linux-kernel - Re: [PATCH 1/8] vfs - change d_manage() to take a struct path

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Date:   Thu, 27 Oct 2016 14:50:28 +0800
From:   Ian Kent <raven@...maw.net>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        autofs mailing list <autofs@...r.kernel.org>,
        Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Omar Sandoval <osandov@...ndov.com>
Subject: Re: [PATCH 1/8] vfs - change d_manage() to take a struct path

On Thu, 2016-10-27 at 10:47 +0800, Ian Kent wrote:
> On Thu, 2016-10-27 at 03:11 +0100, Al Viro wrote:
> > 
> > 
> > How much testing did it get?  I've several test setups involving
> > autofs, but they are nowhere near exhaustive and I don't have good
> > enough feel of the codebase to slap together something with decent
> > coverage...
> It got my standard testing.
> 
> For that I use a modified version of the autofs Connectathon system.
> 
> It's more about testing a wide variety of syntax and map setups and so
> exercises
> a large number of different types of autofs mounts.
> 
> It's meant to check normal operation but not so much stress testing even
> though
> it does perform quite a few mounts (around 250-300, not to mention the autofs
> mounts themselves).
> 
> I have another standard test I call the submount-test and it was originally
> done
> to stress test the most common problem I see, concurrent expire to mount.
> 
> I didn't see any problems I couldn't explain in these but I might need to re-
> visit the submount-test to see if it is still doing what I want.
> 
> OTOH, the pattern of mount and umount I see when the submount-test is run does
> look like it is doing what I want but it might not be getting all the way to
> the
> top of the tree of mounts enough times over the course of the test.
> 
> So I'm happy with my testing, just not as happy as I could be.

Well, almost happy with my testing.

Naturally I also tested the specific case this series is meant to fix.

Basically:
ls /mnt/foo            # do the initial automount
unshare -m sleep 10 &  # hold the automount in a new namespace
umount /mnt/foo        # pretend the mount timed out
ls /mnt/foo            # try to access it again
ls: cannot open directory '/mnt/foo': Too many levels of symbolic links

as seen on the autofs mailing list. My specific test was a little different but
verified this was resolved.

Now that Al seems reasonably OK with the series, with some changes, I'll test
some other use cases, mainly to verify the expire still functions as required.
That might need more work.

Ian