dm raid: introduce extended superblock and new raid types to support takeover/reshaping

Add new members to the dm-raid superblock and new raid types to support
takeover/reshape.

Add all necessary members needed to support takeover and reshape in one
go -- aiming to limit the amount of changes to the superblock layout.

This is a larger patch due to the new superblock members, their related
flags, validation of both and involved API additions/changes:

 - add additional members to keep track of:
   - state about forward/backward reshaping
   - reshape position
   - new level, layout, stripe size and delta disks
   - data offset to current and new data for out-of-place reshapes
   - failed devices bitfield extensions to keep track of max raid devices

 - adjust super_validate() to cope with new superblock members

 - adjust super_init_validation() to cope with new superblock members

 - add definitions for ctr flags supporting delta disks etc.

 - add new raid types (raid6_n_6 etc.)

 - add new raid10 supporting function API (_is_raid10_*())

 - adjust to changed raid10 supporting function API

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 471 insertions, 133 deletions

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 719612440dfc..c98c34c4d284 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -63,6 +63,10 @@ struct raid_dev {
 #define CTR_FLAG_REGION_SIZE       0x200 /* 2 */ /* Not with raid0! */
 #define CTR_FLAG_RAID10_COPIES     0x400 /* 2 */ /* Only with raid10 */
 #define CTR_FLAG_RAID10_FORMAT     0x800 /* 2 */ /* Only with raid10 */
+/* New for v1.8.0 */
+#define CTR_FLAG_DELTA_DISKS          0x1000 /* 2 */ /* Only with reshapable raid4/5/6/10! */
+#define CTR_FLAG_DATA_OFFSET          0x2000 /* 2 */ /* Only with reshapable raid4/5/6/10! */
+#define CTR_FLAG_RAID10_USE_NEAR_SETS 0x4000 /* 2 */ /* Only with raid10! */
 
 /*
  * Definitions of various constructor flags to
@@ -73,7 +77,8 @@ struct raid_dev {
 #define CTR_FLAGS_ANY_SYNC              (CTR_FLAG_SYNC | CTR_FLAG_NOSYNC)
 
 /* Define flags for options without argument (e.g. 'nosync') */
-#define CTR_FLAG_OPTIONS_NO_ARGS        CTR_FLAGS_ANY_SYNC
+#define CTR_FLAG_OPTIONS_NO_ARGS        (CTR_FLAGS_ANY_SYNC | \
+                                         CTR_FLAG_RAID10_USE_NEAR_SETS)
 
 /* Define flags for options with one argument (e.g. 'delta_disks +2') */
 #define CTR_FLAG_OPTIONS_ONE_ARG (CTR_FLAG_REBUILD | \
@@ -85,7 +90,9 @@ struct raid_dev {
                                   CTR_FLAG_STRIPE_CACHE | \
                                   CTR_FLAG_REGION_SIZE | \
                                   CTR_FLAG_RAID10_COPIES | \
-                                  CTR_FLAG_RAID10_FORMAT)
+                                  CTR_FLAG_RAID10_FORMAT | \
+                                  CTR_FLAG_DELTA_DISKS | \
+                                  CTR_FLAG_DATA_OFFSET)
 
 /* All ctr optional arguments */
 #define ALL_CTR_FLAGS           (CTR_FLAG_OPTIONS_NO_ARGS | \
@@ -99,7 +106,9 @@ struct raid_dev {
 /* "raid1" does not accept stripe cache or any raid10 options */
 #define RAID1_INVALID_FLAGS     (CTR_FLAG_STRIPE_CACHE | \
                                  CTR_FLAG_RAID10_COPIES | \
-                                 CTR_FLAG_RAID10_FORMAT)
+                                 CTR_FLAG_RAID10_FORMAT | \
+                                 CTR_FLAG_DELTA_DISKS | \
+                                 CTR_FLAG_DATA_OFFSET)
 
 /* "raid10" does not accept any raid1 or stripe cache options */
 #define RAID10_INVALID_FLAGS    (CTR_FLAG_WRITE_MOSTLY | \
@@ -115,16 +124,24 @@ struct raid_dev {
 #define RAID45_INVALID_FLAGS    (CTR_FLAG_WRITE_MOSTLY | \
                                  CTR_FLAG_MAX_WRITE_BEHIND | \
                                  CTR_FLAG_RAID10_FORMAT | \
-                                 CTR_FLAG_RAID10_COPIES)
+                                 CTR_FLAG_RAID10_COPIES | \
+                                 CTR_FLAG_RAID10_USE_NEAR_SETS)
 #define RAID6_INVALID_FLAGS     (CTR_FLAG_NOSYNC | RAID45_INVALID_FLAGS)
 /* ...invalid options definitions per raid level */
 
+/* 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)
+
 struct raid_set {
         struct dm_target *ti;
 
         uint32_t bitmap_loaded;
         uint32_t ctr_flags;
 
+        int raid_disks;
+        int delta_disks;
+        int raid10_copies;
+
         struct mddev md;
         struct raid_type *raid_type;
         struct dm_target_callbacks callbacks;
@@ -132,6 +149,12 @@ struct raid_set {
         struct raid_dev dev[0];
 };
 
