Re: [regression] fsnotify fails stress test since fsnotify_for_v5.15-rc1 merged

[Murphy Zhou <jencce.kernel@gmail.com>]

On Thu, Sep 09, 2021 at 01:14:05PM +0200, Petr Vorel wrote:
> > > On Tue, Sep 7, 2021 at 9:33 AM Murphy Zhou <jencce.kernel@gmail.com> wrote:
> 
> > > > Hi,
> 
> > > > Since this commit:
> 
> > > > commit ec44610fe2b86daef70f3f53f47d2a2542d7094f
> > > > Author: Amir Goldstein <amir73il@gmail.com>
> > > > Date:   Tue Aug 10 18:12:19 2021 +0300
> 
> > > >     fsnotify: count all objects with attached connectors
> 
> 
> 
> 
> > > > Kernel fsnotify can't finish a stress testcase that used to pass quickly.
> 
> > > > Kernel hung at umount. Can not be killed but restarting the server.
> 
> > > > Reproducer text is attached.
> 
> 
> > > Hi Murphy,
> 
> > > Thank you for the detailed report.
> > > I was able to reproduce the hang and the attached patch fixes it for me.
> > > Cloud you please verify the fix yourself as well?
> 
> > > This is a good regression test.
> > > Did you consider contributing it to LTP?
> > > I think the LTP team could also help converting your reproducer to
> > > an LTP test (CC: Petr).
> 
> > @Murphy: yes, please contribute that to LTP. There are already fanotify tests [1],
> > here is the C API [2] and shell API [3] (if needed, it should be enough to write
> > it just in C). If you have any questions, don't hesitate ask on LTP ML and Cc
> > me.
> 
> I see you've contributed to LTP already :).

Ya :) Thank you for the links. That's very helpful!

> 
> Kind regards,
> Petr
> 
> > @Amir: thanks!
> 
> > Kind regards,
> > Petr
> 
> > [1] https://github.com/linux-test-project/ltp/tree/master/testcases/kernel/syscalls/fanotify/
> > [2] https://github.com/linux-test-project/ltp/wiki/C-Test-API
> > [3] https://github.com/linux-test-project/ltp/wiki/Shell-Test-API
> 
> > > Thanks,
> > > Amir.
> 
> > > From 14d3c313062dfbc86b3d2c4d7deec56a096432f7 Mon Sep 17 00:00:00 2001
> > > From: Amir Goldstein <amir73il@gmail.com>
> > > Date: Thu, 9 Sep 2021 13:46:34 +0300
> > > Subject: [PATCH] fsnotify: fix sb_connectors leak
> 
> > > Fix a leak in s_fsnotify_connectors counter in case of a race between
> > > concurrent add of new fsnotify mark to an object.
> 
> > > The task that lost the race fails to drop the counter before freeing
> > > the unused connector.
> 
> > > Fixes: ec44610fe2b8 ("fsnotify: count all objects with attached connectors")
> > > Reported-by: Murphy Zhou <jencce.kernel@gmail.com>
> > > Link: https://lore.kernel.org/linux-fsdevel/20210907063338.ycaw6wvhzrfsfdlp@xzhoux.usersys.redhat.com/
> > > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > > ---
> > >  fs/notify/mark.c | 1 +
> > >  1 file changed, 1 insertion(+)
> 
> > > diff --git a/fs/notify/mark.c b/fs/notify/mark.c
> > > index 95006d1d29ab..fa1d99101f89 100644
> > > --- a/fs/notify/mark.c
> > > +++ b/fs/notify/mark.c
> > > @@ -531,6 +531,7 @@ static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
> > >  		/* Someone else created list structure for us */
> > >  		if (inode)
> > >  			fsnotify_put_inode_ref(inode);
> > > +		fsnotify_put_sb_connectors(conn);
> > >  		kmem_cache_free(fsnotify_mark_connector_cachep, conn);
> > >  	}

-- 
Murphy