RAID-6 check standalone

Hi Neil,

please find attached a patch, to mdadm-3.2 base, including
a standalone versione of the raid-6 check.

This is basically a re-working (and hopefully improvement)
of the already implemented check in "restripe.c".

I splitted the check function into "collect" and "stats",
so that the second one could be easily replaced.
The API is also simplified.

The command line option are reduced, since we only level
is raid-6, but the ":offset" option is included.

The output reports the block/stripe rotation, P/Q errors
and the possible HDD (or unknown).

BTW, the patch applies also to the already patched "restripe.c",
including the last ":offset" patch (which is not yet in git).

Other item is that due to "sysfs.c" linking (see below) the
"Makefile" needed some changes, I hope this is not a problem.

Next steps (TODO list you like) would be:

1) Add the "sysfs.c" code in order to retrieve the HDDs info
from the MD device. It is already linked, together with the
whole (mdadm) universe, since it seems it cannot leave alone.
I'll need some advice or hint on how to do use it. I checked
"sysfs.c", but before I dig deep into it maybe better to
have some advice (maybe just one function call will do it).

2) Add the suspend lo/hi control. Fellow John Robinson was
suggesting to look into "Grow.c", which I did, but I guess
the same story as 1) is valid: better to have some hint on
where to look before wasting time.

3) Add a repair option (future). This should have different
levels, like "all", "disk", "stripe". That is, fix everything
(more or less like "repair"), fix only if a disk is clearly
having problems, fix each stripe which has clearly a problem
(but maybe different stripes may belong to different HDDs).

So, for the point 1) and 2) would be nice to have some more
detail on where to look what. Point 3) we will discuss later.

Thanks, please consider for inclusion,

bye,

pg

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 2 insertions, 2 deletions

diff --git a/restripe.c b/restripe.c
index a26f9e52..f579a92c 100644
--- a/restripe.c
+++ b/restripe.c
@@ -33,7 +33,7 @@
  *
  */
 
-static int geo_map(int block, unsigned long long stripe, int raid_disks,
+int geo_map(int block, unsigned long long stripe, int raid_disks,
 		   int level, int layout)
 {
 	/* On the given stripe, find which disk in the array will have
@@ -223,7 +223,7 @@ static void xor_blocks(char *target, char **sources, int disks, int size)
 	}
 }
 
-static void qsyndrome(uint8_t *p, uint8_t *q, uint8_t **sources, int disks, int size)
+void qsyndrome(uint8_t *p, uint8_t *q, uint8_t **sources, int disks, int size)
 {
 	int d, z;
 	uint8_t wq0, wp0, wd0, w10, w20;