block: simplify holder symlink handling

Code to manage symlinks in /sys/block/*/{holders|slaves} are overly
complex with multiple holder considerations, redundant extra
references to all involved kobjects, unused generic kobject holder
support and unnecessary mixup with bd_claim/release functionalities.

Strip it down to what's necessary (single gendisk holder) and make it
use a separate interface.  This is a step for cleaning up
bd_claim/release.  This patch makes dm-table slightly more complex but
it will be simplified again with further changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Brown <neilb@suse.de>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Cc: dm-devel@redhat.com

2 files changed, 19 insertions, 8 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 90267f8d64ee..2c876ffc63df 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -328,12 +328,22 @@ static int open_dev(struct dm_dev_internal *d, dev_t dev,
         bdev = open_by_devnum(dev, d->dm_dev.mode);
         if (IS_ERR(bdev))
                 return PTR_ERR(bdev);
-        r = bd_claim_by_disk(bdev, _claim_ptr, dm_disk(md));
-        if (r)
+
+        r = bd_claim(bdev, _claim_ptr);
+        if (r) {
                 blkdev_put(bdev, d->dm_dev.mode);
-        else
-                d->dm_dev.bdev = bdev;
-        return r;
+                return r;
+        }
+
+        r = bd_link_disk_holder(bdev, dm_disk(md));
+        if (r) {
+                bd_release(bdev);
+                blkdev_put(bdev, d->dm_dev.mode);
+                return r;
+        }
+
+        d->dm_dev.bdev = bdev;
+        return 0;
 }
 
 /*
@@ -344,7 +354,8 @@ static void close_dev(struct dm_dev_internal *d, struct mapped_device *md)
         if (!d->dm_dev.bdev)
                 return;
 
-        bd_release_from_disk(d->dm_dev.bdev, dm_disk(md));
+        bd_unlink_disk_holder(d->dm_dev.bdev);
+        bd_release(d->dm_dev.bdev);
         blkdev_put(d->dm_dev.bdev, d->dm_dev.mode);
         d->dm_dev.bdev = NULL;
 }
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4e957f3140a8..c47644fca1a1 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1880,7 +1880,7 @@ static int bind_rdev_to_array(mdk_rdev_t * rdev, mddev_t * mddev)
         rdev->sysfs_state = sysfs_get_dirent_safe(rdev->kobj.sd, "state");
 
         list_add_rcu(&rdev->same_set, &mddev->disks);
-        bd_claim_by_disk(rdev->bdev, rdev->bdev->bd_holder, mddev->gendisk);
+        bd_link_disk_holder(rdev->bdev, mddev->gendisk);
 
         /* May as well allow recovery to be retried once */
         mddev->recovery_disabled = 0;
@@ -1907,7 +1907,7 @@ static void unbind_rdev_from_array(mdk_rdev_t * rdev)
                 MD_BUG();
                 return;
         }
-        bd_release_from_disk(rdev->bdev, rdev->mddev->gendisk);
+        bd_unlink_disk_holder(rdev->bdev);
         list_del_rcu(&rdev->same_set);
         printk(KERN_INFO "md: unbind<%s>\n", bdevname(rdev->bdev,b));
         rdev->mddev = NULL;