md/raid1: add takeover support for raid5->raid1

A 2-device raid5 array can now be converted to raid1.

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

2 files changed, 120 insertions, 76 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 35b2d8646ae9..7549b0bad326 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -677,6 +677,7 @@ static void raise_barrier(conf_t *conf)
 static void lower_barrier(conf_t *conf)
 {
         unsigned long flags;
+        BUG_ON(conf->barrier <= 0);
         spin_lock_irqsave(&conf->resync_lock, flags);
         conf->barrier--;
         spin_unlock_irqrestore(&conf->resync_lock, flags);
@@ -1960,74 +1961,48 @@ static sector_t raid1_size(mddev_t *mddev, sector_t sectors, int raid_disks)
         return mddev->dev_sectors;
 }
 
-static int run(mddev_t *mddev)
+static conf_t *setup_conf(mddev_t *mddev)
 {
         conf_t *conf;
-        int i, j, disk_idx;
+        int i;
         mirror_info_t *disk;
         mdk_rdev_t *rdev;
+        int err = -ENOMEM;
 
-        if (mddev->level != 1) {
-                printk("raid1: %s: raid level not set to mirroring (%d)\n",
-                       mdname(mddev), mddev->level);
-                goto out;
-        }
-        if (mddev->reshape_position != MaxSector) {
-                printk("raid1: %s: reshape_position set but not supported\n",
-                       mdname(mddev));
-                goto out;
-        }
-        /*
-         * copy the already verified devices into our private RAID1
-         * bookkeeping area. [whatever we allocate in run(),
-         * should be freed in stop()]
-         */
         conf = kzalloc(sizeof(conf_t), GFP_KERNEL);
-        mddev->private = conf;
         if (!conf)
-                goto out_no_mem;
+                goto abort;
 
         conf->mirrors = kzalloc(sizeof(struct mirror_info)*mddev->raid_disks,
                                  GFP_KERNEL);
         if (!conf->mirrors)
-                goto out_no_mem;
+                goto abort;
 
         conf->tmppage = alloc_page(GFP_KERNEL);
         if (!conf->tmppage)
-                goto out_no_mem;
+                goto abort;
 
-        conf->poolinfo = kmalloc(sizeof(*conf->poolinfo), GFP_KERNEL);
+        conf->poolinfo = kzalloc(sizeof(*conf->poolinfo), GFP_KERNEL);
         if (!conf->poolinfo)
-                goto out_no_mem;
-        conf->poolinfo->mddev = NULL;
+                goto abort;
         conf->poolinfo->raid_disks = mddev->raid_disks;
         conf->r1bio_pool = mempool_create(NR_RAID1_BIOS, r1bio_pool_alloc,
                                           r1bio_pool_free,
                                           conf->poolinfo);
         if (!conf->r1bio_pool)
-                goto out_no_mem;
+                goto abort;
+
         conf->poolinfo->mddev = mddev;
 
         spin_lock_init(&conf->device_lock);
-        mddev->queue->queue_lock = &conf->device_lock;
-
         list_for_each_entry(rdev, &mddev->disks, same_set) {
-                disk_idx = rdev->raid_disk;
+                int disk_idx = rdev->raid_disk;
                 if (disk_idx >= mddev->raid_disks
                     || disk_idx < 0)
                         continue;
                 disk = conf->mirrors + disk_idx;
 
                 disk->rdev = rdev;
-                disk_stack_limits(mddev->gendisk, rdev->bdev,
-                                  rdev->data_offset << 9);
-                /* as we don't honour merge_bvec_fn, we must never risk
-                 * violating it, so limit ->max_sector to one PAGE, as
-                 * a one page request is never in violation.
-                 */
-                if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
-                    queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
-                        blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 
                 disk->head_position = 0;
         }
@@ -2041,8 +2016,7 @@ static int run(mddev_t *mddev)
         bio_list_init(&conf->pending_bio_list);
         bio_list_init(&conf->flushing_bio_list);
 
-
-        mddev->degraded = 0;
+        conf->last_used = -1;
         for (i = 0; i < conf->raid_disks; i++) {
 
                 disk = conf->mirrors + i;
@@ -2050,38 +2024,97 @@ static int run(mddev_t *mddev)
                 if (!disk->rdev ||
                     !test_bit(In_sync, &disk->rdev->flags)) {
                         disk->head_position = 0;
-                        mddev->degraded++;
                         if (disk->rdev)
                                 conf->fullsync = 1;
-                }
+                } else if (conf->last_used < 0)
+                        /*
+                         * The first working device is used as a
+                         * starting point to read balancing.
+                         */
+                        conf->last_used = i;
         }
-        if (mddev->degraded == conf->raid_disks) {
+
+        err = -EIO;
+        if (conf->last_used < 0) {
                 printk(KERN_ERR "raid1: no operational mirrors for %s\n",
-                        mdname(mddev));
-                goto out_free_conf;
+                       mdname(mddev));
+                goto abort;
+        }
+        err = -ENOMEM;
+        conf->thread = md_register_thread(raid1d, mddev, NULL);
+        if (!conf->thread) {
+                printk(KERN_ERR
+                       "raid1: couldn't allocate thread for %s\n",
+                       mdname(mddev));
+                goto abort;
         }
-        if (conf->raid_disks - mddev->degraded == 1)
-                mddev->recovery_cp = MaxSector;
 
