1 files changed, 447 insertions, 58 deletions

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 14835ae064c1..e4c41232107f 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -189,6 +189,7 @@ struct raid_dev {
 #define RT_FLAG_RS_RESUMED              1
 #define RT_FLAG_RS_BITMAP_LOADED        2
 #define RT_FLAG_UPDATE_SBS              3
+#define RT_FLAG_RESHAPE_RS              4
 
 /* Array elements of 64 bit needed for rebuild/write_mostly bits */
 #define DISKS_ARRAY_ELEMS ((MAX_RAID_DEVICES + (sizeof(uint64_t) * 8 - 1)) / sizeof(uint64_t) / 8)
@@ -206,6 +207,7 @@ struct raid_set {
         struct dm_target *ti;
 
         uint32_t bitmap_loaded;
+        uint32_t stripe_cache_entries;
         unsigned long ctr_flags;
         unsigned long runtime_flags;
 
@@ -219,25 +221,22 @@ struct raid_set {
         struct mddev md;
         struct raid_type *raid_type;
         struct dm_target_callbacks callbacks;
-        struct rs_layout rs_layout;
 
         struct raid_dev dev[0];
 };
 
-static void rs_config_backup(struct raid_set *rs)
+static void rs_config_backup(struct raid_set *rs, struct rs_layout *l)
 {
         struct mddev *mddev = &rs->md;
-        struct rs_layout *l = &rs->rs_layout;
 
         l->new_level = mddev->new_level;
         l->new_layout = mddev->new_layout;
         l->new_chunk_sectors = mddev->new_chunk_sectors;
 }
 
-static void rs_config_restore(struct raid_set *rs)
+static void rs_config_restore(struct raid_set *rs, struct rs_layout *l)
 {
         struct mddev *mddev = &rs->md;
-        struct rs_layout *l = &rs->rs_layout;
 
         mddev->new_level = l->new_level;
         mddev->new_layout = l->new_layout;
@@ -336,6 +335,12 @@ static bool rs_is_raid0(struct raid_set *rs)
         return !rs->md.level;
 }
 
+/* Return true, if raid set in @rs is raid1 */
+static bool rs_is_raid1(struct raid_set *rs)
+{
+        return rs->md.level == 1;
+}
+
 /* Return true, if raid set in @rs is raid10 */
 static bool rs_is_raid10(struct raid_set *rs)
 {
@@ -356,6 +361,20 @@ static bool rs_is_reshapable(struct raid_set *rs)
                (rs_is_raid10(rs) && !__is_raid10_far(rs->md.new_layout));
 }
 
+/* Return true, if raid set in @rs is recovering */
+static bool rs_is_recovering(struct raid_set *rs)
+{
+        smp_rmb();
+        return rs->md.recovery_cp != MaxSector;
+}
+
+/* Return true, if raid set in @rs is reshaping */
+static bool rs_is_reshaping(struct raid_set *rs)
+{
+        smp_rmb();
+        return rs->md.reshape_position != MaxSector;
+}
+
 /*
  * bool helpers to test for various raid levels of a raid type
  */
@@ -591,6 +610,24 @@ static struct raid_type *get_raid_type_by_ll(const int level, const int layout)
 }
 
 /*
+ * Conditionally change bdev capacity of @rs
+ * in case of a disk add/remove reshape
+ */
+static void rs_set_capacity(struct raid_set *rs)
+{
+        struct mddev *mddev = &rs->md;
+
+        /* Make sure we access most actual mddev properties */
+        smp_rmb();
+        if (rs->ti->len != mddev->array_sectors && !rs_is_reshaping(rs)) {
+                struct gendisk *gendisk = dm_disk(dm_table_get_md(rs->ti->table));
+
+                set_capacity(gendisk, mddev->array_sectors);
+                revalidate_disk(gendisk);
+        }
+}
+
+/*
  * Set the mddev properties in @rs to the current
  * ones retrieved from the freshest superblock
  */
@@ -642,6 +679,7 @@ static struct raid_set *raid_set_alloc(struct dm_target *ti, struct raid_type *r
 
