Re: mdadm: Patch to restrict --size when shrinking unless forced

[Jes Sorensen <jes.sorensen@gmail.com>]

On 10/04/2017 03:15 PM, John Stoffel wrote:
>>>>>> "Jes" == Jes Sorensen <jes.sorensen@gmail.com> writes:
> 
> Jes> On 10/04/2017 02:00 PM, John Stoffel wrote:
>>>
>>> Since Eli had such a horrible experience where he shrunk the
>>> individual component raid device size, instead of growing the overall
>>> raid by adding a device, I came up with this hacky patch to warn you
>>> when you are about to shoot yourself in the foot.
>>>
>>> The idea is it will warn you and exit unless you pass in the --force
>>> (or -f) switch when using the command.  For example, on a set of loop
>>> devices:
>>>
>>> # cat /proc/mdstat
>>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5]
>>> [raid4] [multipath] [faulty]
>>> md99 : active raid6 loop4p1[4] loop3p1[3] loop2p1[2] loop1p1[1]
>>> loop0p1[0]
>>> 606720 blocks super 1.2 level 6, 512k chunk, algorithm 2 [5/5]
>>> [UUUUU]
>>>
>>> # ./mdadm --grow /dev/md99 --size 128
>>> mdadm: Cannot set device size smaller than current component_size of /dev/md99 array.  Use -f to force change.
>>>
>>> # ./mdadm --grow /dev/md99 --size 128 -f
>>> mdadm: component size of /dev/md99 has been set to 0K
>>>
>>>
>>> I suspect I could do a better job of showing the original component
>>> size, so that you have a chance of recovering even then.
>>>
>>> But the patch:
> 
> Jes> Before looking at the actual code, some cosmetics
> 
> Sure, I'll re-spin the patch,  I have my emacs setup to use 4 spaces
> for indentation, not 8 space tabs.

mdadm follows Linux kernel rules, so (setq c-basic-offset 8) in .emacs

>>> @@ -1617,7 +1617,7 @@ int main(int argc, char *argv[])
>>> else if (s.size > 0 || s.raiddisks || s.layout_str ||
>>> s.chunk != 0 || s.level != UnSet ||
>>> data_offset != INVALID_SECTORS) {
>>> -			rv = Grow_reshape(devlist->devname, mdfd,
>>> +		    rv = Grow_reshape(devlist->devname, mdfd, c.force,
> 
> Jes> Yikes!
> 
> Can you explain please?  I added in the c.force since that's the value
> set by the -f (--force) flag when you call mdadm from the command
> line.

The broken indentation

Jes