+        return conf;
+
+ abort:
+        if (conf) {
+                if (conf->r1bio_pool)
+                        mempool_destroy(conf->r1bio_pool);
+                kfree(conf->mirrors);
+                safe_put_page(conf->tmppage);
+                kfree(conf->poolinfo);
+                kfree(conf);
+        }
+        return ERR_PTR(err);
+}
+
+static int run(mddev_t *mddev)
+{
+        conf_t *conf;
+        int i;
+        mdk_rdev_t *rdev;
+
+        if (mddev->level != 1) {
+                printk("raid1: %s: raid level not set to mirroring (%d)\n",
+                       mdname(mddev), mddev->level);
+                return -EIO;
+        }
+        if (mddev->reshape_position != MaxSector) {
+                printk("raid1: %s: reshape_position set but not supported\n",
+                       mdname(mddev));
+                return -EIO;
+        }
         /*
-         * find the first working one and use it as a starting point
-         * to read balancing.
+         * copy the already verified devices into our private RAID1
+         * bookkeeping area. [whatever we allocate in run(),
+         * should be freed in stop()]
          */
-        for (j = 0; j < conf->raid_disks &&
-                     (!conf->mirrors[j].rdev ||
-                      !test_bit(In_sync, &conf->mirrors[j].rdev->flags)) ; j++)
-                /* nothing */;
-        conf->last_used = j;
+        if (mddev->private == NULL)
+                conf = setup_conf(mddev);
+        else
+                conf = mddev->private;
 
+        if (IS_ERR(conf))
+                return PTR_ERR(conf);
 
-        mddev->thread = md_register_thread(raid1d, mddev, NULL);
-        if (!mddev->thread) {
-                printk(KERN_ERR
-                       "raid1: couldn't allocate thread for %s\n",
-                       mdname(mddev));
-                goto out_free_conf;
+        mddev->queue->queue_lock = &conf->device_lock;
+        list_for_each_entry(rdev, &mddev->disks, same_set) {
+                disk_stack_limits(mddev->gendisk, rdev->bdev,
+                                  rdev->data_offset << 9);
+                /* as we don't honour merge_bvec_fn, we must never risk
+                 * violating it, so limit ->max_sector to one PAGE, as
+                 * a one page request is never in violation.
+                 */
+                if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
+                    queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
+                        blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
         }
 
+        mddev->degraded = 0;
+        for (i=0; i < conf->raid_disks; i++)
+                if (conf->mirrors[i].rdev == NULL ||
+                    !test_bit(In_sync, &conf->mirrors[i].rdev->flags) ||
+                    test_bit(Faulty, &conf->mirrors[i].rdev->flags))
+                        mddev->degraded++;
+
+        if (conf->raid_disks - mddev->degraded == 1)
+                mddev->recovery_cp = MaxSector;
+
         if (mddev->recovery_cp != MaxSector)
                 printk(KERN_NOTICE "raid1: %s is not clean"
                        " -- starting background reconstruction\n",
@@ -2090,9 +2123,14 @@ static int run(mddev_t *mddev)
                 "raid1: raid set %s active with %d out of %d mirrors\n",
                 mdname(mddev), mddev->raid_disks - mddev->degraded, 
                 mddev->raid_disks);
+
         /*
          * Ok, everything is just fine now
          */
+        mddev->thread = conf->thread;
+        conf->thread = NULL;
+        mddev->private = conf;
+
         md_set_array_sectors(mddev, raid1_size(mddev, 0, 0));
 
         mddev->queue->unplug_fn = raid1_unplug;
@@ -2100,23 +2138,6 @@ static int run(mddev_t *mddev)
         mddev->queue->backing_dev_info.congested_data = mddev;
         md_integrity_register(mddev);
         return 0;
-
-out_no_mem:
-        printk(KERN_ERR "raid1: couldn't allocate memory for %s\n",
-               mdname(mddev));
-
-out_free_conf:
-        if (conf) {
-                if (conf->r1bio_pool)
-                        mempool_destroy(conf->r1bio_pool);
-                kfree(conf->mirrors);
-                safe_put_page(conf->tmppage);
-                kfree(conf->poolinfo);
-                kfree(conf);
-                mddev->private = NULL;
-        }
-out:
-        return -EIO;
 }
 
 static int stop(mddev_t *mddev)
@@ -2302,6 +2323,23 @@ static void raid1_quiesce(mddev_t *mddev, int state)
         }
 }
 
+static void *raid1_takeover(mddev_t *mddev)
+{
+        /* raid1 can take over:
+         *  raid5 with 2 devices, any layout or chunk size
+         */
+        if (mddev->level == 5 && mddev->raid_disks == 2) {
+                conf_t *conf;
+                mddev->new_level = 1;
+                mddev->new_layout = 0;
+                mddev->new_chunk_sectors = 0;
+                conf = setup_conf(mddev);
+                if (!IS_ERR(conf))
+                        conf->barrier = 1;
+                return conf;
+        }
+        return ERR_PTR(-EINVAL);
+}
 
 static struct mdk_personality raid1_personality =
 {
@@ -2321,6 +2359,7 @@ static struct mdk_personality raid1_personality =
         .size           = raid1_size,
         .check_reshape  = raid1_reshape,
         .quiesce        = raid1_quiesce,
+        .takeover       = raid1_takeover,
 };
 
 static int __init raid_init(void)
diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
index e87b84deff68..5f2d443ae28a 100644
--- a/drivers/md/raid1.h
+++ b/drivers/md/raid1.h
@@ -59,6 +59,11 @@ struct r1_private_data_s {
 
         mempool_t *r1bio_pool;
         mempool_t *r1buf_pool;
+
+        /* When taking over an array from a different personality, we store
+         * the new thread here until we fully activate the array.
+         */
+        struct mdk_thread_s     *thread;
 };
 
 typedef struct r1_private_data_s conf_t;