Repair mode for raid6

In repair mode, raid6check will rewrite one single stripe
by regenerating the data (or parity) of two raid devices that
are specified via the command line.
If you need to rewrite just one slot, pick any other slot
at random.

Note that the repair option will change data on the disks
directly, so both the md layer above as well as any layers
above md (such as filesystems) may be accessing the stripe
data from cached buffers. Either instruct the kernels
to drop the caches or reassemble the raid after repair.

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

1 files changed, 128 insertions, 5 deletions

diff --git a/raid6check.c b/raid6check.c
index be7a449e..aba8160f 100644
--- a/raid6check.c
+++ b/raid6check.c
@@ -31,6 +31,12 @@ 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);
+void ensure_zero_has_size(int chunk_size);
+void raid6_datap_recov(int disks, size_t bytes, int faila, uint8_t **ptrs);
+void raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
+		       uint8_t **ptrs);
+void xor_blocks(char *target, char **sources, int disks, int size);
+
 
 /* Collect per stripe consistency information */
 void raid6_collect(int chunk_size, uint8_t *p, uint8_t *q,
@@ -103,7 +109,8 @@ int raid6_stats(int *results, int raid_disks, int chunk_size)
 
 int check_stripes(struct mdinfo *info, 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[])
+		  unsigned long long start, unsigned long long length, char *name[],
+		  int repair, int failed_disk1, int failed_disk2)
 {
 	/* read the data and p and q blocks, and check we got them right */
 	char *stripe_buf = xmalloc(raid_disks * chunk_size);
@@ -170,10 +177,13 @@ int check_stripes(struct mdinfo *info, int *source, unsigned long long *offsets,
 
 		qsyndrome(p, q, (uint8_t**)blocks, data_disks, chunk_size);
 		diskP = geo_map(-1, start, raid_disks, level, layout);
+		diskQ = geo_map(-2, start, raid_disks, level, layout);
+		blocks[data_disks] = stripes[diskP];
+		blocks[data_disks+1] = stripes[diskQ];
+
 		if (memcmp(p, stripes[diskP], chunk_size) != 0) {
 			printf("P(%d) wrong at %llu\n", diskP, start);
 		}
-		diskQ = geo_map(-2, start, raid_disks, level, layout);
 		if (memcmp(q, stripes[diskQ], chunk_size) != 0) {
 			printf("Q(%d) wrong at %llu\n", diskQ, start);
 		}
@@ -190,6 +200,86 @@ int check_stripes(struct mdinfo *info, int *source, unsigned long long *offsets,
 		if(disk == -65535) {
 			printf("Error detected at %llu: disk slot unknown\n", start);
 		}
+		if(repair == 1) {
+			printf("Repairing stripe %llu\n", start);
+			printf("Assuming slots %d (%s) and %d (%s) are incorrect\n",
+			       failed_disk1, name[failed_disk1],
+			       failed_disk2, name[failed_disk2]);
+
+			if (failed_disk1 == diskQ || failed_disk2 == diskQ) {
+				char *all_but_failed_blocks[data_disks];
+				int failed_data;
+				int failed_block_index;
+
+				if (failed_disk1 == diskQ)
+					failed_data = failed_disk2;
+				else
+					failed_data = failed_disk1;
+				printf("Repairing D/P(%d) and Q\n", failed_data);
+				failed_block_index = geo_map(
+					failed_data, start, raid_disks,
+					level, layout);
+				for (i=0; i < data_disks; i++)
+					if (failed_block_index == i)
+						all_but_failed_blocks[i] = stripes[diskP];
+					else
+						all_but_failed_blocks[i] = blocks[i];
+				xor_blocks(stripes[failed_data],
+					all_but_failed_blocks, data_disks, chunk_size);
+				qsyndrome(p, (uint8_t*)stripes[diskQ], (uint8_t**)blocks, data_disks, chunk_size);
+			} else {
+				ensure_zero_has_size(chunk_size);
+				if (failed_disk1 == diskP || failed_disk2 == diskP) {
+					int failed_data, failed_block_index;
+					if (failed_disk1 == diskP)
+						failed_data = failed_disk2;
+					else
+						failed_data = failed_disk1;
+					failed_block_index = geo_map(failed_data, start, raid_disks, level, layout);
+					printf("Repairing D(%d) and P\n", failed_data);
+					raid6_datap_recov(raid_disks, chunk_size, failed_block_index, (uint8_t**)blocks);
+				} else {
+					printf("Repairing D and D\n");
+					int failed_block_index1 = geo_map(failed_disk1, start, raid_disks, level, layout);
+					int failed_block_index2 = geo_map(failed_disk2, start, raid_disks, level, layout);
+					if (failed_block_index1 > failed_block_index2) {
+						int t = failed_block_index1;
+						failed_block_index1 = failed_block_index2;
+						failed_block_index2 = t;
+					}
+					raid6_2data_recov(raid_disks, chunk_size, failed_block_index1, failed_block_index2, (uint8_t**)blocks);
+				}
+			}
+			if(mlockall(MCL_CURRENT | MCL_FUTURE) != 0) {
+				err = 2;
+				goto exitCheck;
+			}
+			sig[0] = signal(SIGTERM, SIG_IGN);
+			sig[1] = signal(SIGINT, SIG_IGN);
+			sig[2] = signal(SIGQUIT, SIG_IGN);
+			rv = sysfs_set_num(info, NULL, "suspend_lo", start * chunk_size * data_disks);
+			rv |= sysfs_set_num(info, NULL, "suspend_hi", (start + 1) * chunk_size * data_disks);
+			lseek64(source[failed_disk1], offsets[failed_disk1] + start * chunk_size, 0);
+			write(source[failed_disk1], stripes[failed_disk1], chunk_size);
+			lseek64(source[failed_disk2], offsets[failed_disk2] + start * chunk_size, 0);
+			write(source[failed_disk2], stripes[failed_disk2], chunk_size);
+			rv |= sysfs_set_num(info, NULL, "suspend_lo", 0x7FFFFFFFFFFFFFFFULL);
+			rv |= sysfs_set_num(info, NULL, "suspend_hi", 0);
+			rv |= sysfs_set_num(info, NULL, "suspend_lo", 0);
+			signal(SIGQUIT, sig[2]);
+			signal(SIGINT, sig[1]);
+			signal(SIGTERM, sig[0]);
+			if(munlockall() != 0) {
+				err = 3;
+				goto exitCheck;
+			}
+
+			if(rv != 0) {
+				err = rv * 256;
+				goto exitCheck;
+			}
+		}
+
 
