4 files changed, 84 insertions, 14 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 2b30ffdb81b2..44bb1d52dd4c 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -607,6 +607,7 @@ void mddev_init(struct mddev *mddev)
         init_waitqueue_head(&mddev->sb_wait);
         init_waitqueue_head(&mddev->recovery_wait);
         mddev->reshape_position = MaxSector;
+        mddev->reshape_backwards = 0;
         mddev->resync_min = 0;
         mddev->resync_max = MaxSector;
         mddev->level = LEVEL_NONE;
@@ -1185,6 +1186,7 @@ static int super_90_validate(struct mddev *mddev, struct md_rdev *rdev)
                 mddev->events = ev1;
                 mddev->bitmap_info.offset = 0;
                 mddev->bitmap_info.default_offset = MD_SB_BYTES >> 9;
+                mddev->reshape_backwards = 0;
 
                 if (mddev->minor_version >= 91) {
                         mddev->reshape_position = sb->reshape_position;
@@ -1192,6 +1194,8 @@ static int super_90_validate(struct mddev *mddev, struct md_rdev *rdev)
                         mddev->new_level = sb->new_level;
                         mddev->new_layout = sb->new_layout;
                         mddev->new_chunk_sectors = sb->new_chunk >> 9;
+                        if (mddev->delta_disks < 0)
+                                mddev->reshape_backwards = 1;
                 } else {
                         mddev->reshape_position = MaxSector;
                         mddev->delta_disks = 0;
@@ -1645,7 +1649,8 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *rdev)
                 mddev->events = ev1;
                 mddev->bitmap_info.offset = 0;
                 mddev->bitmap_info.default_offset = 1024 >> 9;
-                
+                mddev->reshape_backwards = 0;
+
                 mddev->recovery_cp = le64_to_cpu(sb->resync_offset);
                 memcpy(mddev->uuid, sb->set_uuid, 16);
 
@@ -1662,6 +1667,11 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *rdev)
                         mddev->new_level = le32_to_cpu(sb->new_level);
                         mddev->new_layout = le32_to_cpu(sb->new_layout);
                         mddev->new_chunk_sectors = le32_to_cpu(sb->new_chunk);
+                        if (mddev->delta_disks < 0 ||
+                            (mddev->delta_disks == 0 &&
+                             (le32_to_cpu(sb->feature_map)
+                              & MD_FEATURE_RESHAPE_BACKWARDS)))
+                                mddev->reshape_backwards = 1;
                 } else {
                         mddev->reshape_position = MaxSector;
                         mddev->delta_disks = 0;
@@ -1781,6 +1791,10 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
                 sb->delta_disks = cpu_to_le32(mddev->delta_disks);
                 sb->new_level = cpu_to_le32(mddev->new_level);
                 sb->new_chunk = cpu_to_le32(mddev->new_chunk_sectors);
+                if (mddev->delta_disks == 0 &&
+                    mddev->reshape_backwards)
+                        sb->feature_map
+                                |= cpu_to_le32(MD_FEATURE_RESHAPE_BACKWARDS);
         }
 
         if (rdev->badblocks.count == 0)
@@ -3419,6 +3433,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
                 mddev->new_chunk_sectors = mddev->chunk_sectors;
                 mddev->raid_disks -= mddev->delta_disks;
                 mddev->delta_disks = 0;
+                mddev->reshape_backwards = 0;
                 module_put(pers->owner);
                 printk(KERN_WARNING "md: %s: %s would not accept array\n",
                        mdname(mddev), clevel);
@@ -3492,6 +3507,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
         mddev->layout = mddev->new_layout;
         mddev->chunk_sectors = mddev->new_chunk_sectors;
         mddev->delta_disks = 0;
+        mddev->reshape_backwards = 0;
         mddev->degraded = 0;
         if (mddev->pers->sync_request == NULL) {
                 /* this is now an array without redundancy, so
@@ -3585,6 +3601,7 @@ raid_disks_store(struct mddev *mddev, const char *buf, size_t len)
                 int olddisks = mddev->raid_disks - mddev->delta_disks;
                 mddev->delta_disks = n - olddisks;
                 mddev->raid_disks = n;
+                mddev->reshape_backwards = (mddev->delta_disks < 0);
         } else
                 mddev->raid_disks = n;
         return rv ? rv : len;
@@ -4436,6 +4453,7 @@ reshape_position_store(struct mddev *mddev, const char *buf, size_t len)
                 return -EINVAL;
         mddev->reshape_position = new;
         mddev->delta_disks = 0;
+        mddev->reshape_backwards = 0;
         mddev->new_level = mddev->level;
         mddev->new_layout = mddev->layout;
         mddev->new_chunk_sectors = mddev->chunk_sectors;
@@ -4447,6 +4465,42 @@ __ATTR(reshape_position, S_IRUGO|S_IWUSR, reshape_position_show,
        reshape_position_store);
 
