From: Neil Brown <neilb@suse.de>
To: "Balbir Singh" <bsingharora@gmail.com>
Cc: linux-kernel@vger.kernel.org, "Andrew Morton" <akpm@osdl.org>,
"Olaf Hering" <olh@suse.de>, "Jan Blunck" <jblunck@suse.de>,
"Kirill Korotaev" <dev@openvz.org>,
"Al Viro" <viro@ftp.linux.org.uk>
Subject: Re: [PATCH] Busy inodes after unmount, be more verbose in generic_shutdown_super
Date: Tue, 7 Mar 2006 12:58:20 +1100 [thread overview]
Message-ID: <17420.59580.915759.44913@cse.unsw.edu.au> (raw)
In-Reply-To: message from Balbir Singh on Monday March 6
On Monday March 6, bsingharora@gmail.com wrote:
> > Somewhere in among the comments (thanks), I realised that I was only
> > closing half the race. I had tried to make sure there were no stray
> > references to any dentries, but there is still the inode which is
> > being iput which can cause problem.
> >
> > The following patch takes a totally different approach, is based on an
> > idea from Jan Kara, and is much less intrusive.
> >
> > We:
> > - keep track of "who" is calling prune_dcache, and when a filesystem
> > is being unmounted (s_root == NULL) we only allow the unmount thread
> > to prune dentries.
> > - keep track of how many dentries are in the process of having
> > dentry_iput called on them for pruning
> > - don't allow umount to proceed until that count hits zero
> > - bias the count this way and that to make sure we get a wake_up at
> > the right time
> > - reuse 's_wait_unfrozen' to wait on the iput to complete.
> >
> > Again, I'm very keen on feedback. This race is very hard to trigger,
> > so code review is the only real way to evaluate that patch.
> >
> > Thanks,
> > NeilBrown
> >
>
> The code changes look big, have you looked at
> http://marc.theaimsgroup.com/?l=linux-kernel&m=113817279225962&w=2
No I haven't. I like it.
- Holding the semaphore shouldn't be a problem.
- calling down_read_trylock ought to be fast
- I *think* the unwanted calls to prune_dcache are always under
PF_MEMALLOC - they certainly seem to be.
And it is a nice small change.
Have you had any other feedback on this?
>
> Some top of the head feedback below. Will try and do a detailed review later.
>
> > + /* avoid further wakeups */
> > + sb->s_pending_iputs = 65000;
>
> This looks a bit ugly, what is 65000?
Just the first big number that came to by head... probably not needed.
NeilBrown
next prev parent reply other threads:[~2006-03-07 1:59 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-02 6:57 [PATCH] Busy inodes after unmount, be more verbose in generic_shutdown_super Neil Brown
2006-03-02 10:48 ` Jan Blunck
2006-03-03 11:42 ` Jan Blunck
2006-03-06 6:09 ` Neil Brown
2006-03-06 7:32 ` Balbir Singh
2006-03-07 1:58 ` Neil Brown [this message]
2006-03-07 2:49 ` Balbir Singh
2006-03-07 6:22 ` Kirill Korotaev
2006-03-07 6:16 ` Kirill Korotaev
2006-03-07 7:03 ` Balbir Singh
2006-03-07 7:21 ` Kirill Korotaev
2006-03-07 11:05 ` Balbir Singh
2006-03-08 0:29 ` Neil Brown
2006-03-08 2:17 ` Balbir Singh
2006-03-08 2:39 ` Neil Brown
2006-03-08 3:05 ` Balbir Singh
2006-03-08 11:01 ` Jan Blunck
2006-03-06 11:56 ` Jan Blunck
2006-03-07 2:15 ` Neil Brown
2006-03-06 11:56 ` Kirill Korotaev
2006-03-07 2:01 ` Neil Brown
2006-03-07 6:20 ` Kirill Korotaev
2006-03-07 23:20 ` Neil Brown
2006-03-09 12:03 ` Kirill Korotaev
-- strict thread matches above, loose matches on Subject: below --
2006-01-16 22:34 Olaf Hering
2006-01-16 23:23 ` Kirill Korotaev
2006-01-16 23:29 ` Olaf Hering
2006-01-17 2:05 ` Andrew Morton
2006-01-17 7:03 ` Kirill Korotaev
2006-01-18 22:49 ` Jan Blunck
2006-01-18 23:10 ` Andrew Morton
2006-01-19 10:08 ` Kirill Korotaev
2006-01-19 9:52 ` Kirill Korotaev
2006-01-19 10:04 ` Jan Blunck
2006-01-19 10:26 ` Kirill Korotaev
2006-01-20 19:06 ` Jan Blunck
2006-01-23 8:14 ` Kirill Korotaev
2006-01-30 11:54 ` Jan Blunck
2006-01-30 14:05 ` Kirill Korotaev
2006-01-30 14:21 ` Jan Blunck
2006-01-30 14:34 ` Kirill Korotaev
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