raid6check: various cleanup/fixes

- document meaning of various arrays. In particular:
   stripes[]
   blocks[]
   blocks_page[]
   block_index_for_slot[]

  It needs to be clear if these are indexed by raid_disk
  number or syndrome number.

- changed meaning of block_index_for_slot[].  It didn't seem
  to be used consistently.  It also made use of the block numbers
  in array data ordering, which is not directly relevant for syndrome
  calculations.

- reduced number of args to autorepair and manual_repair
  There don't need both stripes[] and blocks[].  And they don't need
  diskP or diskQ.
  blocks[-1] is the P chunk, blocks[-2] is the Q chunk.
  block_index_for_slot[] can be used to find the target device for
  a particular syndrome block.

- remove stripe locking from within manual_repair, and instead
  use the global stripe locking used for check and autorepair.

- this necessitated changes to raid6_datap_recov and raid5_2data_reov
  so the P and Q blocks could be before or after the data blocks.



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

2 files changed, 168 insertions, 129 deletions

diff --git a/raid6check.c b/raid6check.c
index 6909b50..f019440 100644
--- a/raid6check.c
+++ b/raid6check.c
@@ -44,9 +44,10 @@ int is_ddf(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_datap_recov(int disks, size_t bytes, int faila, uint8_t **ptrs,
+		       int neg_offset);
 void raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
-		       uint8_t **ptrs);
+		       uint8_t **ptrs, int neg_offset);
 void xor_blocks(char *target, char **sources, int disks, int size);
 
 /* Collect per stripe consistency information */
@@ -160,38 +161,39 @@ int unlock_all_stripes(struct mdinfo *info, sighandler_t *sig) {
 }
 
 /* Autorepair */
-int autorepair(int *disk, int diskP, int diskQ, unsigned long long start, int chunk_size,
-		char *name[], int raid_disks, int data_disks, char **blocks_page,
-		char **blocks, uint8_t *p, char **stripes, int *block_index_for_slot,
+int autorepair(int *disk, unsigned long long start, int chunk_size,
+		char *name[], int raid_disks, int syndrome_disks, char **blocks_page,
+		char **blocks, uint8_t *p, int *block_index_for_slot,
 		int *source, unsigned long long *offsets)
 {
 	int i, j;
 	int pages_to_write_count = 0;
 	int page_to_write[chunk_size >> CHECK_PAGE_BITS];
 	for(j = 0; j < (chunk_size >> CHECK_PAGE_BITS); j++) {
-		if (disk[j] >= 0) {
-			printf("Auto-repairing slot %d (%s)\n", disk[j], name[disk[j]]);
+		if (disk[j] >= -2 && block_index_for_slot[disk[j]] >= 0) {
+			int slot = block_index_for_slot[disk[j]];
+			printf("Auto-repairing slot %d (%s)\n", slot, name[slot]);
 			pages_to_write_count++;
 			page_to_write[j] = 1;
-			for(i = 0; i < raid_disks; i++) {
+			for(i = -2; i < syndrome_disks; i++) {
 				blocks_page[i] = blocks[i] + j * CHECK_PAGE_SIZE;
 			}
-			if (disk[j] == diskQ) {
-				qsyndrome(p, (uint8_t*)stripes[diskQ] + j * CHECK_PAGE_SIZE, (uint8_t**)blocks_page, data_disks, CHECK_PAGE_SIZE);
+			if (disk[j] == -2) {
+				qsyndrome(p, (uint8_t*)blocks_page[-2],
+					  (uint8_t**)blocks_page,
+					  syndrome_disks, CHECK_PAGE_SIZE);
 			}
 			else {
-				char *all_but_failed_blocks[data_disks];
-				int failed_block_index = block_index_for_slot[disk[j]];
-				for(i = 0; i < data_disks; i++) {
-					if (failed_block_index == i) {
-						all_but_failed_blocks[i] = stripes[diskP] + j * CHECK_PAGE_SIZE;
-					}
-					else {
+				char *all_but_failed_blocks[syndrome_disks];
+				for(i = 0; i < syndrome_disks; i++) {
+					if (i == disk[j])
+						all_but_failed_blocks[i] = blocks_page[-1];
+					else
 						all_but_failed_blocks[i] = blocks_page[i];
-					}
 				}
-				xor_blocks(stripes[disk[j]] + j * CHECK_PAGE_SIZE,
-				all_but_failed_blocks, data_disks, CHECK_PAGE_SIZE);
+				xor_blocks(blocks_page[disk[j]],
+					   all_but_failed_blocks, syndrome_disks,
+					   CHECK_PAGE_SIZE);
 			}
 		}
 		else {
@@ -203,8 +205,11 @@ int autorepair(int *disk, int diskP, int diskQ, unsigned long long start, int ch
 		int write_res = 0;
 		for(j = 0; j < (chunk_size >> CHECK_PAGE_BITS); j++) {
 			if(page_to_write[j] == 1) {
-				lseek64(source[disk[j]], offsets[disk[j]] + start * chunk_size + j * CHECK_PAGE_SIZE, SEEK_SET);
-				write_res += write(source[disk[j]], stripes[disk[j]] + j * CHECK_PAGE_SIZE, CHECK_PAGE_SIZE);
+				int slot = block_index_for_slot[disk[j]];
+				lseek64(source[slot], offsets[slot] + start * chunk_size + j * CHECK_PAGE_SIZE, SEEK_SET);
+				write_res += write(source[slot],
+						   blocks[disk[j]] + j * CHECK_PAGE_SIZE,
+						   CHECK_PAGE_SIZE);
 			}
 		}
 