         rs->ti = ti;
         rs->raid_type = raid_type;
+        rs->stripe_cache_entries = 256;
         rs->md.raid_disks = raid_devs;
         rs->md.level = raid_type->level;
         rs->md.new_level = rs->md.level;
@@ -874,7 +912,7 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
 static int validate_raid_redundancy(struct raid_set *rs)
 {
         unsigned i, rebuild_cnt = 0;
-        unsigned rebuilds_per_group = 0, copies, d;
+        unsigned rebuilds_per_group = 0, copies;
         unsigned group_size, last_group_start;
 
         for (i = 0; i < rs->md.raid_disks; i++)
@@ -894,7 +932,7 @@ static int validate_raid_redundancy(struct raid_set *rs)
                         goto too_many;
                 break;
         case 10:
-                copies = raid10_md_layout_to_copies(rs->md.layout);
+                copies = raid10_md_layout_to_copies(rs->md.new_layout);
                 if (rebuild_cnt < copies)
                         break;
 
@@ -912,12 +950,11 @@ static int validate_raid_redundancy(struct raid_set *rs)
                  *          A    A    B    B    C
                  *          C    D    D    E    E
                  */
-                if (!strcmp("near", raid10_md_layout_to_format(rs->md.layout))) {
-                        for (i = 0; i < rs->md.raid_disks * copies; i++) {
+                if (__is_raid10_near(rs->md.new_layout)) {
+                        for (i = 0; i < rs->raid_disks; i++) {
                                 if (!(i % copies))
                                         rebuilds_per_group = 0;
-                                d = i % rs->md.raid_disks;
-                                if ((!rs->dev[d].rdev.sb_page ||
+                                if ((!rs->dev[i].rdev.sb_page ||
                                     !test_bit(In_sync, &rs->dev[i].rdev.flags)) &&
                                     (++rebuilds_per_group >= copies))
                                         goto too_many;
@@ -986,10 +1023,10 @@ too_many:
 static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                              unsigned num_raid_params)
 {
-        int raid10_format = ALGORITHM_RAID10_DEFAULT;
+        int value, raid10_format = ALGORITHM_RAID10_DEFAULT;
         unsigned raid10_copies = 2;
         unsigned i;
-        unsigned value, region_size = 0;
+        unsigned region_size = 0;
         sector_t max_io_len;
         const char *arg, *key;
         struct raid_dev *rd;
@@ -998,7 +1035,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
         arg = dm_shift_arg(as);
         num_raid_params--; /* Account for chunk_size argument */
 
-        if (kstrtouint(arg, 10, &value) < 0) {
+        if (kstrtoint(arg, 10, &value) < 0) {
                 rs->ti->error = "Bad numerical argument given for chunk_size";
                 return -EINVAL;
         }
@@ -1105,7 +1142,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                         continue;
                 }
 
-                if (kstrtouint(arg, 10, &value) < 0) {
+                if (kstrtoint(arg, 10, &value) < 0) {
                         rs->ti->error = "Bad numerical argument given in raid params";
                         return -EINVAL;
                 }
@@ -1207,21 +1244,12 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                                 return -EINVAL;
                         }
 
-                        /*
-                         * In device-mapper, we specify things in sectors, but
-                         * MD records this value in kB
-                         */
-                        value /= 2;
-
                         if (!rt_is_raid456(rt)) {
                                 rs->ti->error = "Inappropriate argument: stripe_cache";
                                 return -EINVAL;
                         }
-                        if (raid5_set_cache_size(&rs->md, (int)value)) {
-                                rs->ti->error = "Bad stripe_cache size";
-                                return -EINVAL;
-                        }
 