 static ssize_t
+reshape_direction_show(struct mddev *mddev, char *page)
+{
+        return sprintf(page, "%s\n",
+                       mddev->reshape_backwards ? "backwards" : "forwards");
+}
+
+static ssize_t
+reshape_direction_store(struct mddev *mddev, const char *buf, size_t len)
+{
+        int backwards = 0;
+        if (cmd_match(buf, "forwards"))
+                backwards = 0;
+        else if (cmd_match(buf, "backwards"))
+                backwards = 1;
+        else
+                return -EINVAL;
+        if (mddev->reshape_backwards == backwards)
+                return len;
+
+        /* check if we are allowed to change */
+        if (mddev->delta_disks)
+                return -EBUSY;
+
+        if (mddev->persistent &&
+            mddev->major_version == 0)
+                return -EINVAL;
+
+        mddev->reshape_backwards = backwards;
+        return len;
+}
+
+static struct md_sysfs_entry md_reshape_direction =
+__ATTR(reshape_direction, S_IRUGO|S_IWUSR, reshape_direction_show,
+       reshape_direction_store);
+
+static ssize_t
 array_size_show(struct mddev *mddev, char *page)
 {
         if (mddev->external_size)
@@ -4501,6 +4555,7 @@ static struct attribute *md_default_attrs[] = {
         &md_safe_delay.attr,
         &md_array_state.attr,
         &md_reshape_position.attr,
+        &md_reshape_direction.attr,
         &md_array_size.attr,
         &max_corr_read_errors.attr,
         NULL,
@@ -5064,6 +5119,7 @@ static void md_clean(struct mddev *mddev)
         mddev->events = 0;
         mddev->can_decrease_events = 0;
         mddev->delta_disks = 0;
+        mddev->reshape_backwards = 0;
         mddev->new_level = LEVEL_NONE;
         mddev->new_layout = 0;
         mddev->new_chunk_sectors = 0;
@@ -5888,6 +5944,7 @@ static int set_array_info(struct mddev * mddev, mdu_array_info_t *info)
         mddev->new_chunk_sectors = mddev->chunk_sectors;
         mddev->new_layout = mddev->layout;
         mddev->delta_disks = 0;
+        mddev->reshape_backwards = 0;
 
         return 0;
 }
@@ -5953,10 +6010,16 @@ static int update_raid_disks(struct mddev *mddev, int raid_disks)
         if (mddev->sync_thread || mddev->reshape_position != MaxSector)
                 return -EBUSY;
         mddev->delta_disks = raid_disks - mddev->raid_disks;
+        if (mddev->delta_disks < 0)
+                mddev->reshape_backwards = 1;
+        else if (mddev->delta_disks > 0)
+                mddev->reshape_backwards = 0;
 
         rv = mddev->pers->check_reshape(mddev);
-        if (rv < 0)
+        if (rv < 0) {
                 mddev->delta_disks = 0;
+                mddev->reshape_backwards = 0;
+        }
         return rv;
 }
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 1c2063ccf48e..d51c0ca37777 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -262,6 +262,7 @@ struct mddev {
         sector_t                        reshape_position;
         int                             delta_disks, new_level, new_layout;
         int                             new_chunk_sectors;
+        int                             reshape_backwards;
 
         atomic_t                        plug_cnt;       /* If device is expecting
                                                          * more bios soon.
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index f351422938e0..0abbd3447cfb 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3970,13 +3970,13 @@ static void make_request(struct mddev *mddev, struct bio * bi)
                          * to check again.
                          */
                         spin_lock_irq(&conf->device_lock);
-                        if (mddev->delta_disks < 0
+                        if (mddev->reshape_backwards
                             ? logical_sector < conf->reshape_progress
                             : logical_sector >= conf->reshape_progress) {
                                 disks = conf->previous_raid_disks;
                                 previous = 1;
                         } else {
-                                if (mddev->delta_disks < 0
+                                if (mddev->reshape_backwards
                                     ? logical_sector < conf->reshape_safe
                                     : logical_sector >= conf->reshape_safe) {
                                         spin_unlock_irq(&conf->device_lock);
@@ -4009,7 +4009,7 @@ static void make_request(struct mddev *mddev, struct bio * bi)
                                  */
                                 int must_retry = 0;
                                 spin_lock_irq(&conf->device_lock);
-                                if (mddev->delta_disks < 0
+                                if (mddev->reshape_backwards
                                     ? logical_sector >= conf->reshape_progress
                                     : logical_sector < conf->reshape_progress)
                                         /* mismatch, need to try again */
@@ -4108,11 +4108,11 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
 
