dm raid: add reshaping support to the target
authorHeinz Mauelshagen <heinzm@redhat.com>
Mon, 13 Jun 2016 15:55:14 +0000 (17:55 +0200)
committerMike Snitzer <snitzer@redhat.com>
Tue, 14 Jun 2016 22:52:12 +0000 (18:52 -0400)
Add bool functions rs_is_recovering and rs_is_reshaping()
to test for ongoing recovery/reshaping respectively in order
to reject respective requests on ongoing ones.

Remove ctr array size check, because ti->len and array
sectors will differ during disk addition/removal reshape.

Use __is_raid10_near() rather than type string compare.

Introduce rs_check_reshape() and rs_start_reshape(),
use the former in the ctr to reject bogus rehsape requests
and the latter in preresume to actually start a reshape.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
drivers/md/dm-raid.c

index 14835ae..e4c4123 100644 (file)
@@ -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
  */
@@ -590,6 +609,24 @@ static struct raid_type *get_raid_type_by_ll(const int level, const int layout)
        return NULL;
 }
 
+/*
+ * 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;
 }
 
@@ -2343,6 +2461,106 @@ static int rs_setup_takeover(struct raid_set *rs)
        return 0;
 }
 
+/*
+ *
+ * - 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)