Re: PROBLEM: Reiser4 hard lockup

[David Niklas]

I'll reply to both of you in this email.

On Sun, 25 Oct 2020 02:04:22 -0700 (PDT)
Metztli Information Technology <jose.r.r@xxxxxxxxxxx> wrote:
> Niltze, David-
> 
> A few observations are in order below:
> 
> On Sat, Oct 24, 2020 at 1:39 PM David Niklas <Hgntkwis@xxxxxxxxxxx>
> wrote:
> >
> > Hello,
> >
<snip>
> reiser4progs 1.1.x Software Framework Release Number (SFRN) 4.0.1 file
> system utilities should not be used to check/fix media formatted 'a
> priori' in SFRN 4.0.2 and vice-versa.

Honestly, this is the first time I've heard about a Linux FS having
versioning other than a major one (NTFS IIRC is infamous for it's
incompatibilities).

<snip>

> Conclusion: I suggest you read up on the published reiser4
> documentation and build *both* your kernel and reiser4progs utilities
> conforming to the more recent stable SFRN 4.0.2.

I religiously read the reiser4 documentation prior to changing my FS. No
where do I recall seeing, on the wiki, or in the man pages, that there
was a need to use a newer reiser4 progs.
Ok, here it is:
https://reiser4.wiki.kernel.org/index.php/Reiser4_development_model
I'm not normally going to read a page that looks like it's for developers
as an end user which is why I didn't initially read it.

> Prior to build reiser4progs 1.2.1 SFRN 4.0.2:
> libaal-1.0.7.tar.gz
> < https://sourceforge.net/projects/reiser4/files/reiser4-utils/ >
> 
> then build reiser4progs-1.2.1.tar.gz SFRN 4.0.2
> <
> https://sourceforge.net/projects/reiser4/files/reiser4-utils/reiser4progs/
> >
> 
> as any reiser4 patches for kernel 4.14 and higher conform to SFRN 4.0.2:
> https://sourceforge.net/projects/reiser4/files/reiser4-for-linux-5.x/
> 
> citing, for the third time, reference email documenting the change,
> i.e. '2017-11-26 23:01:53 reiser4 SFRN 4.0.2 is not your father's
> reiser4 SFRN 4.0.1' <
> https://marc.info/?l=reiserfs-devel&m=151173731709826&w=2 >
> 
> If you are going to use reiser4 kernel patches for linux 4.15.xy -
> 5.4.5 range, please make sure to *also* apply: [PATCH] reiser4: prevent
> system lockups: <
> https://marc.info/?l=reiserfs-devel&m=158086248927420&w=2 >
<snip>

I was using 5.7.13 at the time. Should the crashes still be happening
because this patch is missing? It seems odd you'd mention it knowing
which kernel version I was using.


On Sun, 25 Oct 2020 13:50:15 +0100
Edward Shishkin <edward.shishkin@xxxxxxxxx> wrote:
> On 10/24/2020 10:36 PM, David Niklas wrote:
> > Hello,
> >   
> 
> Hi David,
> 
> Thanks for the comprehensive report, which is definitely useful!
> Below you can find some hints and comments.
> 

(:

<snip>
> 
> It's a pity..
> To be honest, I received complaints that reiser4 doesn't make
> a friendship with torrents long time ago. Unfortunately, I am in Europe,
> where it is impossible to use torrents that simply, without conflicts
> with local legislation. Respectively, I am not able to reproduce it,
> and the problem is still unfixed..
> 
I might try to reproduce this later and log the actual write patterns so
you can reproduce these crashes. Obviously, I'll have to learn how to
first.

<snip>
> reiser4 mount option "dont_load_bitmap" is your friend.

I knew about that, but I'm uncertain if it would change how reiser4 works
and then it will not cause the crash.

