Re: crash zfs_clone_range()

On 11/14/23, Alexander Motin <mav@freebsd.org> wrote:
> On 14.11.2023 12:44, Alexander Motin wrote:
>> On 14.11.2023 12:39, Mateusz Guzik wrote:
>>> One of the vnodes is probably not zfs, I suspect this will do it
>>> (untested):
>>>
>>> diff --git a/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c
>>> b/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c
>>> index 107cd69c756c..e799a7091b8e 100644
>>> --- a/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c
>>> +++ b/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c
>>> @@ -6270,6 +6270,11 @@ zfs_freebsd_copy_file_range(struct
>>> vop_copy_file_range_args *ap)
>>>                          goto bad_write_fallback;
>>>                  }
>>>          }
>>> +
>>> +       if (invp->v_mount->mnt_vfc != outvp->v_mount->mnt_vfc) {
>>> +               goto bad_write_fallback;
>>> +       }
>>> +
>>>          if (invp == outvp) {
>>>                  if (vn_lock(outvp, LK_EXCLUSIVE) != 0) {
>>>                          goto bad_write_fallback;
>>>
>>
>> vn_copy_file_range() verifies for that:
>>
>>          /*
>>           * If the two vnodes are for the same file system type, call
>>           * VOP_COPY_FILE_RANGE(), otherwise call
>> vn_generic_copy_file_range()
>>           * which can handle copies across multiple file system types.
>>           */
>>          *lenp = len;
>>          if (inmp == outmp || strcmp(inmp->mnt_vfc->vfc_name,
>>              outmp->mnt_vfc->vfc_name) == 0)
>>                  error = VOP_COPY_FILE_RANGE(invp, inoffp, outvp,
>> outoffp,
>>                      lenp, flags, incred, outcred, fsize_td);
>>          else
>>                  error = vn_generic_copy_file_range(invp, inoffp, outvp,
>>                      outoffp, lenp, flags, incred, outcred, fsize_td);
>
> Thinking again, what happen if there are two nullfs mounts on top of two
> different file systems, one of which is indeed not ZFS?  Do we need to
> add those checks to all ZFS, NFS and FUSE, implementing
> VOP_COPY_FILE_RANGE, or it is responsibility of nullfs or VFS?
>

I already advocated for not trying to guess for filesystems what they
can or cannot handle internally.

That is to say vn_copy_file_range should call VOP_COPY_FILE_RANGE,
that can try to figure out what to do and if it got nothing punt to a
fallback. This already happens for some of the cases.

-- 
Mateusz Guzik <mjguzik gmail.com>