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, 262 insertions, 0 deletions

diff --git a/raid6check.c b/raid6check.c
new file mode 100644
index 0000000..97e3f1c
--- /dev/null
+++ b/raid6check.c
@@ -0,0 +1,262 @@
+/*
+ * raid6check - extended consistency check for RAID-6
+ *
+ * Copyright (C) 2011 Piergiorgio Sartor
+ *
+ *
+ *    This program is free software; you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation; either version 2 of the License, or
+ *    (at your option) any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program; if not, write to the Free Software
+ *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *    Author: Piergiorgio Sartor
+ *    Based on "restripe.c" from "mdadm" codebase
+ */
+
+#include "mdadm.h"
+#include <stdint.h>
+
+int geo_map(int block, unsigned long long stripe, int raid_disks,
+	    int level, int layout);
+void qsyndrome(uint8_t *p, uint8_t *q, uint8_t **sources, int disks, int size);
+void make_tables(void);
+
+/* Collect per stripe consistency information */
+void raid6_collect(int chunk_size, uint8_t *p, uint8_t *q,
+		   char *chunkP, char *chunkQ, int *results)
+{
+	int i;
+	int data_id;
+	uint8_t Px, Qx;
+	extern uint8_t raid6_gflog[];
+
+	for(i = 0; i < chunk_size; i++) {
+		Px = (uint8_t)chunkP[i] ^ (uint8_t)p[i];
+		Qx = (uint8_t)chunkQ[i] ^ (uint8_t)q[i];
+
+		if((Px != 0) && (Qx == 0))
+			results[i] = -1;
+
+		if((Px == 0) && (Qx != 0))
+			results[i] = -2;
+
+		if((Px != 0) && (Qx != 0)) {
+			data_id = (raid6_gflog[Qx] - raid6_gflog[Px]);
+			if(data_id < 0) data_id += 255;
+			results[i] = data_id;
+		}
+
+		if((Px == 0) && (Qx == 0))
+			results[i] = -255;
+	}
+}
+
+/* Try to find out if a specific disk has problems */
+int raid6_stats(int *results, int raid_disks, int chunk_size)
+{
+	int i;
+	int curr_broken_disk = -255;
+	int prev_broken_disk = -255;
+	int broken_status = 0;
+
+	for(i = 0; i < chunk_size; i++) {
+
+		if(results[i] != -255)
+			curr_broken_disk = results[i];
+
+		if(curr_broken_disk >= raid_disks)
+			broken_status = 2;
+
+		switch(broken_status) {
+		case 0:
+			if(curr_broken_disk != -255) {
+				prev_broken_disk = curr_broken_disk;
+				broken_status = 1;
+			}
+			break;
+
+		case 1:
+			if(curr_broken_disk != prev_broken_disk)
+				broken_status = 2;
+			break;
+
+		case 2:
+		default:
+			curr_broken_disk = prev_broken_disk = -65535;
+			break;
+		}
+	}
+
+	return curr_broken_disk;
+}
+
+int check_stripes(int *source, unsigned long long *offsets,
+		  int raid_disks, int chunk_size, int level, int layout,
+		  unsigned long long start, unsigned long long length, char *name[])
+{
+	/* read the data and p and q blocks, and check we got them right */
+	char *stripe_buf = malloc(raid_disks * chunk_size);
+	char **stripes = malloc(raid_disks * sizeof(char*));
+	char **blocks = malloc(raid_disks * sizeof(char*));
+	uint8_t *p = malloc(chunk_size);
+	uint8_t *q = malloc(chunk_size);
+	int *results = malloc(chunk_size * sizeof(int));
+
+	int i;
+	int diskP, diskQ;
+	int data_disks = raid_disks - 2;
+
+	extern int tables_ready;
+
+	if (!tables_ready)
+		make_tables();
+
+	for ( i = 0 ; i < raid_disks ; i++)
+		stripes[i] = stripe_buf + i * chunk_size;
+
+	while (length > 0) {