@@ -218,101 +223,83 @@ int autorepair(int *disk, int diskP, int diskQ, unsigned long long start, int ch
 }
 
 /* Manual repair */
-int manual_repair(int diskP, int diskQ, int chunk_size, int raid_disks, int data_disks,
-		  int failed_disk1, int failed_disk2, unsigned long long start, int *block_index_for_slot,
-		  char *name[], char **stripes, char **blocks, uint8_t *p, struct mdinfo *info, sighandler_t *sig,
+int manual_repair(int chunk_size, int syndrome_disks,
+		  int failed_slot1, int failed_slot2,
+		  unsigned long long start, int *block_index_for_slot,
+		  char *name[], char **stripes, char **blocks, uint8_t *p,
 		  int *source, unsigned long long *offsets)
 {
-	int err = 0;
 	int i;
+	int fd1 = block_index_for_slot[failed_slot1];
+	int fd2 = block_index_for_slot[failed_slot2];
 	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]);
+	       fd1, name[fd1],
+	       fd2, name[fd2]);
 
-	if (failed_disk1 == diskQ || failed_disk2 == diskQ) {
-		char *all_but_failed_blocks[data_disks];
+	if (failed_slot1 == -2 || failed_slot2 == -2) {
+		char *all_but_failed_blocks[syndrome_disks];
 		int failed_data_or_p;
-		int failed_block_index;
 
-		if (failed_disk1 == diskQ) {
-			failed_data_or_p = failed_disk2;
-		}
-		else {
-			failed_data_or_p = failed_disk1;
-		}
+		if (failed_slot1 == -2)
+			failed_data_or_p = failed_slot2;
+		else
+			failed_data_or_p = failed_slot1;
+
 		printf("Repairing D/P(%d) and Q\n", failed_data_or_p);
-		failed_block_index = block_index_for_slot[failed_data_or_p];
-		for (i = 0; i < data_disks; i++) {
-			if (failed_block_index == i) {
-				all_but_failed_blocks[i] = stripes[diskP];
-			}
-			else {
+
+		for (i = 0; i < syndrome_disks; i++) {
+			if (i == failed_data_or_p)
+				all_but_failed_blocks[i] = blocks[-1];
+			else
 				all_but_failed_blocks[i] = blocks[i];
-			}
 		}
-		xor_blocks(stripes[failed_data_or_p],
-			   all_but_failed_blocks, data_disks, chunk_size);
-		qsyndrome(p, (uint8_t*)stripes[diskQ], (uint8_t**)blocks, data_disks, chunk_size);
-	}
-	else {
+		xor_blocks(blocks[failed_data_or_p],
+			   all_but_failed_blocks, syndrome_disks, chunk_size);
+		qsyndrome(p, (uint8_t*)blocks[-2], (uint8_t**)blocks,
+			  syndrome_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 = block_index_for_slot[failed_data];
-			printf("Repairing D(%d) and P\n", failed_data);
-			raid6_datap_recov(raid_disks, chunk_size, failed_block_index, (uint8_t**)blocks);
-		}
-		else {
+		if (failed_slot1 == -1 || failed_slot2 == -1) {
+			int failed_data;
+			if (failed_slot1 == -1)
+				failed_data = failed_slot2;
+			else
+				failed_data = failed_slot1;
+				printf("Repairing D(%d) and P\n", failed_data);
+			raid6_datap_recov(syndrome_disks+2, chunk_size,
+					  failed_data, (uint8_t**)blocks, 1);
+		} else {
 			printf("Repairing D and D\n");
-			int failed_block_index1 = block_index_for_slot[failed_disk1];
-			int failed_block_index2 = block_index_for_slot[failed_disk2];
-			if (failed_block_index1 > failed_block_index2) {
-				int t = failed_block_index1;
-				failed_block_index1 = failed_block_index2;
-				failed_block_index2 = t;
+			if (failed_slot1 > failed_slot2) {
+				int t = failed_slot1;
+				failed_slot1 = failed_slot2;
+				failed_slot2 = t;
 			}
-			raid6_2data_recov(raid_disks, chunk_size, failed_block_index1, failed_block_index2, (uint8_t**)blocks);
+			raid6_2data_recov(syndrome_disks+2, chunk_size,
+					  failed_slot1, failed_slot2,
+					  (uint8_t**)blocks, 1);
 		}
 	}
 
