md: reject a re-add request that cannot be honoured.

The 'add_new_disk' ioctl can be used to add a device either as a
spare, or as an active disk that just needs to be resynced based on
write-intent-bitmap information (re-add)

Currently if a re-add is requested but fails we add as a spare
instead.  This makes it impossible for user-space to check for
failure.

So change to require that a re-add attempt will either succeed or
completely fail.  User-space can then decide what to do next.

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

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4a4c0f80bdeb..5469ae35ee15 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5216,6 +5216,16 @@ static int add_new_disk(mddev_t * mddev, mdu_disk_info_t *info)
                 } else
                         super_types[mddev->major_version].
                                 validate_super(mddev, rdev);
+                if ((info->state & (1<<MD_DISK_SYNC)) &&
+                    (!test_bit(In_sync, &rdev->flags) ||
+                     rdev->raid_disk != info->raid_disk)) {
+                        /* This was a hot-add request, but events doesn't
+                         * match, so reject it.
+                         */
+                        export_rdev(rdev);
+                        return -EINVAL;
+                }
+
                 if (test_bit(In_sync, &rdev->flags))
                         rdev->saved_raid_disk = rdev->raid_disk;
                 else