> > I had also to manually chew through all the kernel .o files to find
> > where the kernel broke at (also attached).
> > 
> > The command I used to create the reiser4 FS was:
> > mkfs.reiser4 -o
> > create=reg40,fibration=ext_3_fibre,hash=r5_hash,key=key_large,node=node40,compress=lzo1,compressMode=conv /dev/md7p1
> > I wanted to use reg40 as opposed to ccreg40 because I wanted an
> > unencrypted partition.  
> 
> 
> You got confused. Reiser4 doesn't support encryption without special
> patches (which are not public). With "create=reg40" you get a "classic"
> setup without compression.
> 
> There is a "getting started" page, which provides some recommendations
> on reiser4 mkfs and mount options:
> https://reiser4.wiki.kernel.org/index.php/Reiser4_Howto

Ah, I read that page 4 times but thought it out of date because the
plugin description said something else.

> > Likewise, I changed the fibration to ext_3_fibre
> > from ext_1_fibre. Other then that, everything is set to it's defaults.
> > Interestingly, if I try to set the key to short and change the mode to
> > tea (a time compute trade off AFAIK), I crashes mkfs.reiser4.
> > I need to report this to the developers.  
> 
> Short keys is an exotic option (are you restricted in disk space?).

Quite the contrary, I wanted an excuse to try using tea. IDK what the key
lengths are (I've been really curious about that), but I decided to try
using tea and short hashes as a fun exercise as a time/compute trade off.

> But that crash needs to be fixed, of course. I'll create a ticket.

Nice!
 
> > When trying to remount the FS after this crash I got an error from
> > fsck that I needed to rebuild the super block. Considering that all
> > transactions are atomic, this was quite a surprise to me.
> > This failed because the format version was somehow greater than my
> > tools version.  
> 
> 
> Absolutely.
> 
> SFRN (Software Framework Release Number) of your tools is 4.0.1.
> SFRN of your reiser4 module is 4.0.2.
> Right after formatting your partition had format 4.0.1.
> After mounting to the kernel of greater SFRN, it was automatically
> upgraded to 4.0.2, so you are not able to check that partition with
> fsck of smaller SFRN anymore. All you needed was to upgrade your
> reiser4progs.
>
> More about compatibility is here:
> https://reiser4.wiki.kernel.org/index.php/Reiser4_development_model

Ah! I wondered how I could create an FS that had a larger version than my
tools.


> > One thing that was quite interesting about this is that the Linux
> > kernel said I needed to upgrade my disk format of reiser 4.
> > Sep 19 04:21:16 Phenom-II-x6 kernel: [   37.113970][ T2122]
> > Loading Reiser4 (format release: 4.0.2) See www.namesys.com for a
> > description of Reiser4.
> > Sep 19 04:21:16 Phenom-II-x6 kernel: [   37.132956][ T2121]
> > reiser4: md7p1: found disk format 4.0.2.
> > Sep 19 04:21:16 Phenom-II-x6 kernel: [   37.133792][ T2121]
> > reiser4: md7p1: use 'fsck.reiser4 --fix' to complete disk format
> > upgrade. 
> 
> 
> It is expected, since you mounted partition 4.0.1 by reiser4 module
> 4.0.2. No hurry to complete disk format upgrade. It is needed by fsck
> only.

So the upgrade was only partial?

> > IDR If I tried to issue the above recommended command.
> > 
> > 
> > Overall, after over a decade of development, I had hoped that reiser4
> > would prove to be a fast, space efficient, and stable FS.  
> 
> 
> So, as I understand, the only problem is stability?
> What can I say... We are not enterprise. We are like the upstream
> vanilla kernel, which can always be corrupted in some configuration
> under a specific workload, despite 30 years(!) of development history.
> Motivation to fix bugs is driven mostly by users and their bug reports
> (similar to ones that you have provided)..

I know. I know. It's just after reading several months of emails from the
LKML where Hans goes on and on about how wonderfully stable it is and
every bug is quickly quashed, I thought it would be as stable as a
boulder.
And using ext3 as a baseline didn't help either. (:

<snip>
> Thanks again for the report.
> Once we fix the problem with torrents, we'll let you know..
> 
> Edward.


Thanks,
David