 		length--;
 		start++;
@@ -230,6 +320,8 @@ int main(int argc, char *argv[])
 	int chunk_size = 0;
 	int layout = -1;
 	int level = 6;
+	int repair = 0;
+	int failed_disk1, failed_disk2;
 	unsigned long long start, length;
 	int i;
 	int mdfd;
@@ -246,6 +338,7 @@ int main(int argc, char *argv[])
 
 	if (argc < 4) {
 		fprintf(stderr, "Usage: %s md_device start_stripe length_stripes\n", prg);
+		fprintf(stderr, "   or: %s md_device repair stripe failed_slot_1 failed_slot_2\n", prg);
 		exit_err = 1;
 		goto exitHere;
 	}
@@ -311,8 +404,38 @@ int main(int argc, char *argv[])
 	raid_disks = info->array.raid_disks;
 	chunk_size = info->array.chunk_size;
 	layout = info->array.layout;
-	start = getnum(argv[2], &err);
-	length = getnum(argv[3], &err);
+	if (strcmp(argv[2], "repair")==0) {
+		if (argc < 6) {
+			fprintf(stderr, "For repair mode, call %s md_device repair stripe failed_slot_1 failed_slot_2\n", prg);
+			exit_err = 1;
+			goto exitHere;
+		}
+		repair = 1;
+		start = getnum(argv[3], &err);
+		length = 1;
+		failed_disk1 = getnum(argv[4], &err);
+		failed_disk2 = getnum(argv[5], &err);
+
+		if(failed_disk1 > info->array.raid_disks) {
+			fprintf(stderr, "%s: failed_slot_1 index is higher than number of devices in raid\n", prg);
+			exit_err = 4;
+			goto exitHere;
+		}
+		if(failed_disk2 > info->array.raid_disks) {
+			fprintf(stderr, "%s: failed_slot_2 index is higher than number of devices in raid\n", prg);
+			exit_err = 4;
+			goto exitHere;
+		}
+		if(failed_disk1 == failed_disk2) {
+			fprintf(stderr, "%s: failed_slot_1 and failed_slot_2 are the same\n", prg);
+			exit_err = 4;
+			goto exitHere;
+		}
+	}
+	else {
+		start = getnum(argv[2], &err);
+		length = getnum(argv[3], &err);
+	}
 
 	if (err) {
 		fprintf(stderr, "%s: Bad number: %s\n", prg, err);
@@ -360,7 +483,7 @@ int main(int argc, char *argv[])
 
 	int rv = check_stripes(info, fds, offsets,
 			       raid_disks, chunk_size, level, layout,
-			       start, length, disk_name);
+			       start, length, disk_name, repair, failed_disk1, failed_disk2);
 	if (rv != 0) {
 		fprintf(stderr,
 			"%s: check_stripes returned %d\n", prg, rv);