+		int disk;
+
+		for (i = 0 ; i < raid_disks ; i++) {
+			lseek64(source[i], offsets[i]+start, 0);
+			read(source[i], stripes[i], chunk_size);
+		}
+		for (i = 0 ; i < data_disks ; i++) {
+			int disk = geo_map(i, start/chunk_size, raid_disks,
+					   level, layout);
+			blocks[i] = stripes[disk];
+			printf("%d->%d\n", i, disk);
+		}
+
+		qsyndrome(p, q, (uint8_t**)blocks, data_disks, chunk_size);
+		diskP = geo_map(-1, start/chunk_size, raid_disks,
+				level, layout);
+		if (memcmp(p, stripes[diskP], chunk_size) != 0) {
+			printf("P(%d) wrong at %llu\n", diskP,
+			       start / chunk_size);
+		}
+		diskQ = geo_map(-2, start/chunk_size, raid_disks,
+				level, layout);
+		if (memcmp(q, stripes[diskQ], chunk_size) != 0) {
+			printf("Q(%d) wrong at %llu\n", diskQ,
+			       start / chunk_size);
+		}
+		raid6_collect(chunk_size, p, q,
+			      stripes[diskP], stripes[diskQ], results);
+		disk = raid6_stats(results, raid_disks, chunk_size);
+
+		if(disk >= -2) {
+			disk = geo_map(disk, start/chunk_size, raid_disks,
+				       level, layout);
+		}
+		if(disk >= 0) {
+			printf("Possible failed disk: %d --> %s\n", disk, name[disk]);
+		}
+		if(disk == -65535) {
+			printf("Failure detected, but disk unknown\n");
+		}
+
+		length -= chunk_size;
+		start += chunk_size;
+	}
+
+	free(stripe_buf);
+	free(stripes);
+	free(blocks);
+	free(p);
+	free(q);
+	free(results);
+
+	return 0;
+}
+
+unsigned long long getnum(char *str, char **err)
+{
+	char *e;
+	unsigned long long rv = strtoull(str, &e, 10);
+	if (e==str || *e) {
+		*err = str;
+		return 0;
+	}
+	return rv;
+}
+
+int main(int argc, char *argv[])
+{
+	/* raid_disks chunk_size layout start length devices...
+	 */
+	int *fds;
+	char *buf;
+	unsigned long long *offsets;
+	int raid_disks, chunk_size, layout;
+	int level = 6;
+	unsigned long long start, length;
+	int i;
+
+	char *err = NULL;
+	if (argc < 8) {
+		fprintf(stderr, "Usage: raid6check raid_disks"
+			" chunk_size layout start length devices...\n");
+		exit(1);
+	}
+
+	raid_disks = getnum(argv[1], &err);
+	chunk_size = getnum(argv[2], &err);
+	layout = getnum(argv[3], &err);
+	start = getnum(argv[4], &err);
+	length = getnum(argv[5], &err);
+	if (err) {
+		fprintf(stderr, "test_stripe: Bad number: %s\n", err);
+		exit(2);
+	}
+	if (argc != raid_disks + 6) {
+		fprintf(stderr, "test_stripe: wrong number of devices: want %d found %d\n",
+			raid_disks, argc-6);
+		exit(2);
+	}
+	fds = malloc(raid_disks * sizeof(*fds));
+	offsets = malloc(raid_disks * sizeof(*offsets));
+	memset(offsets, 0, raid_disks * sizeof(*offsets));
+
+	for (i=0; i<raid_disks; i++) {
+		char *p;
+		p = strchr(argv[6+i], ':');
+
+		if(p != NULL) {
+			*p++ = '\0';
+			offsets[i] = atoll(p) * 512;
+		}
+		fds[i] = open(argv[6+i], O_RDWR);
+		if (fds[i] < 0) {
+			perror(argv[6+i]);
+			fprintf(stderr,"test_stripe: cannot open %s.\n", argv[6+i]);
+			exit(3);
+		}
+	}
+
+	buf = malloc(raid_disks * chunk_size);
+
+	int rv = check_stripes(fds, offsets,
+			       raid_disks, chunk_size, level, layout,
+			       start, length, &argv[6]);
+	if (rv != 0) {
+		fprintf(stderr,
+			"test_stripe: test_stripes returned %d\n", rv);
+		exit(1);
+	}
+
+	free(fds);
+	free(offsets);
+	free(buf);
+
+	exit(0);
+}