APPLIED[K]: [SRU][J/K/J:hwe-5.17[PATCH 0/2] refactoring of overlayfs fix to properly support shiftfs

[Andrea Righi]

On Fri, Aug 05, 2022 at 08:32:09AM +0200, Andrea Righi wrote:
> [Impact]
> 
> Starting with 5.13 we've incorrectly dropped the following sauce patch:
> 
>   UBUNTU: SAUCE: overlayfs: fix incorrect mnt_id of files opened from map_files
> 
> This patch is required to use overlayfs on top of shiftfs and without
> this patch we may break containers that rely on shiftfs (using zfs/ceph
> as storage pool w/ shiftfs enabled).
> 
> However, we made this patch dependent on AUFS, starting with Jammy we're
> not enabling AUFS anymore, so this fix becomes a no-op.
> 
> So we need to re-introduce this fix with a bit of refactoring to not
> depend on AUFS.
> 
> [Test case]
> 
> The following script can be used to trigger the issue:
> 
>   #!/bin/bash
> 
>   cat > test.py << EOF
>   import sys
> 
>   f = open("/proc/self/maps")
> 
>   for l in f.readlines():
>     if "python" not in l:
>       continue
>     print(l)
>     s = l.split()
>     start, end = s[0].split("-")
>     fname = s[-1]
>     print(start, end, fname)
>     break
>   else:
>     sys.exit(1)
> 
>   test_file1 = open(fname)
>   test_file2 = open("/proc/self/map_files/%s-%s" % (start, end))
> 
>   fdinfo1 = open("/proc/self/fdinfo/%d" % test_file1.fileno()).read()
>   fdinfo2 = open("/proc/self/fdinfo/%d" % test_file2.fileno()).read()
> 
>   if fdinfo1 != fdinfo2:
>     print("FAIL")
>     print(test_file1)
>     print(fdinfo1)
>     print(test_file2)
>     print(fdinfo2)
>     sys.exit(1)
>   print("PASS")
>   EOF
>   sudo docker run -it --privileged --rm -v `pwd`:/mnt python python /mnt/test.py
> 
> [Fix]
> 
> Import the right pieces from AUFS to properly support the fix and get
> rid of the AUFS dependency across all our kernels and re-apply the
> overlayfs fix without the AUFS dependency.
> 
> [Regression potential]
> 
> This patch is touching overlayfs, so we may see potential regressions in
> overlayfs, especially when containers are used.
> 
> [Additional notes]
> 
> We need different patches for Jammy and Kinetic, because Kinetic is
> missing AUFS completely, so we need to import the chunk of code from
> AUFS that we were relying to, in order to properly apply the overlayfs
> fix.
> 
> Moreover, J/hwe-5.17 also needs a fix, because this kernel is now
> "detached" (it doesn't have a parent anymore), so it's following its own
> development workflow, like a master kernel.

Applied to kinetic/linux.

-Andrea