md: add possibility to change data-offset for devices.

When reshaping we can avoid costly intermediate backup by
changing the 'start' address of the array on the device
(if there is enough room).

So as a first step, allow such a change to be requested
through sysfs, and recorded in v1.x metadata.

(As we didn't previous check that all 'pad' fields were zero,
 we need a new FEATURE flag for this.
 A (belatedly) check that all remaining 'pad' fields are
 zero to avoid a repeat of this)

The new data offset must be requested separately for each device.
This allows each to have a different change in the data offset.
This is not likely to be used often but as data_offset can be
set per-device, new_data_offset should be too.

This patch also removes the 'acknowledged' arg to rdev_set_badblocks as
it is never used and never will be.  At the same time we add a new
arg ('in_new') which is currently always zero but will be used more
soon.

When a reshape finishes we will need to update the data_offset
and rdev->sectors.  So provide an exported function to do that.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 196 insertions, 21 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 44bb1d52dd4c..9fa98fc74b05 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1035,12 +1035,17 @@ static unsigned int calc_sb_csum(mdp_super_t * sb)
 struct super_type  {
         char                *name;
         struct module       *owner;
-        int                 (*load_super)(struct md_rdev *rdev, struct md_rdev *refdev,
+        int                 (*load_super)(struct md_rdev *rdev,
+                                          struct md_rdev *refdev,
                                           int minor_version);
-        int                 (*validate_super)(struct mddev *mddev, struct md_rdev *rdev);
-        void                (*sync_super)(struct mddev *mddev, struct md_rdev *rdev);
+        int                 (*validate_super)(struct mddev *mddev,
+                                              struct md_rdev *rdev);
+        void                (*sync_super)(struct mddev *mddev,
+                                          struct md_rdev *rdev);
         unsigned long long  (*rdev_size_change)(struct md_rdev *rdev,
                                                 sector_t num_sectors);
+        int                 (*allow_new_offset)(struct md_rdev *rdev,
+                                                unsigned long long new_offset);
 };
 
 /*
@@ -1112,6 +1117,7 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
 
         rdev->preferred_minor = sb->md_minor;
         rdev->data_offset = 0;
+        rdev->new_data_offset = 0;
         rdev->sb_size = MD_SB_BYTES;
         rdev->badblocks.shift = -1;
 
@@ -1438,6 +1444,12 @@ super_90_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
         return num_sectors;
 }
 
+static int
+super_90_allow_new_offset(struct md_rdev *rdev, unsigned long long new_offset)
+{
+        /* non-zero offset changes not possible with v0.90 */
+        return new_offset == 0;
+}
 
 /*
  * version 1 superblock
@@ -1473,6 +1485,7 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
         struct mdp_superblock_1 *sb;
         int ret;
         sector_t sb_start;
+        sector_t sectors;
         char b[BDEVNAME_SIZE], b2[BDEVNAME_SIZE];
         int bmask;
 
@@ -1527,9 +1540,18 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
                        bdevname(rdev->bdev,b));
                 return -EINVAL;
         }
+        if (sb->pad0 ||
+            sb->pad3[0] ||
+            memcmp(sb->pad3, sb->pad3+1, sizeof(sb->pad3) - sizeof(sb->pad3[1])))
+                /* Some padding is non-zero, might be a new feature */
+                return -EINVAL;
 
         rdev->preferred_minor = 0xffff;
         rdev->data_offset = le64_to_cpu(sb->data_offset);
+        rdev->new_data_offset = rdev->data_offset;
+        if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_RESHAPE_ACTIVE) &&
+            (le32_to_cpu(sb->feature_map) & MD_FEATURE_NEW_OFFSET))
+                rdev->new_data_offset += (s32)le32_to_cpu(sb->new_offset);
         atomic_set(&rdev->corrected_errors, le32_to_cpu(sb->cnt_corrected_read));
 
         rdev->sb_size = le32_to_cpu(sb->max_dev) * 2 + 256;
@@ -1540,6 +1562,9 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
         if (minor_version
             && rdev->data_offset < sb_start + (rdev->sb_size/512))
                 return -EINVAL;
+        if (minor_version
+            && rdev->new_data_offset < sb_start + (rdev->sb_size/512))
+                return -EINVAL;
 
         if (sb->level == cpu_to_le32(LEVEL_MULTIPATH))
                 rdev->desc_nr = -1;
@@ -1611,16 +1636,14 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
                 else
                         ret = 0;
         }
-        if (minor_version)
-                rdev->sectors = (i_size_read(rdev->bdev->bd_inode) >> 9) -
-                        le64_to_cpu(sb->data_offset);
-        else
-                rdev->sectors = rdev->sb_start;
-        if (rdev->sectors < le64_to_cpu(sb->data_size))
+        if (minor_version) {
+                sectors = (i_size_read(rdev->bdev->bd_inode) >> 9);
+                sectors -= rdev->data_offset;
+        } else
+                sectors = rdev->sb_start;
+        if (sectors < le64_to_cpu(sb->data_size))
                 return -EINVAL;
         rdev->sectors = le64_to_cpu(sb->data_size);
-        if (le64_to_cpu(sb->size) > rdev->sectors)
-                return -EINVAL;
         return ret;
 }
 
