From 199f1a1fadcd0fb5efba656ad92a44c51f8cc8ea Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Thu, 23 May 2013 15:48:48 +1000
Subject: [PATCH] Assemble: allow --update=revert-reshape

This will cause a reshape to start going backwards.
---
 Grow.c   |  3 ++-
 mdadm.c  |  4 +++-
 mdadm.h  |  5 +++++
 super0.c | 22 ++++++++++++++++++++++
 super1.c | 29 +++++++++++++++++++++++++++++
 5 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/Grow.c b/Grow.c
index 7b9cc70e..2eb8c7ce 100644
--- a/Grow.c
+++ b/Grow.c
@@ -2876,7 +2876,8 @@ started:
 	}
 
 	if (!backup_file)
-		switch(set_new_data_offset(sra, st, devname, info->delta_disks,
+		switch(set_new_data_offset(sra, st, devname,
+					   reshape.after.data_disks - reshape.before.data_disks,
 					   data_offset,
 					   reshape.min_offset_change)) {
 	case -1:
diff --git a/mdadm.c b/mdadm.c
index 83f1caa9..928d880b 100644
--- a/mdadm.c
+++ b/mdadm.c
@@ -757,6 +757,8 @@ int main(int argc, char *argv[])
 				continue;
 			if (strcmp(c.update, "metadata") == 0)
 				continue;
+			if (strcmp(c.update, "revert-reshape") == 0)
+				continue;
 			if (strcmp(c.update, "byteorder")==0) {
 				if (ss) {
 					pr_err("must not set metadata"
@@ -787,7 +789,7 @@ int main(int argc, char *argv[])
 			fprintf(outf, "Valid --update options are:\n"
 		"     'sparc2.2', 'super-minor', 'uuid', 'name', 'resync',\n"
 		"     'summaries', 'homehost', 'byteorder', 'devicesize',\n"
-		"     'no-bitmap', 'metadata'\n");
+		"     'no-bitmap', 'metadata', 'revert-reshape'\n");
 			exit(outf == stdout ? 0 : 2);
 
 		case O(MANAGE,'U'):
diff --git a/mdadm.h b/mdadm.h
index d97055ae..b7af65dc 100644
--- a/mdadm.h
+++ b/mdadm.h
@@ -736,6 +736,11 @@ extern struct superswitch {
 	 *   linear-grow-update - now change the size of the array.
 	 *   writemostly - set the WriteMostly1 bit in the superblock devflags
 	 *   readwrite - clear the WriteMostly1 bit in the superblock devflags
+	 *   no-bitmap - clear any record that a bitmap is present.
+	 *   bbl       - add a bad-block-log if possible
+	 *   no-bbl    - remove and bad-block-log is it is empty.
+	 *   revert-reshape - If a reshape is in progress, modify metadata so
+	 *                    it will resume going in the opposite direction.
 	 */
 	int (*update_super)(struct supertype *st, struct mdinfo *info,
 			    char *update,
diff --git a/super0.c b/super0.c
index 01c31c27..e4bbe3e1 100644
--- a/super0.c
+++ b/super0.c
@@ -645,6 +645,28 @@ static int update_super0(struct supertype *st, struct mdinfo *info,
 			uuid_from_super0(st, info->uuid);
 			st->other = super1_make_v0(st, info, st->sb);
 		}
+	} else if (strcmp(update, "revert-reshape") == 0) {
+		rv = -2;
+		if (sb->minor_version <= 90)
+			pr_err("No active reshape to revert on %s\n",
+			       devname);
+		else if (sb->delta_disks == 0)
+			pr_err("%s: Can on revert reshape which changes number of devices\n",
+			       devname);
+		else {
+			int tmp;
+			rv = 0;
+			sb->raid_disks -= sb->delta_disks;
+			sb->delta_disks = -sb->delta_disks;
+
+			tmp = sb->new_layout;
+			sb->new_layout = sb->layout;
+			sb->layout = tmp;
+
+			tmp = sb->new_chunk;
+			sb->new_chunk = sb->chunk_size;
+			sb->chunk_size = tmp;
+		}
 	} else if (strcmp(update, "no-bitmap") == 0) {
 		sb->state &= ~(1<<MD_SB_BITMAP_PRESENT);
 	} else if (strcmp(update, "_reshape_progress")==0)
diff --git a/super1.c b/super1.c
index a4677b9b..d92e5945 100644
--- a/super1.c
+++ b/super1.c
@@ -1252,6 +1252,35 @@ static int update_super1(struct supertype *st, struct mdinfo *info,
 			misc->device_size - __le64_to_cpu(sb->data_offset));
 		printf("Size is %llu\n", (unsigned long long)
 		       __le64_to_cpu(sb->data_size));
+	} else if (strcmp(update, "revert-reshape") == 0) {
+		rv = -2;
+		if (!(sb->feature_map & __cpu_to_le32(MD_FEATURE_RESHAPE_ACTIVE)))
+			pr_err("No active reshape to revert on %s\n",
+			       devname);
+		else {
+			rv = 0;
+			__u32 temp;
+			sb->raid_disks = __cpu_to_le32(__le32_to_cpu(sb->raid_disks) +
+						       __le32_to_cpu(sb->delta_disks));
+			if (sb->delta_disks == 0)
+				sb->feature_map ^= __cpu_to_le32(MD_FEATURE_RESHAPE_BACKWARDS);
+			else
+				sb->delta_disks = __cpu_to_le32(-__le32_to_cpu(sb->delta_disks));
+
+			temp = sb->new_layout;
+			sb->new_layout = sb->layout;
+			sb->layout = temp;
+
+			temp = sb->new_chunk;
+			sb->new_chunk = sb->chunksize;
+			sb->chunksize = temp;
+
+			if (sb->feature_map & __cpu_to_le32(MD_FEATURE_NEW_OFFSET)) {
+				sb->data_offset = __cpu_to_le64(__le64_to_cpu(sb->data_offset) +
+								(long)(int32_t)__le32_to_cpu(sb->new_offset));
+				sb->new_offset = __cpu_to_le32(-(int32_t)__le32_to_cpu(sb->new_offset));
+			}
+		}
 	} else if (strcmp(update, "_reshape_progress")==0)
 		sb->reshape_position = __cpu_to_le64(info->reshape_progress);
 	else if (strcmp(update, "writemostly")==0)
-- 
2.39.2