+/* raid10 algorithms (i.e. formats) */
+#define ALGORITHM_RAID10_DEFAULT        0
+#define ALGORITHM_RAID10_NEAR           1
+#define ALGORITHM_RAID10_OFFSET         2
+#define ALGORITHM_RAID10_FAR            3
+
 /* Supported raid types and properties. */
 static struct raid_type {
         const char *name;               /* RAID algorithm. */
@@ -141,17 +164,26 @@ static struct raid_type {
         const unsigned level;           /* RAID level. */
         const unsigned algorithm;       /* RAID algorithm. */
 } raid_types[] = {
-        {"raid0",    "RAID0 (striping)",                0, 2, 0, 0 /* NONE */},
-        {"raid1",    "RAID1 (mirroring)",               0, 2, 1, 0 /* NONE */},
-        {"raid10",   "RAID10 (striped mirrors)",        0, 2, 10, UINT_MAX /* Varies */},
-        {"raid4",    "RAID4 (dedicated parity disk)",   1, 2, 5, ALGORITHM_PARITY_0},
-        {"raid5_la", "RAID5 (left asymmetric)",         1, 2, 5, ALGORITHM_LEFT_ASYMMETRIC},
-        {"raid5_ra", "RAID5 (right asymmetric)",        1, 2, 5, ALGORITHM_RIGHT_ASYMMETRIC},
-        {"raid5_ls", "RAID5 (left symmetric)",          1, 2, 5, ALGORITHM_LEFT_SYMMETRIC},
-        {"raid5_rs", "RAID5 (right symmetric)",         1, 2, 5, ALGORITHM_RIGHT_SYMMETRIC},
-        {"raid6_zr", "RAID6 (zero restart)",            2, 4, 6, ALGORITHM_ROTATING_ZERO_RESTART},
-        {"raid6_nr", "RAID6 (N restart)",               2, 4, 6, ALGORITHM_ROTATING_N_RESTART},
-        {"raid6_nc", "RAID6 (N continue)",              2, 4, 6, ALGORITHM_ROTATING_N_CONTINUE}
+        {"raid0",         "raid0 (striping)",                       0, 2, 0,  0 /* NONE */},
+        {"raid1",         "raid1 (mirroring)",                      0, 2, 1,  0 /* NONE */},
+        {"raid10_far",    "raid10 far (striped mirrors)",           0, 2, 10, ALGORITHM_RAID10_FAR},
+        {"raid10_offset", "raid10 offset (striped mirrors)",        0, 2, 10, ALGORITHM_RAID10_OFFSET},
+        {"raid10_near",   "raid10 near (striped mirrors)",          0, 2, 10, ALGORITHM_RAID10_NEAR},
+        {"raid10",        "raid10 (striped mirrors)",               0, 2, 10, ALGORITHM_RAID10_DEFAULT},
+        {"raid4",         "raid4 (dedicated last parity disk)",     1, 2, 4,  ALGORITHM_PARITY_N}, /* raid4 layout = raid5_n */
+        {"raid5_n",       "raid5 (dedicated last parity disk)",     1, 2, 5,  ALGORITHM_PARITY_N},
+        {"raid5_ls",      "raid5 (left symmetric)",                 1, 2, 5,  ALGORITHM_LEFT_SYMMETRIC},
+        {"raid5_rs",      "raid5 (right symmetric)",                1, 2, 5,  ALGORITHM_RIGHT_SYMMETRIC},
+        {"raid5_la",      "raid5 (left asymmetric)",                1, 2, 5,  ALGORITHM_LEFT_ASYMMETRIC},
+        {"raid5_ra",      "raid5 (right asymmetric)",               1, 2, 5,  ALGORITHM_RIGHT_ASYMMETRIC},
+        {"raid6_zr",      "raid6 (zero restart)",                   2, 4, 6,  ALGORITHM_ROTATING_ZERO_RESTART},
+        {"raid6_nr",      "raid6 (N restart)",                      2, 4, 6,  ALGORITHM_ROTATING_N_RESTART},
+        {"raid6_nc",      "raid6 (N continue)",                     2, 4, 6,  ALGORITHM_ROTATING_N_CONTINUE},
+        {"raid6_n_6",     "raid6 (dedicated parity/Q n/6)",         2, 4, 6,  ALGORITHM_PARITY_N_6},
+        {"raid6_ls_6",    "raid6 (left symmetric dedicated Q 6)",   2, 4, 6,  ALGORITHM_LEFT_SYMMETRIC_6},
+        {"raid6_rs_6",    "raid6 (right symmetric dedicated Q 6)",  2, 4, 6,  ALGORITHM_RIGHT_SYMMETRIC_6},
+        {"raid6_la_6",    "raid6 (left asymmetric dedicated Q 6)",  2, 4, 6,  ALGORITHM_LEFT_ASYMMETRIC_6},
+        {"raid6_ra_6",    "raid6 (right asymmetric dedicated Q 6)", 2, 4, 6,  ALGORITHM_RIGHT_ASYMMETRIC_6}
 };
 
 /* True, if @v is in inclusive range [@min, @max] */
@@ -228,6 +260,23 @@ static const char *_argname_by_flag(const uint32_t flag)
 }
 
 /*
+ * bool helpers to test for various raid levels of a raid set,
+ * is. it's level as reported by the superblock rather than
+ * the requested raid_type passed to the constructor.
+ */
+/* Return true, if raid set in @rs is raid0 */
+static bool rs_is_raid0(struct raid_set *rs)
+{
+        return !rs->md.level;
+}
+
+/* Return true, if raid set in @rs is raid10 */
+static bool rs_is_raid10(struct raid_set *rs)
+{
+        return rs->md.level == 10;
+}
+
+/*
  * bool helpers to test for various raid levels of a raid type
  */
 
@@ -314,57 +363,184 @@ static int rs_check_for_invalid_flags(struct raid_set *rs)
         return 0;
 }
 