+                        rs->stripe_cache_entries = value;
                 } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_MIN_RECOVERY_RATE))) {
                         if (test_and_set_bit(__CTR_FLAG_MIN_RECOVERY_RATE, &rs->ctr_flags)) {
                                 rs->ti->error = "Only one min_recovery_rate argument pair allowed";
@@ -1303,8 +1331,6 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                         rs->ti->error = "RAID10 format 'near' and 'raid10_use_near_sets' are incompatible";
                         return -EINVAL;
                 }
-
-                rs->md.layout = rs->md.new_layout;
         }
 
         rs->raid10_copies = raid10_copies;
@@ -1317,6 +1343,46 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
         return rs_check_for_valid_flags(rs);
 }
 
+/* Set raid4/5/6 cache size */
+static int rs_set_raid456_stripe_cache(struct raid_set *rs)
+{
+        int r;
+        struct r5conf *conf;
+        struct mddev *mddev = &rs->md;
+        uint32_t min_stripes = max(mddev->chunk_sectors, mddev->new_chunk_sectors) / 2;
+        uint32_t nr_stripes = rs->stripe_cache_entries;
+
+        if (!rt_is_raid456(rs->raid_type)) {
+                rs->ti->error = "Inappropriate raid level; cannot change stripe_cache size";
+                return -EINVAL;
+        }
+
+        if (nr_stripes < min_stripes) {
+                DMINFO("Adjusting requested %u stripe cache entries to %u to suit stripe size",
+                       nr_stripes, min_stripes);
+                nr_stripes = min_stripes;
+        }
+
+        conf = mddev->private;
+        if (!conf) {
+                rs->ti->error = "Cannot change stripe_cache size on inactive RAID set";
+                return -EINVAL;
+        }
+
+        /* Try setting number of stripes in raid456 stripe cache */
+        if (conf->min_nr_stripes != nr_stripes) {
+                r = raid5_set_cache_size(mddev, nr_stripes);
+                if (r) {
+                        rs->ti->error = "Failed to set raid4/5/6 stripe cache size";
+                        return r;
+                }
+
+                DMINFO("%u stripe cache entries", nr_stripes);
+        }
+
+        return 0;
+}
+
 /* Return # of data stripes as kept in mddev as of @rs (i.e. as of superblock) */
 static unsigned int mddev_data_stripes(struct raid_set *rs)
 {
@@ -1337,6 +1403,7 @@ static int rs_set_dev_and_array_sectors(struct raid_set *rs, bool use_mddev)
         struct mddev *mddev = &rs->md;
         struct md_rdev *rdev;
         sector_t array_sectors = rs->ti->len, dev_sectors = rs->ti->len;
+        sector_t cur_dev_sectors = rs->dev[0].rdev.sectors;
 
         if (use_mddev) {
                 delta_disks = mddev->delta_disks;
@@ -1377,6 +1444,9 @@ static int rs_set_dev_and_array_sectors(struct raid_set *rs, bool use_mddev)
         mddev->array_sectors = array_sectors;
         mddev->dev_sectors = dev_sectors;
 
+        if (!rs_is_raid0(rs) && dev_sectors > cur_dev_sectors)
+                mddev->recovery_cp = dev_sectors;
+
         return 0;
 bad:
         rs->ti->error = "Target length not divisible by number of data devices";
@@ -1387,6 +1457,7 @@ static void do_table_event(struct work_struct *ws)
 {
         struct raid_set *rs = container_of(ws, struct raid_set, md.event_work);
 
+        rs_set_capacity(rs);
         dm_table_event(rs->ti->table);
 }
 
@@ -1410,6 +1481,17 @@ static int rs_check_takeover(struct raid_set *rs)
         struct mddev *mddev = &rs->md;
         unsigned int near_copies;
 
+        smp_rmb();
+        if (rs->md.degraded) {
+                rs->ti->error = "Can't takeover degraded raid set";
+                return -EPERM;
+        }
+
+        if (rs_is_reshaping(rs)) {
+                rs->ti->error = "Can't takeover reshaping raid set";
+                return -EPERM;
+        }
+
         switch (mddev->level) {
         case 0:
                 /* raid0 -> raid1/5 with one disk */
@@ -1419,7 +1501,7 @@ static int rs_check_takeover(struct raid_set *rs)
 