-	err = lock_stripe(info, start, chunk_size, data_disks, sig);
-	if(err != 0) {
-		if (err != 2) {
-			return -1;
-		}
-		return -2;;
-	}
-
 	int write_res1, write_res2;
 	off64_t seek_res;
 
-	seek_res = lseek64(source[failed_disk1],
-			   offsets[failed_disk1] + start * chunk_size, SEEK_SET);
+	seek_res = lseek64(source[fd1],
+			   offsets[fd1] + start * chunk_size, SEEK_SET);
 	if (seek_res < 0) {
 		fprintf(stderr, "lseek failed for failed_disk1\n");
 		return -1;
 	}
-	write_res1 = write(source[failed_disk1], stripes[failed_disk1], chunk_size);
+	write_res1 = write(source[fd1], blocks[failed_slot1], chunk_size);
 
-	seek_res = lseek64(source[failed_disk2],
-			   offsets[failed_disk2] + start * chunk_size, SEEK_SET);
+	seek_res = lseek64(source[fd2],
+			   offsets[fd2] + start * chunk_size, SEEK_SET);
 	if (seek_res < 0) {
-		fprintf(stderr, "lseek failed for failed_disk1\n");
+		fprintf(stderr, "lseek failed for failed_disk2\n");
 		return -1;
 	}
-	write_res2 = write(source[failed_disk2], stripes[failed_disk2], chunk_size);
-
-	err = unlock_all_stripes(info, sig);
-	if(err != 0) {
-		return -2;
-	}
+	write_res2 = write(source[fd2], blocks[failed_slot2], chunk_size);
 
 	if (write_res1 != chunk_size || write_res2 != chunk_size) {
 		fprintf(stderr, "Failed to write a complete chunk.\n");
@@ -331,10 +318,27 @@ int check_stripes(struct mdinfo *info, int *source, unsigned long long *offsets,
 	int data_disks = raid_disks - 2;
 	int syndrome_disks = data_disks + is_ddf(layout) * 2;
 	char *stripe_buf = xmalloc(raid_disks * chunk_size);
+
+	/* stripes[] is indexed by raid_disk and holds chunks from each device */
 	char **stripes = xmalloc(raid_disks * sizeof(char*));
+
+	/* blocks[] is indexed by syndrome number and points to either one of the
+	 * chunks from 'stripes[]', or to a chunk of zeros. -1 and -2 are
+	 * P and Q */
 	char **blocks = xmalloc((syndrome_disks + 2) * sizeof(char*));
-	char **blocks_page = xmalloc(raid_disks * sizeof(char*));
+
+	/* blocks_page[] is a temporary index to just one page of the chunks
+	 * that blocks[] points to. */
+	char **blocks_page = xmalloc((syndrome_disks + 2) * sizeof(char*));
+
+	/* block_index_for_slot[] provides the reverse mapping from blocks to stripes.
+	 * The index is a syndrome position, the content is a raid_disk number.
+	 * indicies -1 and -2 work, and are P and Q disks */
 	int *block_index_for_slot = xmalloc((syndrome_disks+2) * sizeof(int));
+
+	/* 'p' and 'q' contain calcualted P and Q, to be compared with
+	 * blocks[-1] and blocks[-2];
+	 */
 	uint8_t *p = xmalloc(chunk_size);
 	uint8_t *q = xmalloc(chunk_size);
 	char *zero = xmalloc(chunk_size);
@@ -350,11 +354,19 @@ int check_stripes(struct mdinfo *info, int *source, unsigned long long *offsets,
 	if (!tables_ready)
 		make_tables();
 