-static char *raid10_md_layout_to_format(int layout)
+
+/* MD raid10 bit definitions and helpers */
+#define RAID10_OFFSET                   (1 << 16) /* stripes with data copies area adjacent on devices */
+#define RAID10_BROCKEN_USE_FAR_SETS     (1 << 17) /* Broken in raid10.c: use sets instead of whole stripe rotation */
+#define RAID10_USE_FAR_SETS             (1 << 18) /* Use sets instead of whole stripe rotation */
+#define RAID10_FAR_COPIES_SHIFT         8         /* raid10 # far copies shift (2nd byte of layout) */
+
+/* Return md raid10 near copies for @layout */
+static unsigned int _raid10_near_copies(int layout)
+{
+        return layout & 0xFF;
+}
+
+/* Return md raid10 far copies for @layout */
+static unsigned int _raid10_far_copies(int layout)
+{
+        return _raid10_near_copies(layout >> RAID10_FAR_COPIES_SHIFT);
+}
+
+/* Return true if md raid10 offset for @layout */
+static unsigned int _is_raid10_offset(int layout)
+{
+        return layout & RAID10_OFFSET;
+}
+
+/* Return true if md raid10 near for @layout */
+static unsigned int _is_raid10_near(int layout)
+{
+        return !_is_raid10_offset(layout) && _raid10_near_copies(layout) > 1;
+}
+
+/* Return true if md raid10 far for @layout */
+static unsigned int _is_raid10_far(int layout)
+{
+        return !_is_raid10_offset(layout) && _raid10_far_copies(layout) > 1;
+}
+
+/* Return md raid10 layout string for @layout */
+static const char *raid10_md_layout_to_format(int layout)
 {
         /*
-         * Bit 16 and 17 stand for "offset" and "use_far_sets"
+         * Bit 16 stands for "offset"
+         * (i.e. adjacent stripes hold copies)
+         *
          * Refer to MD's raid10.c for details
          */
-        if ((layout & 0x10000) && (layout & 0x20000))
+        if (_is_raid10_offset(layout))
                 return "offset";
 
-        if ((layout & 0xFF) > 1)
+        if (_raid10_near_copies(layout) > 1)
                 return "near";
 
+        WARN_ON(_raid10_far_copies(layout) < 2);
+
         return "far";
 }
 
-static unsigned raid10_md_layout_to_copies(int layout)
+/* Return md raid10 algorithm for @name */
+static const int raid10_name_to_format(const char *name)
+{
+        if (!strcasecmp(name, "near"))
+                return ALGORITHM_RAID10_NEAR;
+        else if (!strcasecmp(name, "offset"))
+                return ALGORITHM_RAID10_OFFSET;
+        else if (!strcasecmp(name, "far"))
+                return ALGORITHM_RAID10_FAR;
+
+        return -EINVAL;
+}
+
+
+/* Return md raid10 copies for @layout */
+static unsigned int raid10_md_layout_to_copies(int layout)
 {
-        if ((layout & 0xFF) > 1)
-                return layout & 0xFF;
-        return (layout >> 8) & 0xFF;
+        return _raid10_near_copies(layout) > 1 ?
+               _raid10_near_copies(layout) : _raid10_far_copies(layout);
 }
 
-static int raid10_format_to_md_layout(char *format, unsigned copies)
+/* Return md raid10 format id for @format string */
+static int raid10_format_to_md_layout(struct raid_set *rs,
+                                      unsigned int algorithm,
+                                      unsigned int copies)
 {
-        unsigned n = 1, f = 1;
+        unsigned int n = 1, f = 1, r = 0;
 
-        if (!strcasecmp("near", format))
+        /*
+         * MD resilienece flaw:
+         *
+         * enabling use_far_sets for far/offset formats causes copies
+         * to be colocated on the same devs together with their origins!
+         *
+         * -> disable it for now in the definition above
+         */
+        if (algorithm == ALGORITHM_RAID10_DEFAULT ||
+            algorithm == ALGORITHM_RAID10_NEAR)
                 n = copies;
-        else
+
+        else if (algorithm == ALGORITHM_RAID10_OFFSET) {
+                f = copies;
+                r = RAID10_OFFSET;
+                if (!_test_flag(CTR_FLAG_RAID10_USE_NEAR_SETS, rs->ctr_flags))
+                        r |= RAID10_USE_FAR_SETS;
+
+        } else if (algorithm == ALGORITHM_RAID10_FAR) {
                 f = copies;
+                r = !RAID10_OFFSET;
+                if (!_test_flag(CTR_FLAG_RAID10_USE_NEAR_SETS, rs->ctr_flags))
+                        r |= RAID10_USE_FAR_SETS;
 
-        if (!strcasecmp("offset", format))
-                return 0x30000 | (f << 8) | n;
+        } else
+                return -EINVAL;
+
+        return r | (f << RAID10_FAR_COPIES_SHIFT) | n;
+}
+/* END: MD raid10 bit definitions and helpers */
 
-        if (!strcasecmp("far", format))
-                return 0x20000 | (f << 8) | n;
+/* Check for any of the raid10 algorithms */
+static int _got_raid10(struct raid_type *rtp, const int layout)
+{
+        if (rtp->level == 10) {
+                switch (rtp->algorithm) {
+                case ALGORITHM_RAID10_DEFAULT:
+                case ALGORITHM_RAID10_NEAR:
+                        return _is_raid10_near(layout);
+                case ALGORITHM_RAID10_OFFSET:
+                        return _is_raid10_offset(layout);
+                case ALGORITHM_RAID10_FAR:
+                        return _is_raid10_far(layout);
+                default:
+                        break;
+                }
+        }
 
