analyse_change: fix calculation of after.data_disks and ->delta_disks.

When changing level when a new number of raid disks was explicitly
specified, we much make sure that the change implied by the
change in level is properly incorporated into the final result.

So explicitly track the change in number of parity disks
(delta_parity) and use it together with delta_disks to determine
final data_disks.
Also set info->delta_disks so other code doesn't need to mirror
this analysis.

And add some errors in cases where a new number of disks was
requested but is not currently supported

Reported-by: Adam Kwolek <adam.kwolek@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 34 insertions, 26 deletions

diff --git a/Grow.c b/Grow.c
index 49831ad7..424d4892 100644
--- a/Grow.c
+++ b/Grow.c
@@ -893,6 +893,10 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 	 * when assembling an array that is undergoing reshape.
 	 */
 	int new_disks;
+	/* delta_parity records change in number of devices
+	 * caused by level change
+	 */
+	int delta_parity = 0;
 
 	/* If a new level not explicitly given, we assume no-change */
 	if (info->new_level == UnSet)
@@ -925,6 +929,10 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		 * raid0 with 1 disk
 		 */
 		if (info->new_level == 0) {
+			if (info->delta_disks != UnSet &&
+			    info->delta_disks != 0)
+				return "Cannot change number of disks "
+					"with RAID1->RAID0 conversion";
 			re->level = 0;
 			re->before.data_disks = 1;
 			re->after.data_disks = 1;
@@ -944,6 +952,10 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		}
 		if (info->array.raid_disks == 2 &&
 		    info->new_level == 5) {
+			if (info->delta_disks != UnSet &&
+			    info->delta_disks != 0)
+				return "Cannot change number of disks "
+					"with RAID1->RAID5 conversion";
 			re->level = 5;
 			re->before.data_disks = 1;
 			re->after.data_disks = 1;
@@ -970,10 +982,10 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 			return "RAID10 can only be changed to RAID0";
 		new_disks = (info->array.raid_disks
 			     / (info->array.layout & 0xff));
-		if (info->delta_disks == UnSet) {
+		if (info->delta_disks == UnSet)
 			info->delta_disks = (new_disks
 					     - info->array.raid_disks);
-		}
+
 		if (info->delta_disks != new_disks - info->array.raid_disks)
 			return "New number of raid-devices impossible for RAID10";
 		if (info->new_chunk &&
@@ -1032,16 +1044,19 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		 * a raid4 style layout of the final level.
 		 */
 		switch (info->new_level) {
-		case 0:
 		case 4:
+			delta_parity = 1;
+		case 0:
 			re->level = 4;
 			re->before.layout = 0;
 			break;
 		case 5:
+			delta_parity = 1;
 			re->level = 5;
 			re->before.layout = ALGORITHM_PARITY_N;
 			break;
 		case 6:
+			delta_parity = 2;
 			re->level = 6;
 			re->before.layout = ALGORITHM_PARITY_N;
 			break;
@@ -1057,6 +1072,7 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 	case 5:
 		switch (info->new_level) {
 		case 0:
+			delta_parity = -1;
 		case 4:
 			re->level = info->array.level;
 			re->before.data_disks = info->array.raid_disks - 1;
@@ -1068,6 +1084,7 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 			re->before.layout = info->array.layout;
 			break;
 		case 6:
+			delta_parity = 1;
 			re->level = 6;
 			re->before.data_disks = info->array.raid_disks - 1;
 			switch (info->array.layout) {
@@ -1096,6 +1113,10 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		case 1:
 			if (info->array.raid_disks != 2)
 				return "Can only convert a 2-device array to RAID1";
+			if (info->delta_disks != UnSet &&
+			    info->delta_disks != 0)
+				return "Cannot set raid_disk when "
+					"converting RAID5->RAID1";
 			re->level = 1;
 			break;
 		default:
@@ -1106,6 +1127,7 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		switch (info->new_level) {
 		case 4:
 		case 5:
+			delta_parity = -1;
 		case 6:
 			re->level = 6;
 			re->before.data_disks = info->array.raid_disks - 2;
@@ -1131,11 +1153,7 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		 */
 		if (re->level != 4 && re->level != 5)
 			return "Cannot covert to RAID0 from this level";
-		if (info->delta_disks == UnSet)
-			re->after.data_disks = re->before.data_disks;
-		else
-			re->after.data_disks =
-				info->array.raid_disks + info->delta_disks;
+
 		switch (re->level) {
 		case 4:
 			re->after.layout = 0 ; break;
@@ -1148,11 +1166,7 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		/* We can only get to RAID4 from RAID5 */
 		if (re->level != 4 && re->level != 5)
 			return "Cannot convert to RAID4 from this level";
-		if (info->delta_disks == UnSet)
-			re->after.data_disks = re->before.data_disks;
-		else
-			re->after.data_disks =
-				re->before.data_disks + info->delta_disks;
+
 		switch (re->level) {
 		case 4:
 			re->after.layout = 0 ; break;
@@ -1165,14 +1179,7 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		/* We get to RAID5 for RAID5 or RAID6 */
 		if (re->level != 5 && re->level != 6)
 			return "Cannot convert to RAID5 from this level";
-		if (info->delta_disks == UnSet)
-			re->after.data_disks = re->before.data_disks;
-		else if (re->level == 5)
-			re->after.data_disks =
-				re->before.data_disks + info->delta_disks;
-		else
-			re->after.data_disks =
-				info->array.raid_disks + info->delta_disks - 1;
+
 		switch (re->level) {
 		case 5:
 			if (info->new_layout == UnSet)
@@ -1205,11 +1212,6 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 		/* We must already be at level 6 */
 		if (re->level != 6)
 			return "Impossible level change";
-		if (info->delta_disks == UnSet)
-			re->after.data_disks = re->before.data_disks;
-		else
-			re->after.data_disks = (info->array.raid_disks +
-						info->delta_disks) - 2;
 		if (info->new_layout == UnSet)
 			re->after.layout = info->array.layout;
 		else
@@ -1218,6 +1220,12 @@ char *analyse_change(struct mdinfo *info, struct reshape *re)
 	default:
 		return "Impossible level change requested";
 	}
+	if (info->delta_disks == UnSet)
+		info->delta_disks = delta_parity;
+
+	re->after.data_disks = (re->before.data_disks
+				+ info->delta_disks
+				- delta_parity);
 	switch (re->level) {
 	case 6: re->parity = 2; break;
 	case 4: