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Subject: Re: WARNING: CPU: 1 PID: 14735 at fs/dcache.c:365
 dentry_free+0x100/0x128
From:   Sam James <sam@gentoo.org>
In-Reply-To: <Ytg2CDLzLo+FKbTZ@ZenIV>
Date:   Thu, 21 Jul 2022 00:15:43 +0100
Cc:     Hillf Danton <hdanton@sina.com>, Helge Deller <deller@gmx.de>,
        John David Anglin <dave.anglin@bell.net>,
        linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Message-Id: <9B4CB715-FEA1-4991-ABA1-23B2DF203258@gentoo.org>
References: <20220709090756.2384-1-hdanton@sina.com>
 <20220715133300.1297-1-hdanton@sina.com>
 <cff76e00-3561-4069-f5c7-26d3de4da3c4@gmx.de> <Ytd2g72cj0Aq1MBG@ZenIV>
 <860792bb-1fd6-66c6-ef31-4edd181e2954@gmx.de> <YtepmwLj//zrD3V3@ZenIV>
 <20220720110032.1787-1-hdanton@sina.com> <Ytg2CDLzLo+FKbTZ@ZenIV>
To:     Al Viro <viro@zeniv.linux.org.uk>, Helge Deller <deller@gmx.de>
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> On 20 Jul 2022, at 18:06, Al Viro <viro@zeniv.linux.org.uk> wrote:
> 
> On Wed, Jul 20, 2022 at 07:00:32PM +0800, Hillf Danton wrote:
> 
>> To help debug it, de-union d_in_lookup_hash with d_alias and add debug
>> info after dentry is killed. If any warning hits, we know where to add
>> something like
>> 
>> 	WARN_ON(dentry->d_flags & DCACHE_DENTRY_KILLED);
>> 
>> before hlist_bl_add or hlist_add.

> [snip]
> I wonder if anyone had seen anything similar outside of parisc...
> I don't know if I have any chance to reproduce it here - the only
> parisc box I've got is a 715/100 (assuming the disk is still alive)
> and it's 32bit, unlike the reported setups and, er, not fast.
> qemu seems to have some parisc support, but it's 32bit-only at the
> moment...

I don't think I've seen this on parisc either, but I don't think
I've used tmpfs that heavily. I'll try it in case it's somehow more
likely to trigger it.

Helge, were there any particular steps to reproduce this? Or just
start doing your normal Debian builds on a tmpfs and it happens
soon enough?


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