@@ -1745,7 +1768,6 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
         sb->feature_map = 0;
         sb->pad0 = 0;
         sb->recovery_offset = cpu_to_le64(0);
-        memset(sb->pad1, 0, sizeof(sb->pad1));
         memset(sb->pad3, 0, sizeof(sb->pad3));
 
         sb->utime = cpu_to_le64((__u64)mddev->utime);
@@ -1767,6 +1789,8 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
                 sb->devflags |= WriteMostly1;
         else
                 sb->devflags &= ~WriteMostly1;
+        sb->data_offset = cpu_to_le64(rdev->data_offset);
+        sb->data_size = cpu_to_le64(rdev->sectors);
 
         if (mddev->bitmap && mddev->bitmap_info.file == NULL) {
                 sb->bitmap_offset = cpu_to_le32((__u32)mddev->bitmap_info.offset);
@@ -1795,6 +1819,12 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
                     mddev->reshape_backwards)
                         sb->feature_map
                                 |= cpu_to_le32(MD_FEATURE_RESHAPE_BACKWARDS);
+                if (rdev->new_data_offset != rdev->data_offset) {
+                        sb->feature_map
+                                |= cpu_to_le32(MD_FEATURE_NEW_OFFSET);
+                        sb->new_offset = cpu_to_le32((__u32)(rdev->new_data_offset
+                                                             - rdev->data_offset));
+                }
         }
 
         if (rdev->badblocks.count == 0)
@@ -1871,6 +1901,8 @@ super_1_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
         sector_t max_sectors;
         if (num_sectors && num_sectors < rdev->mddev->dev_sectors)
                 return 0; /* component must fit device */
+        if (rdev->data_offset != rdev->new_data_offset)
+                return 0; /* too confusing */
         if (rdev->sb_start < rdev->data_offset) {
                 /* minor versions 1 and 2; superblock before data */
                 max_sectors = i_size_read(rdev->bdev->bd_inode) >> 9;
@@ -1898,6 +1930,40 @@ super_1_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
                        rdev->sb_page);
         md_super_wait(rdev->mddev);
         return num_sectors;
+
+}
+
+static int
+super_1_allow_new_offset(struct md_rdev *rdev,
+                         unsigned long long new_offset)
+{
+        /* All necessary checks on new >= old have been done */
+        struct bitmap *bitmap;
+        if (new_offset >= rdev->data_offset)
+                return 1;
+
+        /* with 1.0 metadata, there is no metadata to tread on
+         * so we can always move back */
+        if (rdev->mddev->minor_version == 0)
+                return 1;
+
+        /* otherwise we must be sure not to step on
+         * any metadata, so stay:
+         * 36K beyond start of superblock
+         * beyond end of badblocks
+         * beyond write-intent bitmap
+         */
+        if (rdev->sb_start + (32+4)*2 > new_offset)
+                return 0;
+        bitmap = rdev->mddev->bitmap;
+        if (bitmap && !rdev->mddev->bitmap_info.file &&
+            rdev->sb_start + rdev->mddev->bitmap_info.offset +
+            bitmap->file_pages * (PAGE_SIZE>>9) > new_offset)
+                return 0;
+        if (rdev->badblocks.sector + rdev->badblocks.size > new_offset)
+                return 0;
+
+        return 1;
 }
 
 static struct super_type super_types[] = {
@@ -1908,6 +1974,7 @@ static struct super_type super_types[] = {
                 .validate_super     = super_90_validate,
                 .sync_super         = super_90_sync,
                 .rdev_size_change   = super_90_rdev_size_change,
+                .allow_new_offset   = super_90_allow_new_offset,
         },
         [1] = {
                 .name   = "md-1",
@@ -1916,6 +1983,7 @@ static struct super_type super_types[] = {
                 .validate_super     = super_1_validate,
                 .sync_super         = super_1_sync,
                 .rdev_size_change   = super_1_rdev_size_change,
+                .allow_new_offset   = super_1_allow_new_offset,
         },
 };
 