                 /* raid0 -> raid10 */
                 if (mddev->new_level == 10 &&
-                    !(rs->raid_disks % 2))
+                    !(rs->raid_disks % mddev->raid_disks))
                         return 0;
 
                 /* raid0 with multiple disks -> raid4/5/6 */
@@ -1658,6 +1740,39 @@ struct dm_raid_superblock {
         /* Always set rest up to logical block size to 0 when writing (see get_metadata_device() below). */
 } __packed;
 
+/*
+ * Check for reshape constraints on raid set @rs:
+ *
+ * - reshape function non-existent
+ * - degraded set
+ * - ongoing recovery
+ * - ongoing reshape
+ *
+ * Returns 0 if none or -EPERM if given constraint
+ * and error message reference in @errmsg
+ */
+static int rs_check_reshape(struct raid_set *rs)
+{
+        struct mddev *mddev = &rs->md;
+
+        smp_rmb(); /* Make sure we access recent reshape position */
+
+        if (!mddev->pers || !mddev->pers->check_reshape)
+                rs->ti->error = "Reshape not supported";
+        else if (mddev->degraded)
+                rs->ti->error = "Can't reshape degraded raid set";
+        else if (rs_is_recovering(rs))
+                rs->ti->error = "Convert request on recovering raid set prohibited";
+        else if (mddev->reshape_position && rs_is_reshaping(rs))
+                rs->ti->error = "raid set already reshaping!";
+        else if (!(rs_is_raid10(rs) || rs_is_raid456(rs)))
+                rs->ti->error = "Reshaping only supported for raid4/5/6/10";
+        else
+                return 0;
+
+        return -EPERM;
+}
+
 static int read_disk_sb(struct md_rdev *rdev, int size)
 {
         BUG_ON(!rdev->sb_page);
@@ -1936,6 +2051,10 @@ static int super_init_validation(struct raid_set *rs, struct md_rdev *rdev)
          *    and the new device needs to be rebuilt - in which
          *    case the In_sync bit will /not/ be set and
          *    recovery_cp must be MaxSector.
+         * 3) This is/are a new device(s) being added to an old
+         *    raid set during takeover to a higher raid level
+         *    to provide capacity for redundancy or during reshape
+         *    to add capacity to grow the raid set.
          */
         d = 0;
         rdev_for_each(r, mddev) {
@@ -1961,9 +2080,9 @@ static int super_init_validation(struct raid_set *rs, struct md_rdev *rdev)
                 if (new_devs == rs->raid_disks) {
                         DMINFO("Superblocks created for new raid set");
                         set_bit(MD_ARRAY_FIRST_USE, &mddev->flags);
-                        set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
                         mddev->recovery_cp = 0;
-                } else if (new_devs && new_devs != rs->raid_disks && !rebuilds) {
+                } else if (new_devs != rebuilds &&
+                           new_devs != rs->delta_disks) {
                         DMERR("New device injected into existing raid set without "
                               "'delta_disks' or 'rebuild' parameter specified");
                         return -EINVAL;
@@ -1978,12 +2097,13 @@ static int super_init_validation(struct raid_set *rs, struct md_rdev *rdev)
                         DMERR("new device%s provided without 'rebuild'",
                               new_devs > 1 ? "s" : "");
                         return -EINVAL;
-                } else if (mddev->recovery_cp != MaxSector) {
+                } else if (rs_is_recovering(rs)) {
                         DMERR("'rebuild' specified while raid set is not in-sync (recovery_cp=%llu)",
                               (unsigned long long) mddev->recovery_cp);
                         return -EINVAL;
-                } else if (mddev->reshape_position != MaxSector) {
-                        DMERR("'rebuild' specified while raid set is being reshaped");
+                } else if (rs_is_reshaping(rs)) {
+                        DMERR("'rebuild' specified while raid set is being reshaped (reshape_position=%llu)",
+                              (unsigned long long) mddev->reshape_position);
                         return -EINVAL;
                 }
         }
@@ -2082,7 +2202,7 @@ static int super_validate(struct raid_set *rs, struct md_rdev *rdev)
                  * If no reshape in progress -> we're recovering single
                  * disk(s) and have to set the device(s) to out-of-sync
                  */
-                else if (rs->md.reshape_position == MaxSector)
+                else if (!rs_is_reshaping(rs))
                         clear_bit(In_sync, &rdev->flags); /* Mandatory for recovery */
         }
 
@@ -2181,15 +2301,13 @@ static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
          * Validation of the freshest device provides the source of
          * validation for the remaining devices.
          */
-        if (super_validate(rs, freshest)) {
-                rs->ti->error = "Unable to assemble array: Invalid superblocks";
+        rs->ti->error = "Unable to assemble array: Invalid superblocks";
+        if (super_validate(rs, freshest))
                 return -EINVAL;
-        }
 
         rdev_for_each(rdev, mddev)
                 if ((rdev != freshest) && super_validate(rs, rdev))
                         return -EINVAL;
-
         return 0;
 }
 
@@ -2344,6 +2462,106 @@ static int rs_setup_takeover(struct raid_set *rs)
 }
 
 /*
+ *
+ * - change raid layout
+ * - change chunk size
+ * - add disks
+ * - remove disks
+ */
+static int rs_setup_reshape(struct raid_set *rs)
+{
+        int r = 0;
+        unsigned int cur_raid_devs, d;
+        struct mddev *mddev = &rs->md;
+        struct md_rdev *rdev;
+
+        mddev->delta_disks = rs->delta_disks;
+        cur_raid_devs = mddev->raid_disks;
+
+        /* Ignore impossible layout change whilst adding/removing disks */
+        if (mddev->delta_disks &&
+            mddev->layout != mddev->new_layout) {
+                DMINFO("Ignoring invalid layout change with delta_disks=%d", rs->delta_disks);
+                mddev->new_layout = mddev->layout;
+        }
+
+        /*
+         * Adjust array size:
+         *
+         * - in case of adding disks, array size has
+         *   to grow after the disk adding reshape,
+         *   which'll hapen in the event handler;
+         *   reshape will happen forward, so space has to
+         *   be available at the beginning of each disk
+         *
+         * - in case of removing disks, array size
+         *   has to shrink before starting the reshape,
+         *   which'll happen here;
+         *   reshape will happen backward, so space has to
+         *   be available at the end of each disk
+         *
+         * - data_offset and new_data_offset are
+         *   adjusted for afreentioned out of place
+         *   reshaping based on userspace passing in
+         *   the "data_offset <sectors>" key/value
+         *   pair via te constructor
+         */
+
+        /* Add disk(s) */
+        if (rs->delta_disks > 0) {
+                /* Prepare disks for check in raid4/5/6/10 {check|start}_reshape */
+                for (d = cur_raid_devs; d < rs->raid_disks; d++) {
+                        rdev = &rs->dev[d].rdev;
+                        clear_bit(In_sync, &rdev->flags);
+
+                        /*
+                         * save_raid_disk needs to be -1, or recovery_offset will be set to 0
+                         * by md, which'll store that erroneously in the superblock on reshape
+                         */
+                        rdev->saved_raid_disk = -1;
+                        rdev->raid_disk = d;
+
+                        rdev->sectors = mddev->dev_sectors;
+                        rdev->recovery_offset = MaxSector;
+                }
+
+                mddev->reshape_backwards = 0; /* adding disks -> forward reshape */
+
+        /* Remove disk(s) */
+        } else if (rs->delta_disks < 0) {
+                r = rs_set_dev_and_array_sectors(rs, true);
+                mddev->reshape_backwards = 1; /* removing disk(s) -> backward reshape */
+
+        /* Change layout and/or chunk size */
+        } else {
+                /*
+                 * Reshape layout (e.g. raid5_ls -> raid5_n) and/or chunk size:
+                 *
+                 * keeping number of disks and do layout change ->
+                 *
+                 * toggle reshape_backward depending on data_offset:
+                 *
+                 * - free space upfront -> reshape forward
+                 *
+                 * - free space at the end -> reshape backward
+                 *
+                 *
+                 * This utilizes free reshape space avoiding the need
+                 * for userspace to move (parts of) LV segments in
+                 * case of layout/chunksize change  (for disk
+                 * adding/removing reshape space has to be at
+                 * the proper address (see above with delta_disks):
+                 *
+                 * add disk(s)   -> begin
+                 * remove disk(s)-> end
+                 */
+                mddev->reshape_backwards = rs->dev[0].rdev.data_offset ? 0 : 1;
+        }
+
+        return r;
+}
+
+/*
  * Enable/disable discard support on RAID set depending on
  * RAID level and discard properties of underlying RAID members.
  */
@@ -2411,6 +2629,7 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
         unsigned num_raid_params, num_raid_devs;
         struct raid_set *rs = NULL;
         const char *arg;
+        struct rs_layout rs_layout;
         struct dm_arg_set as = { argc, argv }, as_nrd;
         struct dm_arg _args[] = {
                 { 0, as.argc, "Cannot understand number of raid parameters" },
@@ -2469,7 +2688,7 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
          * requested to be able to compare to superblock
          * members for conversion decisions.
          */
-        rs_config_backup(rs);
+        rs_config_backup(rs, &rs_layout);
 
         r = analyse_superblocks(ti, rs);
         if (r)
@@ -2480,13 +2699,23 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
         ti->num_flush_bios = 1;
 
         /* Restore any requested new layout for conversion decision */
-        rs_config_restore(rs);
+        rs_config_restore(rs, &rs_layout);
 
-        /*
-         * If a takeover is needed, just set the level to
-         * the new requested one and allow the raid set to run.
-         */
-        if (rs_takeover_requested(rs)) {
+        if (test_bit(MD_ARRAY_FIRST_USE, &rs->md.flags)) {
+                set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
+                rs_set_new(rs);
+        } else if (rs_is_reshaping(rs))
+                ; /* skip rs setup */
+        else if (rs_takeover_requested(rs)) {
+                if (rs_is_reshaping(rs)) {
+                        ti->error = "Can't takeover a reshaping raid set";
+                        return -EPERM;
+                }
+
+                /*
+                 * If a takeover is needed, just set the level to
+                 * the new requested one and allow the raid set to run.
+                 */
                 r = rs_check_takeover(rs);
                 if (r)
                         return r;
@@ -2495,11 +2724,55 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 if (r)
                         return r;
 
-                /* Tell preresume to update superblocks with new layout */
                 set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
                 rs_set_new(rs);
         } else if (rs_reshape_requested(rs)) {
-                rs_set_cur(rs); /* Dummy to reject, fill in */
+                if (rs_is_reshaping(rs)) {
+                        ti->error = "raid set already reshaping!";
+                        return -EPERM;
+                }
+
+                if (rs_is_raid10(rs)) {
+                        if (rs->raid_disks != rs->md.raid_disks &&
+                            __is_raid10_near(rs->md.layout) &&
+                            rs->raid10_copies &&
+                            rs->raid10_copies != __raid10_near_copies(rs->md.layout)) {
+                                /*
+                                 * raid disk have to be multiple of data copies to allow this conversion,
+                                 *
+                                 * This is actually not a reshape it is a
+                                 * rebuild of any additional mirrors per group
+                                 */
+                                if (rs->raid_disks % rs->raid10_copies) {
+                                        ti->error = "Can't reshape raid10 mirror groups";
+                                        return -EINVAL;
+                                }
+
+                                /* Userpace reordered disks to add/remove mirrors -> adjust raid_disk indexes */
+                                __reorder_raid_disk_indexes(rs);
+                                rs->md.layout = raid10_format_to_md_layout(rs, ALGORITHM_RAID10_NEAR,
+                                                                           rs->raid10_copies);
+                                rs->md.new_layout = rs->md.layout;
+
+                        } else
+                                set_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags);
+
+                } else if (rs_is_raid456(rs))
+                        set_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags);
+
+                /*
+                 * HM FIXME: process raid1 via delta_disks as well?
+                 *           Would cause allocations in raid1->check_reshape
+                 *           though, thus more issues with potential failures
+                 */
+                else if (rs_is_raid1(rs))
+                        rs->md.raid_disks = rs->raid_disks;
+
+                if (rs->md.raid_disks < rs->raid_disks)
+                        set_bit(MD_ARRAY_FIRST_USE, &rs->md.flags);
+
+                set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
+                rs_set_cur(rs);
         } else
                 rs_set_cur(rs);
 