-        return (f << 8) | n;
+        return 0;
 }
 
+/* Return raid_type for @name */
 static struct raid_type *get_raid_type(const char *name)
 {
-        int i;
+        struct raid_type *rtp = raid_types + ARRAY_SIZE(raid_types);
+
+        while (rtp-- > raid_types)
+                if (!strcasecmp(rtp->name, name))
+                        return rtp;
+
+        return NULL;
+}
 
-        for (i = 0; i < ARRAY_SIZE(raid_types); i++)
-                if (!strcmp(raid_types[i].name, name))
-                        return &raid_types[i];
+/* Return raid_type for @name based derived from @level and @layout */
+static struct raid_type *get_raid_type_by_ll(const int level, const int layout)
+{
+        struct raid_type *rtp = raid_types + ARRAY_SIZE(raid_types);
+
+        while (rtp-- > raid_types) {
+                /* RAID10 special checks based on @layout flags/properties */
+                if (rtp->level == level &&
+                    (_got_raid10(rtp, layout) || rtp->algorithm == layout))
+                        return rtp;
+        }
 
         return NULL;
 }
 
+/*
+ * Set the mddev properties in @rs to the new
+ * ones requested by the ctr
+ */
+static void rs_set_new(struct raid_set *rs)
+{
+        struct mddev *mddev = &rs->md;
+
+        mddev->level = mddev->new_level;
+        mddev->layout = mddev->new_layout;
+        mddev->chunk_sectors = mddev->new_chunk_sectors;
+        mddev->delta_disks = 0;
+}
+
+
 static struct raid_set *context_alloc(struct dm_target *ti, struct raid_type *raid_type, unsigned raid_devs)
 {
         unsigned i;
@@ -379,6 +555,9 @@ static struct raid_set *context_alloc(struct dm_target *ti, struct raid_type *ra
 
         mddev_init(&rs->md);
 
+        rs->raid_disks = raid_devs;
+        rs->delta_disks = 0;
+
         rs->ti = ti;
         rs->raid_type = raid_type;
         rs->md.raid_disks = raid_devs;
@@ -710,7 +889,7 @@ too_many:
 static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                              unsigned num_raid_params)
 {
-        char *raid10_format = "near";
+        int raid10_format = ALGORITHM_RAID10_DEFAULT;
         unsigned raid10_copies = 2;
         unsigned i;
         unsigned value, region_size = 0;
@@ -718,6 +897,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
         sector_t max_io_len;
         const char *arg, *key;
         struct raid_dev *rd;
+        struct raid_type *rt = rs->raid_type;
 
         arg = dm_shift_arg(as);
         num_raid_params--; /* Account for chunk_size argument */
@@ -729,7 +909,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
          * First, parse the in-order required arguments
          * "chunk_size" is the only argument of this type.
          */
-        if (rt_is_raid1(rs->raid_type)) {
+        if (rt_is_raid1(rt)) {
                 if (value)
                         DMERR("Ignoring chunk size parameter for RAID 1");
                 value = 0;
@@ -794,14 +974,11 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                 if (!strcasecmp(key, _argname_by_flag(CTR_FLAG_RAID10_FORMAT))) {
                         if (_test_and_set_flag(CTR_FLAG_RAID10_FORMAT, &rs->ctr_flags))
                                 return ti_error_einval(rs->ti, "Only one raid10_format argument pair allowed");
-                        if (!rt_is_raid10(rs->raid_type))
+                        if (!rt_is_raid10(rt))
                                 return ti_error_einval(rs->ti, "'raid10_format' is an invalid parameter for this RAID type");
-                        if (strcmp("near", arg) &&
-                            strcmp("far", arg) &&
-                            strcmp("offset", arg))
-                                return ti_error_einval(rs->ti, "Invalid 'raid10_format' value given");
-
-                        raid10_format = (char *) arg;
+                        raid10_format = raid10_name_to_format(arg);
+                        if (raid10_format < 0)
+                                return ti_error_ret(rs->ti, "Invalid 'raid10_format' value given", raid10_format);
                         continue;
                 }
 
@@ -823,7 +1000,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                         rd->rdev.recovery_offset = 0;
                         _set_flag(CTR_FLAG_REBUILD, &rs->ctr_flags);
                 } else if (!strcasecmp(key, _argname_by_flag(CTR_FLAG_WRITE_MOSTLY))) {
-                        if (!rt_is_raid1(rs->raid_type))
+                        if (!rt_is_raid1(rt))
                                 return ti_error_einval(rs->ti, "write_mostly option is only valid for RAID1");
 
                         if (!_in_range(value, 0, rs->md.raid_disks - 1))
@@ -832,7 +1009,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                         set_bit(WriteMostly, &rs->dev[value].rdev.flags);
                         _set_flag(CTR_FLAG_WRITE_MOSTLY, &rs->ctr_flags);
                 } else if (!strcasecmp(key, _argname_by_flag(CTR_FLAG_MAX_WRITE_BEHIND))) {
-                        if (!rt_is_raid1(rs->raid_type))
+                        if (!rt_is_raid1(rt))
                                 return ti_error_einval(rs->ti, "max_write_behind option is only valid for RAID1");
 
                         if (_test_and_set_flag(CTR_FLAG_MAX_WRITE_BEHIND, &rs->ctr_flags))
@@ -862,7 +1039,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                          */
                         value /= 2;
 
-                        if (!rt_is_raid456(rs->raid_type))
+                        if (!rt_is_raid456(rt))
                                 return ti_error_einval(rs->ti, "Inappropriate argument: stripe_cache");
                         if (raid5_set_cache_size(&rs->md, (int)value))
                                 return ti_error_einval(rs->ti, "Bad stripe_cache size");
@@ -909,29 +1086,35 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
         if (dm_set_target_max_io_len(rs->ti, max_io_len))
                 return -EINVAL;
 