         if (sector_nr == 0) {
                 /* If restarting in the middle, skip the initial sectors */
-                if (mddev->delta_disks < 0 &&
+                if (mddev->reshape_backwards &&
                     conf->reshape_progress < raid5_size(mddev, 0, 0)) {
                         sector_nr = raid5_size(mddev, 0, 0)
                                 - conf->reshape_progress;
-                } else if (mddev->delta_disks >= 0 &&
+                } else if (!mddev->reshape_backwards &&
                            conf->reshape_progress > 0)
                         sector_nr = conf->reshape_progress;
                 sector_div(sector_nr, new_data_disks);
@@ -4147,7 +4147,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
         sector_div(readpos, data_disks);
         safepos = conf->reshape_safe;
         sector_div(safepos, data_disks);
-        if (mddev->delta_disks < 0) {
+        if (mddev->reshape_backwards) {
                 writepos -= min_t(sector_t, reshape_sectors, writepos);
                 readpos += reshape_sectors;
                 safepos += reshape_sectors;
@@ -4174,7 +4174,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
          * Maybe that number should be configurable, but I'm not sure it is
          * worth it.... maybe it could be a multiple of safemode_delay???
          */
-        if ((mddev->delta_disks < 0
+        if ((mddev->reshape_backwards
              ? (safepos > writepos && readpos < writepos)
              : (safepos < writepos && readpos > writepos)) ||
             time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
@@ -4195,7 +4195,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
                 sysfs_notify(&mddev->kobj, NULL, "sync_completed");
         }
 
-        if (mddev->delta_disks < 0) {
+        if (mddev->reshape_backwards) {
                 BUG_ON(conf->reshape_progress == 0);
                 stripe_addr = writepos;
                 BUG_ON((mddev->dev_sectors &
@@ -4239,7 +4239,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
                 list_add(&sh->lru, &stripes);
         }
         spin_lock_irq(&conf->device_lock);
-        if (mddev->delta_disks < 0)
+        if (mddev->reshape_backwards)
                 conf->reshape_progress -= reshape_sectors * new_data_disks;
         else
                 conf->reshape_progress += reshape_sectors * new_data_disks;
@@ -5008,7 +5008,7 @@ static int run(struct mddev *mddev)
                                        mdname(mddev));
                                 return -EINVAL;
                         }
-                } else if (mddev->delta_disks < 0
+                } else if (mddev->reshape_backwards
                     ? (here_new * mddev->new_chunk_sectors <=
                        here_old * mddev->chunk_sectors)
                     : (here_new * mddev->new_chunk_sectors >=
@@ -5535,7 +5535,7 @@ static int raid5_start_reshape(struct mddev *mddev)
         conf->chunk_sectors = mddev->new_chunk_sectors;
         conf->prev_algo = conf->algorithm;
         conf->algorithm = mddev->new_layout;
-        if (mddev->delta_disks < 0)
+        if (mddev->reshape_backwards)
                 conf->reshape_progress = raid5_size(mddev, 0, 0);
         else
                 conf->reshape_progress = 0;
@@ -5663,6 +5663,7 @@ static void raid5_finish_reshape(struct mddev *mddev)
                 mddev->chunk_sectors = conf->chunk_sectors;
                 mddev->reshape_position = MaxSector;
                 mddev->delta_disks = 0;
+                mddev->reshape_backwards = 0;
         }
 }
 
diff --git a/include/linux/raid/md_p.h b/include/linux/raid/md_p.h
index 8c0a3adc5df5..07e05f92d050 100644
--- a/include/linux/raid/md_p.h
+++ b/include/linux/raid/md_p.h
@@ -281,10 +281,15 @@ struct mdp_superblock_1 {
                                             * active device with same 'role'.
                                             * 'recovery_offset' is also set.
                                             */
+#define MD_FEATURE_RESHAPE_BACKWARDS    32 /* Reshape doesn't change number
+                                            * of devices, but is going
+                                            * backwards anyway.
+                                            */
 #define MD_FEATURE_ALL                  (MD_FEATURE_BITMAP_OFFSET       \
                                         |MD_FEATURE_RECOVERY_OFFSET     \
                                         |MD_FEATURE_RESHAPE_ACTIVE      \
                                         |MD_FEATURE_BAD_BLOCKS          \
-                                        |MD_FEATURE_REPLACEMENT)
+                                        |MD_FEATURE_REPLACEMENT         \
+                                        |MD_FEATURE_RESHAPE_BACKWARDS)
 
 #endif