Re: report a bug that panic when grow size for external bitmap

[NeilBrown <neilb@suse.com>]

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On Thu, Aug 31 2017, Zhilong Liu wrote:

> On 08/31/2017 08:27 AM, NeilBrown wrote:
>> On Wed, Aug 30 2017, Zhilong Liu wrote:
>>
>>> On 08/29/2017 06:47 PM, NeilBrown wrote:
>>>> Thanks.  I see what I missed. Please try this patch instead.
>>> Hi, Neil;
>>>       I have tested the following patch, I still got the call-trace after
>>> I built with it.
>>> If you need other infos, I would append.
>>
>> Thanks for testing.
>> I looked more completely and I think it is easiest just to disable the
>> functionality rather than try to fix it.
>> Resizing the file in the kernel is extra complexity that I don't
>> want to get in to.
>> We could adjust the bitmap chunk size so that the file doesn't
>> need to grow, but it started getting more complicated than I really
>> wanted to deal with.
>> If there is anyone actually using file-backed bitmaps who wants to
>> be able to resize the array without removing the bitmap first, then
>> we can look at the problem again.  For now I've sent a patch which
>> just returns an error instead of crashing when someone tries to resize
>> an array with a file-backed bitmap.
>
> Hi, Neil;
>      Shall update the "SIZE CHANGES" under "GROW MODE" of man-page for
> resize like following after kernel patch merged?

Good idea, but it isn't just "--grow --size".  It is anything that
changes the size of the array, which includes changing the number of
devices in a RAID5 etc.  So a more general statement would be better.

NeilBrown

>
> Thanks,
> -Zhilong
>
> diff --git a/mdadm.8.in b/mdadm.8.in
> index e0747fb..f0fd1fc 100644
> --- a/mdadm.8.in
> +++ b/mdadm.8.in
> @@ -2758,6 +2758,11 @@ Also the size of an array cannot be changed while 
> it has an active
>   bitmap.  If an array has a bitmap, it must be removed before the size
>   can be changed. Once the change is complete a new bitmap can be created.
>
> +.PP
> +Note:
> +.B "--grow --size"
> +is not yet supported for external file bitmap.
> +
>   .SS RAID\-DEVICES CHANGES
>
>   A RAID1 array can work with any number of devices from 1 upwards
>
>> Thanks,
>> NeilBrown

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