Re: [PATCH v4 3/4] btrfs: add device major-minor info in the struct btrfs_device

[Goffredo Baroncelli <kreijack@inwind.it>]

On 12/01/2022 04.17, Anand Jain wrote:
> 
> 
[...]
>>
>> Ok, I think that this case (where devt!=0 and bdev==NULL) should be inserted as comment in the structure before the devt field.
> 
> I will add but, did you find any pitfall for breaking such a case?
> Or are you submitting any patch based on this rule?

In a patch that I sent few days ago, I exported the major/minor
in <UUID>/devinfo/<devid>/major-minor sysfs property.
In order to do that, I taken the values from btrfs_device->bdev->bd_dev,
checking that bdev is not NULL.
So I didn't understood why we need to add copy of devt also
is the btrfs_device structure, because it is easy to taken the bdev one.

You answer was "we need that, because sometime bdev is NULL even
if a reasonable devt value exist", which is a valid reason.
So I suggest to add this info in the header so even the "next" developer
with a no so deep knowledge of the btrfs device life-cycle will be
aware of this case.

BR
G.Baroncelli
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