On 10/04/2017 03:15 PM, John Stoffel wrote:

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"Jes" == Jes Sorensen [off-list ref] writes:

Jes> On 10/04/2017 02:00 PM, John Stoffel wrote:

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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

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@@ -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