md: fix bug with linear hot-add and elsewhere

Adding a drive to a linear array seems to have stopped working, due to changes
elsewhere in md, and insufficient ongoing testing...

So the patch to make linear hot-add work in the first place introduced a
subtle bug elsewhere that interracts poorly with older version of mdadm.

This fixes it all up.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 6 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index c10ce91b64e9..1c54f3c1cca7 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1298,8 +1298,9 @@ static void super_1_sync(mddev_t *mddev, mdk_rdev_t *rdev)
         ITERATE_RDEV(mddev,rdev2,tmp)
                 if (rdev2->desc_nr+1 > max_dev)
                         max_dev = rdev2->desc_nr+1;
-        
-        sb->max_dev = cpu_to_le32(max_dev);
+
+        if (max_dev > le32_to_cpu(sb->max_dev))
+                sb->max_dev = cpu_to_le32(max_dev);
         for (i=0; i<max_dev;i++)
                 sb->dev_roles[i] = cpu_to_le16(0xfffe);
         
@@ -1365,10 +1366,14 @@ static int bind_rdev_to_array(mdk_rdev_t * rdev, mddev_t * mddev)
         }
         /* make sure rdev->size exceeds mddev->size */
         if (rdev->size && (mddev->size == 0 || rdev->size < mddev->size)) {
-                if (mddev->pers)
-                        /* Cannot change size, so fail */
-                        return -ENOSPC;
-                else
+                if (mddev->pers) {
+                        /* Cannot change size, so fail
+                         * If mddev->level <= 0, then we don't care
+                         * about aligning sizes (e.g. linear)
+                         */
+                        if (mddev->level > 0)
+                                return -ENOSPC;
+                } else
                         mddev->size = rdev->size;
         }
 
@@ -2142,6 +2147,9 @@ static void analyze_sbs(mddev_t * mddev)
                         rdev->desc_nr = i++;
                         rdev->raid_disk = rdev->desc_nr;
                         set_bit(In_sync, &rdev->flags);
+                } else if (rdev->raid_disk >= mddev->raid_disks) {
+                        rdev->raid_disk = -1;
+                        clear_bit(In_sync, &rdev->flags);
                 }
         }