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

[Jan Kiszka <jan.kiszka@siemens.com>]

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://groups.google.com/d/msgid/isar-users/20201126091750.28048-1-Vijaikumar_Kanagarajan%40mentor.com:
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?

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.
>>
> 


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