On 2019/08/16 16:57, Anand Jain wrote:
>
>
> On 8/16/19 10:23 PM, Damien Le Moal wrote:
>> On 2019/08/15 22:46, Anand Jain wrote:
>>> On 8/8/19 5:30 PM, Naohiro Aota wrote:
>>>> HMZONED mode cannot be used together with the RAID5/6 profile for now.
>>>> Introduce the function btrfs_check_hmzoned_mode() to check this. This
>>>> function will also check if HMZONED flag is enabled on the file system and
>>>> if the file system consists of zoned devices with equal zone size.
>>>>
>>>> Additionally, as updates to the space cache are in-place, the space cache
>>>> cannot be located over sequential zones and there is no guarantees that the
>>>> device will have enough conventional zones to store this cache. Resolve
>>>> this problem by disabling completely the space cache. This does not
>>>> introduces any problems with sequential block groups: all the free space is
>>>> located after the allocation pointer and no free space before the pointer.
>>>> There is no need to have such cache.
>>>>
>>>> For the same reason, NODATACOW is also disabled.
>>>>
>>>> Also INODE_MAP_CACHE is also disabled to avoid preallocation in the
>>>> INODE_MAP_CACHE inode.
>>>
>>> A list of incompatibility features with zoned devices. This need better
>>> documentation, may be a table and its reason is better.
>>
>> Are you referring to the format of the commit message itself ? Or would you like
>> to see a documentation added to Documentation/filesystems/btrfs.txt ?
>
> Documenting in the commit change log is fine. But it can be better
> documented in a listed format as it looks like we have a list of
> features which will be incompatible with zoned devices.
OK. We can update btrfs.txt doc file.
>
> more below..
[...]>>>> + if (!hmzoned_devices && incompat_hmzoned) {
>>>> + /* No zoned block device found on HMZONED FS */
>>>> + btrfs_err(fs_info, "HMZONED enabled file system should have zoned devices");
>>>> + ret = -EINVAL;
>>>> + goto out;
>>>
>>>
>>> When does the HMZONED gets enabled? I presume during mkfs. Where are
>>> the related btrfs-progs patches? Searching for the related btrfs-progs
>>> patches doesn't show up anything in the ML. Looks like I am missing
>>> something, nor the cover letter said anything about the progs part.
>
>
> Any idea about this comment above?
Yep, the feature is set at format time if some of the devices in the volume are
zoned. The btrfs-progs changes to handle that are ready too.
Naohiro, please re-post btrfs-progs too !
>
> Thanks, Anand
--
Damien Le Moal
Western Digital Research
