Re: [RFC PATCH 0/2] wic: warn on usage of Y2038 affected file systems

["florian.bezdeka@siemens.com" <florian.bezdeka@siemens.com>]

On Thu, 2021-02-11 at 10:09 +0100, Jan Kiszka wrote:
> On 11.02.21 09:23, Henning Schild wrote:
> > Hi all,
> > 
> > i never got around to reviewing this. But did we just fork wic? These
> > patches need to go into wic and we later backport them once they are
> > accepted upstream.
> > 
> > Maybe they are already ... did not check.
> > 
> > When it comes to changing bitbake or wic, we should really not ... We
> > have forks of some files, like the wic plugins and bitbake config,
> > those are fine but should also stay very close to upstream.
> > 
> > The recently applied patch from Vijai also violates that. Since the
> > fork of the plugins was not updated with the wic bump and the repair
> > just takes a few bits of what we probably should take.
> > 
> 
> If you are referring to
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgroups.google.com%2Fd%2Fmsgid%2Fisar-users%2F20201126091750.28048-1-Vijaikumar_Kanagarajan%2540mentor.com&data=04%7C01%7Cflorian.bezdeka%40siemens.com%7Ca5e6b57fc2f34070817c08d8ce6d6dbd%7C38ae3bcd95794fd4addab42e1495d55a%7C1%7C0%7C637486316681424173%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=xERzeBGXiuxTVEC2n4CSuGmlFB9O7h07Hm9ODn33llg%3D&reserved=0:
> That one was "only" patching an isar version, though I agree that we
> should make sure to realign it with the original plugins if we are now
> imbalanced.
> 
> This one here is more critical as it changed a formerly vanilla wic
> file. That should be fixed quickly.
> 
> Florian, maybe you can propose a similar change to OE upstream? In the
> meantime, is there a chance to move the changes out of partition.py, to
> a file that is isar-specific?
> 

I guess the "RFC" tag of this series has been overlooked. It was not
intended for merging (yet). Part one (forwarding wic warnings to
bitbake) is a pure ISAR change and could be taken as is (if no further
comments come up).

Sorry for the long description of the series, but if you read closely I
already mentioned that the second part should go to OE. I sent it out
for feedback collection only.

The upstreaming to OE will take some time due to internal
clarifications. I never contributed to OE before, so some kind of
approval process has to be followed first.

At first glance there was no easy way moving the warnings from wic to
ISAR. We would have to re-parse the wic template file again and check
all the partitions afterwards. wic has all the necessary information at
hand so I guess that's way easier.


> Jan
> 
> > Henning
> > 
> > Am Thu, 11 Feb 2021 11:07:52 +0300
> > schrieb Anton Mikanovich <amikan@ilbers.de>:
> > 
> > > 01.02.2021 21:58, florian.bezdeka@siemens.com wrote:
> > > > From: Florian Bezdeka <florian.bezdeka@siemens.com>
> > > > 
> > > > Hi ISAR developers,
> > > > 
> > > > this series is the summary of a nice journey through the file system
> > > > jungle regarding Y2038 problem. It all began with a warning which is
> > > > reported by kernels >= 5.4:
> > > > 
> > > > ext4 filesystem being mounted at (mountpoint) supports timestamps
> > > > until 2038 (0x7fffffff)
> > > > 
> > > > I guess that most ISAR layers are using the Debian kernels, so that
> > > > warning was not recognized yet or at least not very often.
> > > > 
> > > > When reading this warning I was surprised. Shouldn't a modern file
> > > > system like ext4 be Y2038-safe? As it turned out it depends on the
> > > > inode size if an ext4 file system is safe or not. So why was the
> > > > inode size not sufficient in my case?
> > > > 
> > > > The inode size is chosen during file system generation and depends
> > > > on the size of the file system that is going to be created. For
> > > > details let's have a look at `man mke2fs`:
> > > > 
> > > > -T usage-type[,...]
> > > >      Specify how the filesystem is going to be used, so that mke2fs
> > > > can choose optimal filesystem parameters for that use. The usage
> > > > types that are supported are defined in the configuration file
> > > >      /etc/mke2fs.conf. The user may specify one or more usage types
> > > >      using a comma separated list.
> > > > 
> > > >      If this option is is not specified, mke2fs will pick a single
> > > >      default usage type based on the size of the filesystem to be
> > > >      created. If the filesystem size is less than 3 megabytes,
> > > > mke2fs will use the filesystem type floppy. If the filesystem size
> > > > is greater than or equal to 3 but less than 512 megabytes, mke2fs(8)
> > > >      will use the filesystem type small.
> > > > 
> > > > The relevant parts from /etc/mke2fs.conf:
> > > > [fs_types]
> > > > ...
> > > >          small = {
> > > >                  blocksize = 1024
> > > >                  inode_size = 128
> > > >                  inode_ratio = 4096
> > > >          }
> > > > ...
> > > > 
> > > > So whenever you create an ext4 file system with less than 512MB in
> > > > size you will end up with 128 byte inodes and your file system is
> > > > not Y2038-safe.
> > > > 
> > > > The ISAR part:
> > > > ext4 may often be used in combination with the expand-on-first-boot
> > > > recipe / feature. So whenever creating a small partition (e.g.
> > > > inside a wic file) and extending it later may result in a Y2038
> > > > affected ext4 file system.
> > > > 
> > > > That is exactly what happened to me and I would like to make sure
> > > > that all other ISAR users are aware of this situation.
> > > > 
> > > > Valid workarounds found so far:
> > > >   - Tell wic that an partition will grow:
> > > >     Add `--mkfs-extraopts "-T ext4"` to your wic partition
> > > > definition
> > > >   - Set the inode size to 256 (for small ext4 partitions)
> > > >     Add `--mkfs-extraopts "-I 256"` to your wic partition definition
> > > > 
> > > > The upstream part:
> > > > None of the following patches has been sent to any upstream (OE)
> > > > mailing lists yet but hopefully that will happen soon. So far: Any
> > > > comments welcome!
> > > > 
> > > > Best regards,
> > > > Florian
> > > > 
> > > > Florian Bezdeka (2):
> > > >    wic-img: Forward warnings from wic to bitbake
> > > >    wic: Warn if an ext filesystem affected by the Y2038 problem is
> > > > used
> > > > 
> > > >   meta/classes/wic-img.bbclass | 20 ++++++++++++++-----
> > > >   scripts/lib/wic/partition.py | 38
> > > > ++++++++++++++++++++++++++++++++++++ 2 files changed, 53
> > > > insertions(+), 5 deletions(-) 
> > > Applied to next, thanks.
> > > 
> > 
> 
>