-        if (rt_is_raid10(rs->raid_type)) {
+        if (rt_is_raid10(rt)) {
                 if (raid10_copies > rs->md.raid_disks)
                         return ti_error_einval(rs->ti, "Not enough devices to satisfy specification");
 
-                /*
-                 * If the format is not "near", we only support
-                 * two copies at the moment.
-                 */
-                if (strcmp("near", raid10_format) && (raid10_copies > 2))
-                        return ti_error_einval(rs->ti, "Too many copies for given RAID10 format.");
+                rs->md.new_layout = raid10_format_to_md_layout(rs, raid10_format, raid10_copies);
+                if (rs->md.new_layout < 0)
+                        return ti_error_ret(rs->ti, "Error getting raid10 format", rs->md.new_layout);
+
+                rt = get_raid_type_by_ll(10, rs->md.new_layout);
+                if (!rt)
+                        return ti_error_einval(rs->ti, "Failed to recognize new raid10 layout");
+
+                if ((rt->algorithm == ALGORITHM_RAID10_DEFAULT ||
+                     rt->algorithm == ALGORITHM_RAID10_NEAR) &&
+                    _test_flag(CTR_FLAG_RAID10_USE_NEAR_SETS, rs->ctr_flags))
+                        return ti_error_einval(rs->ti, "RAID10 format \"near\" and \"raid10_use_near_sets\" are incompatible");
 
                 /* (Len * #mirrors) / #devices */
                 sectors_per_dev = rs->ti->len * raid10_copies;
                 sector_div(sectors_per_dev, rs->md.raid_disks);
 
-                rs->md.layout = raid10_format_to_md_layout(raid10_format,
-                                                           raid10_copies);
+                rs->md.layout = raid10_format_to_md_layout(rs, raid10_format, raid10_copies);
                 rs->md.new_layout = rs->md.layout;
-        } else if (!rt_is_raid1(rs->raid_type) &&
+        } else if (!rt_is_raid1(rt) &&
                    sector_div(sectors_per_dev,
-                              (rs->md.raid_disks - rs->raid_type->parity_devs)))
+                              (rs->md.raid_disks - rt->parity_devs)))
                 return ti_error_einval(rs->ti, "Target length not divisible by number of data devices");
 
+        rs->raid10_copies = raid10_copies;
         rs->md.dev_sectors = sectors_per_dev;
 
         /* Assume there are no metadata devices until the drives are parsed */
@@ -956,6 +1139,13 @@ static int raid_is_congested(struct dm_target_callbacks *cb, int bits)
         return mddev_congested(&rs->md, bits);
 }
 
+/*  Features */
+#define FEATURE_FLAG_SUPPORTS_RESHAPE   0x1
+
+/* State flags for sb->flags */
+#define SB_FLAG_RESHAPE_ACTIVE          0x1
+#define SB_FLAG_RESHAPE_BACKWARDS       0x2
+
 /*
  * This structure is never routinely used by userspace, unlike md superblocks.
  * Devices with this superblock should only ever be accessed via device-mapper.
@@ -963,13 +1153,14 @@ static int raid_is_congested(struct dm_target_callbacks *cb, int bits)
 #define DM_RAID_MAGIC 0x64526D44
 struct dm_raid_superblock {
         __le32 magic;           /* "DmRd" */
-        __le32 features;        /* Used to indicate possible future changes */
+        __le32 compat_features; /* Used to indicate compatible features (like 1.8.0 ondisk metadata extension) */
 
-        __le32 num_devices;     /* Number of devices in this array. (Max 64) */
-        __le32 array_position;  /* The position of this drive in the array */
+        __le32 num_devices;     /* Number of devices in this raid set. (Max 64) */
+        __le32 array_position;  /* The position of this drive in the raid set */
 
         __le64 events;          /* Incremented by md when superblock updated */
-        __le64 failed_devices;  /* Bit field of devices to indicate failures */
+        __le64 failed_devices;  /* Pre 1.8.0 part of bit field of devices to */
+                                /* indicate failures (see extension below) */
 
         /*
          * This offset tracks the progress of the repair or replacement of
@@ -978,19 +1169,62 @@ struct dm_raid_superblock {
         __le64 disk_recovery_offset;
 
         /*
-         * This offset tracks the progress of the initial array
+         * This offset tracks the progress of the initial raid set
          * synchronisation/parity calculation.
          */
         __le64 array_resync_offset;
 
         /*
-         * RAID characteristics
+         * raid characteristics
          */
         __le32 level;
         __le32 layout;
         __le32 stripe_sectors;
 
-        /* Remainder of a logical block is zero-filled when writing (see super_sync()). */
+        /********************************************************************
+         * BELOW FOLLOW V1.8.0 EXTENSIONS TO THE PRISTINE SUPERBLOCK FORMAT!!!
+         *
+         * FEATURE_FLAG_SUPPORTS_RESHAPE in the features member indicates that those exist
+         */
+
+        __le32 flags; /* Flags defining array states for reshaping */
+
+        /*
+         * This offset tracks the progress of a raid
+         * set reshape in order to be able to restart it
+         */
+        __le64 reshape_position;
+
+        /*
+         * These define the properties of the array in case of an interrupted reshape
+         */
+        __le32 new_level;
+        __le32 new_layout;
+        __le32 new_stripe_sectors;
+        __le32 delta_disks;
+
+        __le64 array_sectors; /* Array size in sectors */
+
+        /*
+         * Sector offsets to data on devices (reshaping).
+         * Needed to support out of place reshaping, thus
+         * not writing over any stripes whilst converting
+         * them from old to new layout
+         */
+        __le64 data_offset;
+        __le64 new_data_offset;
+
+        __le64 sectors; /* Used device size in sectors */
+
+        /*
+         * Additonal Bit field of devices indicating failures to support
+         * up to 256 devices with the 1.8.0 on-disk metadata format
+         */
+        __le64 extended_failed_devices[DISKS_ARRAY_ELEMS - 1];
+
+        __le32 incompat_features;       /* Used to indicate any incompatible features */
+
+        /* Always set rest up to logical block size to 0 when writing (see get_metadata_device() below). */
 } __packed;
 