@@ -2517,25 +2790,46 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
         mddev_lock_nointr(&rs->md);
         r = md_run(&rs->md);
         rs->md.in_sync = 0; /* Assume already marked dirty */
-        mddev_unlock(&rs->md);
 
         if (r) {
-                ti->error = "Fail to run raid array";
+                ti->error = "Failed to run raid array";
+                mddev_unlock(&rs->md);
                 goto bad;
         }
 
-        if (ti->len != rs->md.array_sectors) {
-                ti->error = "Array size does not match requested target length";
-                r = -EINVAL;
-                goto size_mismatch;
-        }
         rs->callbacks.congested_fn = raid_is_congested;
         dm_table_add_target_callbacks(ti->table, &rs->callbacks);
 
         mddev_suspend(&rs->md);
+
+        /* Try to adjust the raid4/5/6 stripe cache size to the stripe size */
+        if (rs_is_raid456(rs)) {
+                r = rs_set_raid456_stripe_cache(rs);
+                if (r)
+                        goto bad_stripe_cache;
+        }
+
+        /* Now do an early reshape check */
+        if (test_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags)) {
+                r = rs_check_reshape(rs);
+                if (r)
+                        return r;
+
+                /* Restore new, ctr requested layout to perform check */
+                rs_config_restore(rs, &rs_layout);
+
+                r = rs->md.pers->check_reshape(&rs->md);
+                if (r) {
+                        ti->error = "Reshape check failed";
+                        goto bad_check_reshape;
+                }
+        }
+
+        mddev_unlock(&rs->md);
         return 0;
 
-size_mismatch:
+bad_stripe_cache:
+bad_check_reshape:
         md_stop(&rs->md);
 bad:
         raid_set_free(rs);
@@ -2557,6 +2851,17 @@ static int raid_map(struct dm_target *ti, struct bio *bio)
         struct raid_set *rs = ti->private;
         struct mddev *mddev = &rs->md;
 
+        /*
+         * If we're reshaping to add disk(s)), ti->len and
+         * mddev->array_sectors will differ during the process
+         * (ti->len > mddev->array_sectors), so we have to requeue
+         * bios with addresses > mddev->array_sectors here or
+         * or there will occur accesses past EOD of the component
+         * data images thus erroring the raid set.
+         */
+        if (unlikely(bio_end_sector(bio) > mddev->array_sectors))
+                return DM_MAPIO_REQUEUE;
+
         mddev->pers->make_request(mddev, bio);
 
         return DM_MAPIO_SUBMITTED;
@@ -2709,7 +3014,7 @@ static void raid_status(struct dm_target *ti, status_type_t type,
                 if (!rt)
                         return;
 
-                DMEMIT("%s %d ", rt ? rt->name : "unknown", mddev->raid_disks);
+                DMEMIT("%s %d ", rt->name, mddev->raid_disks);
 
                 /* Access most recent mddev properties for status output */
                 smp_rmb();
@@ -2718,7 +3023,7 @@ static void raid_status(struct dm_target *ti, status_type_t type,
                                       mddev->resync_max_sectors : mddev->dev_sectors;
                 progress = rs_get_progress(rs, resync_max_sectors, &array_in_sync);
                 resync_mismatches = (mddev->last_sync_action && !strcasecmp(mddev->last_sync_action, "check")) ?
-                                    (unsigned int) atomic64_read(&mddev->resync_mismatches) : 0;
+                                    atomic64_read(&mddev->resync_mismatches) : 0;
                 sync_action = decipher_sync_action(&rs->md);
 