+	block_index_for_slot += 2;
+	blocks += 2;
+	blocks_page += 2;
+
 	memset(zero, 0, chunk_size);
 	for ( i = 0 ; i < raid_disks ; i++)
 		stripes[i] = stripe_buf + i * chunk_size;
 
 	while (length > 0) {
+		/* The syndrome number of the broken disk is recorded
+		 * in 'disk[]' which allows a different broken disk for
+		 * each page.
+		 */
 		int disk[chunk_size >> CHECK_PAGE_BITS];
 
 		err = lock_stripe(info, start, chunk_size, data_disks, sig);
@@ -382,7 +394,13 @@ int check_stripes(struct mdinfo *info, int *source, unsigned long long *offsets,
 		}
 
 		diskP = geo_map(-1, start, raid_disks, level, layout);
+		block_index_for_slot[-1] = diskP;
+		blocks[-1] = stripes[diskP];
+
 		diskQ = geo_map(-2, start, raid_disks, level, layout);
+		block_index_for_slot[-2] = diskQ;
+		blocks[-2] = stripes[diskQ];
+
 		if (!is_ddf(layout)) {
 			/* The syndrome-order of disks starts immediately after 'Q',
 			 * but skips P */
@@ -396,46 +414,47 @@ int check_stripes(struct mdinfo *info, int *source, unsigned long long *offsets,
 				if (diskD >= raid_disks)
 					diskD = 0;
 				blocks[i] = stripes[diskD];
-				block_index_for_slot[diskD] = i;
+				block_index_for_slot[i] = diskD;
 			}
 		} else {
 			/* The syndrome-order exactly follows raid-disk
 			 * numbers, with ZERO in place of P and Q
 			 */
-			for (i = 0 ; i < raid_disks; i++)
-				if (i == diskP || i == diskQ)
+			for (i = 0 ; i < raid_disks; i++) {
+				if (i == diskP || i == diskQ) {
 					blocks[i] = zero;
-				else
+					block_index_for_slot[i] = -1;
+				} else {
 					blocks[i] = stripes[i];
+					block_index_for_slot[i] = i;
+				}
+			}
 		}
 
 		qsyndrome(p, q, (uint8_t**)blocks, syndrome_disks, chunk_size);
-		blocks[syndrome_disks] = stripes[diskP];
-		block_index_for_slot[diskP] = data_disks;
-		blocks[syndrome_disks+1] = stripes[diskQ];
-		block_index_for_slot[diskQ] = data_disks+1;
 
 		raid6_collect(chunk_size, p, q, stripes[diskP], stripes[diskQ], results);
 		raid6_stats(disk, results, raid_disks, chunk_size);
 
 		for(j = 0; j < (chunk_size >> CHECK_PAGE_BITS); j++) {
 			int role = disk[j];
-			if(disk[j] >= -2) {
-				disk[j] = geo_map(disk[j], start, raid_disks, level, layout);
-			}
-			if(disk[j] >= 0) {
-				printf("Error detected at stripe %llu, page %d: possible failed disk slot %d: %d --> %s\n",
-				       start, j, role, disk[j], name[disk[j]]);
-			}
-			if(disk[j] == -65535) {
+			if (role >= -2) {
+				int slot = block_index_for_slot[role];
+				if (slot >= 0)
+					printf("Error detected at stripe %llu, page %d: possible failed disk slot %d: %d --> %s\n",
+					       start, j, role, slot, name[slot]);
+				else
+					printf("Error detected at stripe %llu, page %d: failed slot %d should be zeros\n",
+					       start, j, role);
+			} else if(disk[j] == -65535) {
 				printf("Error detected at stripe %llu, page %d: disk slot unknown\n", start, j);
 			}
 		}
 
 		if(repair == AUTO_REPAIR) {
-			err = autorepair(disk, diskP, diskQ, start, chunk_size,
-					name, raid_disks, data_disks, blocks_page,
-					blocks, p, stripes, block_index_for_slot,
+			err = autorepair(disk, start, chunk_size,
+					name, raid_disks, syndrome_disks, blocks_page,
+					blocks, p, block_index_for_slot,
 					source, offsets);
 			if(err != 0) {
 				unlock_all_stripes(info, sig);
@@ -443,22 +462,30 @@ int check_stripes(struct mdinfo *info, int *source, unsigned long long *offsets,
 			}
 		}
 