@@ -2823,9 +2891,8 @@ offset_show(struct md_rdev *rdev, char *page)
 static ssize_t
 offset_store(struct md_rdev *rdev, const char *buf, size_t len)
 {
-        char *e;
-        unsigned long long offset = simple_strtoull(buf, &e, 10);
-        if (e==buf || (*e && *e != '\n'))
+        unsigned long long offset;
+        if (strict_strtoull(buf, 10, &offset) < 0)
                 return -EINVAL;
         if (rdev->mddev->pers && rdev->raid_disk >= 0)
                 return -EBUSY;
@@ -2840,6 +2907,63 @@ offset_store(struct md_rdev *rdev, const char *buf, size_t len)
 static struct rdev_sysfs_entry rdev_offset =
 __ATTR(offset, S_IRUGO|S_IWUSR, offset_show, offset_store);
 
+static ssize_t new_offset_show(struct md_rdev *rdev, char *page)
+{
+        return sprintf(page, "%llu\n",
+                       (unsigned long long)rdev->new_data_offset);
+}
+
+static ssize_t new_offset_store(struct md_rdev *rdev,
+                                const char *buf, size_t len)
+{
+        unsigned long long new_offset;
+        struct mddev *mddev = rdev->mddev;
+
+        if (strict_strtoull(buf, 10, &new_offset) < 0)
+                return -EINVAL;
+
+        if (mddev->sync_thread)
+                return -EBUSY;
+        if (new_offset == rdev->data_offset)
+                /* reset is always permitted */
+                ;
+        else if (new_offset > rdev->data_offset) {
+                /* must not push array size beyond rdev_sectors */
+                if (new_offset - rdev->data_offset
+                    + mddev->dev_sectors > rdev->sectors)
+                                return -E2BIG;
+        }
+        /* Metadata worries about other space details. */
+
+        /* decreasing the offset is inconsistent with a backwards
+         * reshape.
+         */
+        if (new_offset < rdev->data_offset &&
+            mddev->reshape_backwards)
+                return -EINVAL;
+        /* Increasing offset is inconsistent with forwards
+         * reshape.  reshape_direction should be set to
+         * 'backwards' first.
+         */
+        if (new_offset > rdev->data_offset &&
+            !mddev->reshape_backwards)
+                return -EINVAL;
+
+        if (mddev->pers && mddev->persistent &&
+            !super_types[mddev->major_version]
+            .allow_new_offset(rdev, new_offset))
+                return -E2BIG;
+        rdev->new_data_offset = new_offset;
+        if (new_offset > rdev->data_offset)
+                mddev->reshape_backwards = 1;
+        else if (new_offset < rdev->data_offset)
+                mddev->reshape_backwards = 0;
+
+        return len;
+}
+static struct rdev_sysfs_entry rdev_new_offset =
+__ATTR(new_offset, S_IRUGO|S_IWUSR, new_offset_show, new_offset_store);
+
 static ssize_t
 rdev_size_show(struct md_rdev *rdev, char *page)
 {
@@ -2884,6 +3008,8 @@ rdev_size_store(struct md_rdev *rdev, const char *buf, size_t len)
 
         if (strict_blocks_to_sectors(buf, &sectors) < 0)
                 return -EINVAL;
+        if (rdev->data_offset != rdev->new_data_offset)
+                return -EINVAL; /* too confusing */
         if (my_mddev->pers && rdev->raid_disk >= 0) {
                 if (my_mddev->persistent) {
                         sectors = super_types[my_mddev->major_version].
@@ -3020,6 +3146,7 @@ static struct attribute *rdev_default_attrs[] = {
         &rdev_errors.attr,
         &rdev_slot.attr,
         &rdev_offset.attr,
+        &rdev_new_offset.attr,
         &rdev_size.attr,
         &rdev_recovery_start.attr,
         &rdev_bad_blocks.attr,
@@ -3094,6 +3221,7 @@ int md_rdev_init(struct md_rdev *rdev)
         rdev->raid_disk = -1;
         rdev->flags = 0;
         rdev->data_offset = 0;
+        rdev->new_data_offset = 0;
         rdev->sb_events = 0;
         rdev->last_read_error.tv_sec  = 0;
         rdev->last_read_error.tv_nsec = 0;
@@ -3598,7 +3726,17 @@ raid_disks_store(struct mddev *mddev, const char *buf, size_t len)
         if (mddev->pers)
                 rv = update_raid_disks(mddev, n);
         else if (mddev->reshape_position != MaxSector) {
+                struct md_rdev *rdev;
                 int olddisks = mddev->raid_disks - mddev->delta_disks;
+
+                rdev_for_each(rdev, mddev) {
+                        if (olddisks < n &&
+                            rdev->data_offset < rdev->new_data_offset)
+                                return -EINVAL;
+                        if (olddisks > n &&
+                            rdev->data_offset > rdev->new_data_offset)
+                                return -EINVAL;
+                }
                 mddev->delta_disks = n - olddisks;
                 mddev->raid_disks = n;
                 mddev->reshape_backwards = (mddev->delta_disks < 0);
@@ -4445,6 +4583,7 @@ reshape_position_show(struct mddev *mddev, char *page)
 static ssize_t
 reshape_position_store(struct mddev *mddev, const char *buf, size_t len)
 {
+        struct md_rdev *rdev;
         char *e;
         unsigned long long new = simple_strtoull(buf, &e, 10);
         if (mddev->pers)
@@ -4457,6 +4596,8 @@ reshape_position_store(struct mddev *mddev, const char *buf, size_t len)
         mddev->new_level = mddev->level;
         mddev->new_layout = mddev->layout;
         mddev->new_chunk_sectors = mddev->chunk_sectors;
+        rdev_for_each(rdev, mddev)
+                rdev->new_data_offset = rdev->data_offset;
         return len;
 }
 
