Re: [PATCH] (Re: Questions regarding startup of imsm container)

[Dan Williams <dan.j.williams@intel.com>]

On Tue, Mar 23, 2010 at 5:57 PM, Neil Brown <neilb@suse.de> wrote:
> On Tue, 23 Mar 2010 09:04:19 +0100
> Luca Berra <bluca@comedia.it> wrote:
>
>> On Mon, Mar 22, 2010 at 09:56:01PM -0600, Randy Terbush wrote:
>> >Having a go at building a raid5 array using the new imsm support and
>> >having good luck keeping drives in the array, etc. Nice work. I have a
>> >few questions though as I am having some trouble figuring out how to
>> >properly start this container.
>> >
>> ># mdadm --version
>> >mdadm - v3.1.2 - 10th March 2010
>> >
>> ># mdadm -Es
>> >ARRAY metadata=imsm UUID=30223250:76fd248b:50280919:0836b7f0
>> >ARRAY /dev/md/Volume0 container=30223250:76fd248b:50280919:0836b7f0
>> >member=0 UUID=8a4ae452:da1e7832:70ecf895:eb58229c
>> >
>> ># ls -l /dev/md/
>> >total 0
>> >lrwxrwxrwx 1 root root 6 Mar 22 20:54 0 -> ../md0
>> >lrwxrwxrwx 1 root root 8 Mar 22 20:54 127 -> ../md127
>> >lrwxrwxrwx 1 root root 8 Mar 22 20:54 Volume0_0 -> ../md127
>> >
>> >As you can see, the name for the link in /dev/md does not agree with
>> >the name that the Examine is coming up with.
>> please read mdadm.conf manpage, under the section "HOMEHOST"
>>
>> >Is it better to just forgo the ARRAY statements and go with an AUTO +imsm?
>> >
>> >And last, does the concept of a write-intent bitmap make sense on an
>> >imsm container? If so, I get a segv if trying to run mdadm /dev/mdX
>> >-Gb internal on either device.
>>
>> i don't believe it makes sense at all, surely imsm do not support an
>> internal bitmap (no provisioning for it in the metadata)
>>
>> The attached patch completely disables bitmap support for arrays with
>> externally managed metadata.
>
> Thanks for the patch.  However I would prefer to disable bitmap support for
> those metadata formats which report that they don't support it.
> Thus the following patch.
>
> Thanks,
> NeilBrown
>
>
> +               if (!st->ss->add_internal_bitmap) {
[..]
> +               if (st->ss->add_internal_bitmap == NULL) {
[..]
> +               } else if (!st->ss->locate_bitmap) {

The smallest of nits, or maybe just a clarification.  I believe you
have said in the past that you prefer the readability of
positive-logic if statements where possible.

--
Dan
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