 static int read_disk_sb(struct md_rdev *rdev, int size)
@@ -1012,6 +1246,19 @@ static int read_disk_sb(struct md_rdev *rdev, int size)
         return 0;
 }
 
+static void sb_retrieve_failed_devices(struct dm_raid_superblock *sb, uint64_t *failed_devices)
+{
+        failed_devices[0] = le64_to_cpu(sb->failed_devices);
+        memset(failed_devices + 1, 0, sizeof(sb->extended_failed_devices));
+
+        if (_test_flag(FEATURE_FLAG_SUPPORTS_RESHAPE, le32_to_cpu(sb->compat_features))) {
+                int i = ARRAY_SIZE(sb->extended_failed_devices);
+
+                while (i--)
+                        failed_devices[i+1] = le64_to_cpu(sb->extended_failed_devices[i]);
+        }
+}
+
 static void super_sync(struct mddev *mddev, struct md_rdev *rdev)
 {
         int i;
@@ -1030,7 +1277,7 @@ static void super_sync(struct mddev *mddev, struct md_rdev *rdev)
         memset(sb + 1, 0, rdev->sb_size - sizeof(*sb));
 
         sb->magic = cpu_to_le32(DM_RAID_MAGIC);
-        sb->features = cpu_to_le32(0);  /* No features yet */
+        sb->compat_features = cpu_to_le32(0);   /* No features yet */
 
         sb->num_devices = cpu_to_le32(mddev->raid_disks);
         sb->array_position = cpu_to_le32(rdev->raid_disk);
@@ -1103,119 +1350,196 @@ static int super_load(struct md_rdev *rdev, struct md_rdev *refdev)
         return (events_sb > events_refsb) ? 1 : 0;
 }
 
-static int super_init_validation(struct mddev *mddev, struct md_rdev *rdev)
+static int super_init_validation(struct raid_set *rs, struct md_rdev *rdev)
 {
         int role;
-        struct raid_set *rs = container_of(mddev, struct raid_set, md);
+        unsigned int d;
+        struct mddev *mddev = &rs->md;
         uint64_t events_sb;
-        uint64_t failed_devices;
+        uint64_t failed_devices[DISKS_ARRAY_ELEMS];
         struct dm_raid_superblock *sb;
-        uint32_t new_devs = 0;
-        uint32_t rebuilds = 0;
+        uint32_t new_devs = 0, rebuild_and_new = 0, rebuilds = 0;
         struct md_rdev *r;
         struct dm_raid_superblock *sb2;
 
         sb = page_address(rdev->sb_page);
         events_sb = le64_to_cpu(sb->events);
-        failed_devices = le64_to_cpu(sb->failed_devices);
 
         /*
          * Initialise to 1 if this is a new superblock.
          */
         mddev->events = events_sb ? : 1;
 
+        mddev->reshape_position = MaxSector;
+
         /*
-         * Reshaping is not currently allowed
+         * Reshaping is supported, e.g. reshape_position is valid
+         * in superblock and superblock content is authoritative.
          */
-        if (le32_to_cpu(sb->level) != mddev->level) {
-                DMERR("Reshaping arrays not yet supported. (RAID level change)");
-                return -EINVAL;
-        }
-        if (le32_to_cpu(sb->layout) != mddev->layout) {
-                DMERR("Reshaping arrays not yet supported. (RAID layout change)");
-                DMERR("  0x%X vs 0x%X", le32_to_cpu(sb->layout), mddev->layout);
-                DMERR("  Old layout: %s w/ %d copies",
-                      raid10_md_layout_to_format(le32_to_cpu(sb->layout)),
-                      raid10_md_layout_to_copies(le32_to_cpu(sb->layout)));
-                DMERR("  New layout: %s w/ %d copies",
-                      raid10_md_layout_to_format(mddev->layout),
-                      raid10_md_layout_to_copies(mddev->layout));
-                return -EINVAL;
-        }
-        if (le32_to_cpu(sb->stripe_sectors) != mddev->chunk_sectors) {
-                DMERR("Reshaping arrays not yet supported. (stripe sectors change)");
-                return -EINVAL;
-        }
+        if (_test_flag(FEATURE_FLAG_SUPPORTS_RESHAPE, le32_to_cpu(sb->compat_features))) {
+                /* Superblock is authoritative wrt given raid set layout! */
+                mddev->raid_disks = le32_to_cpu(sb->num_devices);
+                mddev->level = le32_to_cpu(sb->level);
+                mddev->layout = le32_to_cpu(sb->layout);
+                mddev->chunk_sectors = le32_to_cpu(sb->stripe_sectors);
+                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_stripe_sectors);
+                mddev->delta_disks = le32_to_cpu(sb->delta_disks);
+                mddev->array_sectors = le64_to_cpu(sb->array_sectors);
+
+                /* raid was reshaping and got interrupted */
+                if (_test_flag(SB_FLAG_RESHAPE_ACTIVE, le32_to_cpu(sb->flags))) {
+                        if (_test_flag(CTR_FLAG_DELTA_DISKS, rs->ctr_flags)) {
+                                DMERR("Reshape requested but raid set is still reshaping");
+                                return -EINVAL;
+                        }
 
