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

1 files changed, 11 insertions, 5 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 334d68a17108..66b7f2c5d7e9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -663,7 +663,7 @@ struct block_device {
         void *                  bd_holder;
         int                     bd_holders;
 #ifdef CONFIG_SYSFS
-        struct list_head        bd_holder_list;
+        struct gendisk *        bd_holder_disk; /* for sysfs slave linkng */
 #endif
         struct block_device *   bd_contains;
         unsigned                bd_block_size;
@@ -2042,11 +2042,17 @@ extern int blkdev_put(struct block_device *, fmode_t);
 extern int bd_claim(struct block_device *, void *);
 extern void bd_release(struct block_device *);
 #ifdef CONFIG_SYSFS
-extern int bd_claim_by_disk(struct block_device *, void *, struct gendisk *);
-extern void bd_release_from_disk(struct block_device *, struct gendisk *);
+extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
+extern void bd_unlink_disk_holder(struct block_device *bdev);
 #else
-#define bd_claim_by_disk(bdev, holder, disk)    bd_claim(bdev, holder)
-#define bd_release_from_disk(bdev, disk)        bd_release(bdev)
+static inline int bd_link_disk_holder(struct block_device *bdev,
+                                      struct gendisk *disk)
+{
+        return 0;
+}
+static inline void bd_unlink_disk_holder(struct block_device *bdev)
+{
+}
 #endif
 #endif