsem_acquire() Oleg Nesterov
2015-08-11 17:04 ` [PATCH v2 6/8] percpu-rwsem: kill CONFIG_PERCPU_RWSEM Oleg Nesterov
2015-08-11 17:04 ` [PATCH v2 7/8] shift percpu_counter_destroy() into destroy_super_work() Oleg Nesterov
2015-08-13 10:35 ` Jan Kara
2015-08-13 13:36 ` Oleg Nesterov
2015-08-13 14:09 ` Jan Kara [this message]
2015-08-13 15:20 ` Oleg Nesterov
2015-08-11 17:04 ` [PATCH v2 8/8] change sb_writers to use percpu_rw_semaphore Oleg Nesterov
2015-08-13 10:48 ` Jan Kara
2015-08-12 13:11 ` [PATCH v2 9/8] don't fool lockdep in freeze_super() and thaw_super() paths Oleg Nesterov
2015-08-13 11:01 ` Jan Kara
2015-08-13 13:58 ` Oleg Nesterov
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