-		err = unlock_all_stripes(info, sig);
-		if(err != 0) {
-			goto exitCheck;
-		}
-
 		if(repair == MANUAL_REPAIR) {
-			err = manual_repair(diskP, diskQ, chunk_size, raid_disks, data_disks,
-					failed_disk1, failed_disk2, start, block_index_for_slot,
-					name, stripes, blocks, p, info, sig,
-					source, offsets);
+			int failed_slot1 = -1, failed_slot2 = -1;
+			for (i = -2; i < syndrome_disks; i++) {
+				if (block_index_for_slot[i] == failed_disk1)
+					failed_slot1 = i;
+				if (block_index_for_slot[i] == failed_disk2)
+					failed_slot2 = i;
+			}
+			err = manual_repair(chunk_size, syndrome_disks,
+					    failed_slot1, failed_slot2,
+					    start, block_index_for_slot,
+					    name, stripes, blocks, p,
+					    source, offsets);
 			if(err == -1) {
 				unlock_all_stripes(info, sig);
 				goto exitCheck;
 			}
 		}
 
+		err = unlock_all_stripes(info, sig);
+		if(err != 0) {
+			goto exitCheck;
+		}
+
 		length--;
 		start++;
 	}
@@ -467,9 +494,9 @@ exitCheck:
 
 	free(stripe_buf);
 	free(stripes);
-	free(blocks);
-	free(blocks_page);
-	free(block_index_for_slot);
+	free(blocks-2);
+	free(blocks_page-2);
+	free(block_index_for_slot-2);
 	free(p);
 	free(q);
 	free(results);
diff --git a/restripe.c b/restripe.c
index 40d6061..1c859a3 100644
--- a/restripe.c
+++ b/restripe.c
@@ -345,16 +345,22 @@ void ensure_zero_has_size(int chunk_size)
 /* Following was taken from linux/drivers/md/raid6recov.c */
 
 /* Recover two failed data blocks. */
+
 void raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
-		       uint8_t **ptrs)
+		       uint8_t **ptrs, int neg_offset)
 {
 	uint8_t *p, *q, *dp, *dq;
 	uint8_t px, qx, db;
 	const uint8_t *pbmul;	/* P multiplier table for B data */
 	const uint8_t *qmul;		/* Q multiplier table (for both) */
 
-	p = ptrs[disks-2];
-	q = ptrs[disks-1];
+	if (neg_offset) {
+		p = ptrs[-1];
+		q = ptrs[-2];
+	} else {
+		p = ptrs[disks-2];
+		q = ptrs[disks-1];
+	}
 
 	/* Compute syndrome with zero for the missing data pages
 	   Use the dead data pages as temporary storage for
@@ -385,13 +391,19 @@ void raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
 }
 
 /* Recover failure of one data block plus the P block */
-void raid6_datap_recov(int disks, size_t bytes, int faila, uint8_t **ptrs)
+void raid6_datap_recov(int disks, size_t bytes, int faila, uint8_t **ptrs,
+		       int neg_offset)
 {
 	uint8_t *p, *q, *dq;
 	const uint8_t *qmul;		/* Q multiplier table */
 
-	p = ptrs[disks-2];
-	q = ptrs[disks-1];
+	if (neg_offset) {
+		p = ptrs[-1];
+		q = ptrs[-2];
+	} else {
+		p = ptrs[disks-2];
+		q = ptrs[disks-1];
+	}
 
 	/* Compute syndrome with zero for the missing data page
 	   Use the dead data page as temporary storage for delta q */
@@ -637,7 +649,7 @@ int save_stripes(int *source, unsigned long long *offsets,
 			if (fblock[1] == data_disks)
 				/* One data failed, and parity failed */
 				raid6_datap_recov(syndrome_disks+2, chunk_size,
-						  fdisk[0], bufs);
+						  fdisk[0], bufs, 0);
 			else {
 				if (fdisk[0] > fdisk[1]) {
 					int t = fdisk[0];
@@ -646,7 +658,7 @@ int save_stripes(int *source, unsigned long long *offsets,
 				}
 				/* Two data blocks failed, P,Q OK */
 				raid6_2data_recov(syndrome_disks+2, chunk_size,
-						  fdisk[0], fdisk[1], bufs);
+						  fdisk[0], fdisk[1], bufs, 0);
 			}
 		}
 		if (dest) {