-        /* We can only change the number of devices in RAID1 right now */
-        if (!rt_is_raid1(rs->raid_type) &&
-            (le32_to_cpu(sb->num_devices) != mddev->raid_disks)) {
-                DMERR("Reshaping arrays not yet supported. (device count change)");
-                return -EINVAL;
+                        if (mddev->delta_disks < 0 ||
+                            (!mddev->delta_disks && _test_flag(SB_FLAG_RESHAPE_BACKWARDS, le32_to_cpu(sb->flags))))
+                                mddev->reshape_backwards = 1;
+                        else
+                                mddev->reshape_backwards = 0;
+
+                        mddev->reshape_position = le64_to_cpu(sb->reshape_position);
+                        rs->raid_type = get_raid_type_by_ll(mddev->level, mddev->layout);
+                }
+
+        } else {
+                /*
+                 * Reshaping is not allowed, because we don't have the appropriate metadata
+                 */
+                if (le32_to_cpu(sb->level) != mddev->level) {
+                        DMERR("Reshaping/takeover raid sets not yet supported. (raid level/stripes/size change)");
+                        return -EINVAL;
+                }
+                if (le32_to_cpu(sb->layout) != mddev->layout) {
+                        DMERR("Reshaping raid sets not yet supported. (raid layout change)");
+                        DMERR("  0x%X vs 0x%X", le32_to_cpu(sb->layout), mddev->layout);
+                        DMERR("  Old layout: %s w/ %d copies",
+                              raid10_md_layout_to_format(le32_to_cpu(sb->layout)),
+                              raid10_md_layout_to_copies(le32_to_cpu(sb->layout)));
+                        DMERR("  New layout: %s w/ %d copies",
+                              raid10_md_layout_to_format(mddev->layout),
+                              raid10_md_layout_to_copies(mddev->layout));
+                        return -EINVAL;
+                }
+                if (le32_to_cpu(sb->stripe_sectors) != mddev->chunk_sectors) {
+                        DMERR("Reshaping raid sets not yet supported. (stripe sectors change)");
+                        return -EINVAL;
+                }
+
+                /* We can only change the number of devices in raid1 with old (i.e. pre 1.0.7) metadata */
+                if (!rt_is_raid1(rs->raid_type) &&
+                    (le32_to_cpu(sb->num_devices) != mddev->raid_disks)) {
+                        DMERR("Reshaping raid sets not yet supported. (device count change from %u to %u)",
+                              sb->num_devices, mddev->raid_disks);
+                        return -EINVAL;
+                }
+
+                /* Table line is checked vs. authoritative superblock */
+                rs_set_new(rs);
         }
 
-        if (!(_test_flags(CTR_FLAGS_ANY_SYNC, rs->ctr_flags)))
+        if (!_test_flag(CTR_FLAG_NOSYNC, rs->ctr_flags))
                 mddev->recovery_cp = le64_to_cpu(sb->array_resync_offset);
 
         /*
          * During load, we set FirstUse if a new superblock was written.
          * There are two reasons we might not have a superblock:
-         * 1) The array is brand new - in which case, all of the
+         * 1) The raid set is brand new - in which case, all of the
          *    devices must have their In_sync bit set.  Also,
          *    recovery_cp must be 0, unless forced.
-         * 2) This is a new device being added to an old array
+         * 2) This is a new device being added to an old raid set
          *    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.
          */
+        d = 0;
         rdev_for_each(r, mddev) {
+                if (test_bit(FirstUse, &r->flags))
+                        new_devs++;
+
                 if (!test_bit(In_sync, &r->flags)) {
-                        DMINFO("Device %d specified for rebuild: "
-                               "Clearing superblock", r->raid_disk);
+                        DMINFO("Device %d specified for rebuild; clearing superblock",
+                                r->raid_disk);
                         rebuilds++;
-                } else if (test_bit(FirstUse, &r->flags))
-                        new_devs++;
+
+                        if (test_bit(FirstUse, &r->flags))
+                                rebuild_and_new++;
+                }
+
+                d++;
         }
 
-        if (!rebuilds) {
-                if (new_devs == mddev->raid_disks) {
-                        DMINFO("Superblocks created for new array");
+        if (new_devs == rs->raid_disks || !rebuilds) {
+                /* Replace a broken device */
+                if (new_devs == 1 && !rs->delta_disks)
+                        ;
+                if (new_devs == rs->raid_disks) {
+                        DMINFO("Superblocks created for new raid set");
                         set_bit(MD_ARRAY_FIRST_USE, &mddev->flags);
-                } else if (new_devs) {
-                        DMERR("New device injected "
-                              "into existing array without 'rebuild' "
-                              "parameter specified");
+                        mddev->recovery_cp = 0;
+                } else if (new_devs && new_devs != rs->raid_disks && !rebuilds) {
+                        DMERR("New device injected into existing raid set without "
+                              "'delta_disks' or 'rebuild' parameter specified");
                         return -EINVAL;
                 }
-        } else if (new_devs) {
-                DMERR("'rebuild' devices cannot be "
-                      "injected into an array with other first-time devices");
-                return -EINVAL;
-        } else if (mddev->recovery_cp != MaxSector) {
-                DMERR("'rebuild' specified while array is not in-sync");
+        } else if (new_devs && new_devs != rebuilds) {
+                DMERR("%u 'rebuild' devices cannot be injected into"
+                      " a raid set with %u other first-time devices",
+                      rebuilds, new_devs);
                 return -EINVAL;
+        } else if (rebuilds) {
+                if (rebuild_and_new && rebuilds != rebuild_and_new) {
+                        DMERR("new device%s provided without 'rebuild'",
+                              new_devs > 1 ? "s" : "");
+                        return -EINVAL;
+                } else if (mddev->recovery_cp != MaxSector) {
+                        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");
+                        return -EINVAL;
+                }
         }
 
