[OpenWrt-Devel] Device tree issues with TL-WDR4900 (mpc85xx) and kernel 4.0.1

[Wojciech Dubowik]

On 07/05/15 14:49, Felix Fietkau wrote:
> On 2015-05-07 08:01, Wojciech Dubowik wrote:
>> Try to boot with kernel locking enabled. I have seen jffs2 deadlocks on
>> readdir. As far as I remember
>> with this patch it went through but I don't know anymore whether I have
>> changed sth in config.
>>
>> Have a look at (search engine...) [PATCH] fs: jffs2: Add setup code for
>> spi nor flash.
>>
>> Even with this patch I got some possible dead lock warnings so it might
>> be just a partial cure. BTW it's
>> a bit scary for future use. Looks like jffs2 doesn't get enough care...
> I believe the locking issues are an overlayfs regression, maybe even
> the same one as this one (which I fixed years ago):
> http://linux-fsdevel.vger.kernel.narkive.com/XRtXLDlf/patch-1-2-overlayfs-fix-a-deadlock-in-ovl-dir-read-merged
>
> I believe this is the cause of the regression:
>
> commit 49c21e1cacd74a8c83407c70ad860c994e606e25
> Author: Miklos Szeredi <mszeredi at suse.cz>
> Date:   Sat Dec 13 00:59:42 2014 +0100
>
>      ovl: check whiteout while reading directory
>      
>      Don't make a separate pass for checking whiteouts, since we can do it while
>      reading the upper directory.
>      
>      This will make it easier to handle multiple layers.
>      
>      Signed-off-by: Miklos Szeredi <mszeredi at suse.cz>
>
> It probably happens like this:
> overlayfs does a readdir, in which jffs2 takes a lock.
>  From within the readdir fill callback, it calls lookup_one_len, which
> ends up back in jffs2 and tries to take the same lock again.
> => deadlock.
This is exactly what I have seen. I have got deadlocks on readdir. 
Unfortunately I don't have any logs saved...

Wojtek
>
> - Felix
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