@@ -6001,6 +6142,7 @@ static int update_size(struct mddev *mddev, sector_t num_sectors)
 static int update_raid_disks(struct mddev *mddev, int raid_disks)
 {
         int rv;
+        struct md_rdev *rdev;
         /* change the number of raid disks */
         if (mddev->pers->check_reshape == NULL)
                 return -EINVAL;
@@ -6009,6 +6151,16 @@ static int update_raid_disks(struct mddev *mddev, int raid_disks)
                 return -EINVAL;
         if (mddev->sync_thread || mddev->reshape_position != MaxSector)
                 return -EBUSY;
+
+        rdev_for_each(rdev, mddev) {
+                if (mddev->raid_disks < raid_disks &&
+                    rdev->data_offset < rdev->new_data_offset)
+                        return -EINVAL;
+                if (mddev->raid_disks > raid_disks &&
+                    rdev->data_offset > rdev->new_data_offset)
+                        return -EINVAL;
+        }
+
         mddev->delta_disks = raid_disks - mddev->raid_disks;
         if (mddev->delta_disks < 0)
                 mddev->reshape_backwards = 1;
@@ -7709,6 +7861,20 @@ void md_wait_for_blocked_rdev(struct md_rdev *rdev, struct mddev *mddev)
 }
 EXPORT_SYMBOL(md_wait_for_blocked_rdev);
 
+void md_finish_reshape(struct mddev *mddev)
+{
+        /* called be personality module when reshape completes. */
+        struct md_rdev *rdev;
+
+        rdev_for_each(rdev, mddev) {
+                if (rdev->data_offset > rdev->new_data_offset)
+                        rdev->sectors += rdev->data_offset - rdev->new_data_offset;
+                else
+                        rdev->sectors -= rdev->new_data_offset - rdev->data_offset;
+                rdev->data_offset = rdev->new_data_offset;
+        }
+}
+EXPORT_SYMBOL(md_finish_reshape);
 
 /* Bad block management.
  * We can record which blocks on each device are 'bad' and so just
@@ -7957,10 +8123,15 @@ static int md_set_badblocks(struct badblocks *bb, sector_t s, int sectors,
 }
 
 int rdev_set_badblocks(struct md_rdev *rdev, sector_t s, int sectors,
-                       int acknowledged)
+                       int is_new)
 {
-        int rv = md_set_badblocks(&rdev->badblocks,
-                                  s + rdev->data_offset, sectors, acknowledged);
+        int rv;
+        if (is_new)
+                s += rdev->new_data_offset;
+        else
+                s += rdev->data_offset;
+        rv = md_set_badblocks(&rdev->badblocks,
+                              s, sectors, 0);
         if (rv) {
                 /* Make sure they get written out promptly */
                 sysfs_notify_dirent_safe(rdev->sysfs_state);
@@ -8066,11 +8237,15 @@ out:
         return rv;
 }
 
-int rdev_clear_badblocks(struct md_rdev *rdev, sector_t s, int sectors)
+int rdev_clear_badblocks(struct md_rdev *rdev, sector_t s, int sectors,
+                         int is_new)
 {
+        if (is_new)
+                s += rdev->new_data_offset;
+        else
+                s += rdev->data_offset;
         return md_clear_badblocks(&rdev->badblocks,
-                                  s + rdev->data_offset,
-                                  sectors);
+                                  s, sectors);
 }
 EXPORT_SYMBOL_GPL(rdev_clear_badblocks);