         /*
          * Now we set the Faulty bit for those devices that are
          * recorded in the superblock as failed.
          */
+        sb_retrieve_failed_devices(sb, failed_devices);
         rdev_for_each(r, mddev) {
                 if (!r->sb_page)
                         continue;
                 sb2 = page_address(r->sb_page);
                 sb2->failed_devices = 0;
+                memset(sb2->extended_failed_devices, 0, sizeof(sb2->extended_failed_devices));
 
                 /*
                  * Check for any device re-ordering.
                  */
                 if (!test_bit(FirstUse, &r->flags) && (r->raid_disk >= 0)) {
                         role = le32_to_cpu(sb2->array_position);
+                        if (role < 0)
+                                continue;
+
                         if (role != r->raid_disk) {
-                                if (!rt_is_raid1(rs->raid_type))
-                                        return ti_error_einval(rs->ti, "Cannot change device "
-                                                                       "positions in RAID array");
-                                DMINFO("RAID1 device #%d now at position #%d",
+                                if (_is_raid10_near(mddev->layout)) {
+                                        if (mddev->raid_disks % _raid10_near_copies(mddev->layout) ||
+                                            rs->raid_disks % rs->raid10_copies)
+                                                return ti_error_einval(rs->ti, "Cannot change raid10 near "
+                                                                               "set to odd # of devices!");
+
+                                        sb2->array_position = cpu_to_le32(r->raid_disk);
+
+                                } else if (!(rs_is_raid10(rs) && rt_is_raid0(rs->raid_type)) &&
+                                    !(rs_is_raid0(rs) && rt_is_raid10(rs->raid_type)) &&
+                                    !rt_is_raid1(rs->raid_type))
+                                        return ti_error_einval(rs->ti, "Cannot change device positions in raid set");
+
+                                DMINFO("raid device #%d now at position #%d",
                                        role, r->raid_disk);
                         }
 
@@ -1223,7 +1547,7 @@ static int super_init_validation(struct mddev *mddev, struct md_rdev *rdev)
                          * Partial recovery is performed on
                          * returning failed devices.
                          */
-                        if (failed_devices & (1 << role))
+                        if (test_bit(role, (void *) failed_devices))
                                 set_bit(Faulty, &r->flags);
                 }
         }
@@ -1234,16 +1558,21 @@ static int super_init_validation(struct mddev *mddev, struct md_rdev *rdev)
 static int super_validate(struct raid_set *rs, struct md_rdev *rdev)
 {
         struct mddev *mddev = &rs->md;
-        struct dm_raid_superblock *sb = page_address(rdev->sb_page);
+        struct dm_raid_superblock *sb;
+
+        if (!rdev->sb_page)
+                return 0;
+
+        sb = page_address(rdev->sb_page);
 
         /*
          * If mddev->events is not set, we know we have not yet initialized
          * the array.
          */
-        if (!mddev->events && super_init_validation(mddev, rdev))
+        if (!mddev->events && super_init_validation(rs, rdev))
                 return -EINVAL;
 
-        if (le32_to_cpu(sb->features)) {
+        if (sb->compat_features || sb->incompat_features) {
                 rs->ti->error = "Unable to assemble array: No feature flags supported yet";
                 return -EINVAL;
         }
@@ -1252,23 +1581,32 @@ static int super_validate(struct raid_set *rs, struct md_rdev *rdev)
         mddev->bitmap_info.offset = rt_is_raid0(rs->raid_type) ? 0 : to_sector(4096);
         rdev->mddev->bitmap_info.default_offset = mddev->bitmap_info.offset;
 
-        if (!test_bit(FirstUse, &rdev->flags)) {
+        if (!test_and_clear_bit(FirstUse, &rdev->flags)) {
+                /* Retrieve device size stored in superblock to be prepared for shrink */
+                rdev->sectors = le64_to_cpu(sb->sectors);
                 rdev->recovery_offset = le64_to_cpu(sb->disk_recovery_offset);
-                if (rdev->recovery_offset != MaxSector)
-                        clear_bit(In_sync, &rdev->flags);
+                if (rdev->recovery_offset == MaxSector)
+                        set_bit(In_sync, &rdev->flags);
+                /*
+                 * 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)
+                        clear_bit(In_sync, &rdev->flags); /* Mandatory for recovery */
         }
 
         /*
          * If a device comes back, set it as not In_sync and no longer faulty.
          */
-        if (test_bit(Faulty, &rdev->flags)) {
-                clear_bit(Faulty, &rdev->flags);
+        if (test_and_clear_bit(Faulty, &rdev->flags)) {
+                rdev->recovery_offset = 0;
                 clear_bit(In_sync, &rdev->flags);
                 rdev->saved_raid_disk = rdev->raid_disk;
-                rdev->recovery_offset = 0;
         }
 
-        clear_bit(FirstUse, &rdev->flags);
+        /* Reshape support -> restore repective data offsets */
+        rdev->data_offset = le64_to_cpu(sb->data_offset);
+        rdev->new_data_offset = le64_to_cpu(sb->new_data_offset);
 
         return 0;
 }