                 /* HM FIXME: do we want another state char for raid0? It shows 'D' or 'A' now */
@@ -2925,6 +3230,8 @@ static void raid_postsuspend(struct dm_target *ti)
         struct raid_set *rs = ti->private;
 
         mddev_suspend(&rs->md);
+        rs->md.ro = 1;
+        clear_bit(RT_FLAG_RS_RESUMED, &rs->runtime_flags);
 }
 
 static void attempt_restore_of_faulty_devices(struct raid_set *rs)
@@ -2999,8 +3306,64 @@ static int __load_dirty_region_bitmap(struct raid_set *rs)
         return r;
 }
 
+/*
+ * Reshape changes raid algorithm of @rs to new one within personality
+ * (e.g. raid6_zr -> raid6_nc), changes stripe size, adds/removes
+ * disks from a raid set thus growing/shrinking it or resizes the set
+ *
+ * Call mddev_lock_nointr() before!
+ */
+static int rs_start_reshape(struct raid_set *rs)
+{
+        int r;
+        struct mddev *mddev = &rs->md;
+        struct md_personality *pers = mddev->pers;
+
+        r = rs_setup_reshape(rs);
+        if (r)
+                return r;
+
+        /* Need to be resumed to be able to start reshape, recovery is frozen until raid_resume() though */
+        if (mddev->suspended)
+                mddev_resume(mddev);
+
+        /*
+         * Check any reshape constraints enforced by the personalility
+         *
+         * May as well already kick the reshape off so that * pers->start_reshape() becomes optional.
+         */
+        r = pers->check_reshape(mddev);
+        if (r) {
+                rs->ti->error = "pers->check_reshape() failed";
+                return r;
+        }
+
+        /*
+         * Personality may not provide start reshape method in which
+         * case check_reshape above has already covered everything
+         */
+        if (pers->start_reshape) {
+                r = pers->start_reshape(mddev);
+                if (r) {
+                        rs->ti->error = "pers->start_reshape() failed";
+                        return r;
+                }
+        }
+
+        /* Suspend because a resume will happen in raid_resume() */
+        if (!mddev->suspended)
+                mddev_suspend(mddev);
+
+        mddev->ro = 0;
+        md_update_sb(mddev, 1);
+        mddev->ro = 1;
+
+        return 0;
+}
+
 static int raid_preresume(struct dm_target *ti)
 {
+        int r;
         struct raid_set *rs = ti->private;
         struct mddev *mddev = &rs->md;
 
@@ -3034,7 +3397,33 @@ static int raid_preresume(struct dm_target *ti)
         configure_discard_support(rs);
 
         /* Load the bitmap from disk unless raid0 */
-        return __load_dirty_region_bitmap(rs);
+        r = __load_dirty_region_bitmap(rs);
+        if (r)
+                return r;
+
+        /* Check for any resize/reshape on @rs and adjust/initiate */
+        /* Be prepared for mddev_resume() in raid_resume() */
+        set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+        if (mddev->recovery_cp && mddev->recovery_cp < MaxSector) {
+                set_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);
+                set_bit(MD_RECOVERY_SYNC, &mddev->recovery);
+                mddev->resync_min = mddev->recovery_cp;
+        }
+
+        rs_set_capacity(rs);
+
+        /* Check for any reshape request and region size change unless new raid set */
+        if (test_and_clear_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags)) {
+                /* Initiate a reshape. */
+                mddev_lock_nointr(mddev);
+                r = rs_start_reshape(rs);
+                mddev_unlock(mddev);
+                if (r)
+                        DMWARN("Failed to check/start reshape, continuing without change");
+                r = 0;
+        }
+
+        return r;
 }
 
 static void raid_resume(struct dm_target *ti)