drbd: make drbd known to lsblk: use bd_link_disk_holder

lsblk should be able to pick up stacking device driver relations
involving DRBD conveniently.

Even though upstream kernel since 2011 says
	"DON'T USE THIS UNLESS YOU'RE ALREADY USING IT."
a new user has been added since (bcache),
which sets the precedences for us to use it as well.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

5 files changed, 91 insertions, 52 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 08f266eab3ee..a26265375e1e 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1126,7 +1126,7 @@ extern int drbd_send_ov_request(struct drbd_peer_device *, sector_t sector, int
 extern int drbd_send_bitmap(struct drbd_device *device);
 extern void drbd_send_sr_reply(struct drbd_peer_device *, enum drbd_state_rv retcode);
 extern void conn_send_sr_reply(struct drbd_connection *connection, enum drbd_state_rv retcode);
-extern void drbd_free_ldev(struct drbd_backing_dev *ldev);
+extern void drbd_backing_dev_free(struct drbd_device *device, struct drbd_backing_dev *ldev);
 extern void drbd_device_cleanup(struct drbd_device *device);
 void drbd_print_uuids(struct drbd_device *device, const char *text);
 
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index a4aa7eb5507d..136fa733a15e 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1992,7 +1992,7 @@ void drbd_device_cleanup(struct drbd_device *device)
                 drbd_bm_cleanup(device);
         }
 
-        drbd_free_ldev(device->ldev);
+        drbd_backing_dev_free(device, device->ldev);
         device->ldev = NULL;
 
         clear_bit(AL_SUSPENDED, &device->flags);
@@ -2171,7 +2171,7 @@ void drbd_destroy_device(struct kref *kref)
         if (device->this_bdev)
                 bdput(device->this_bdev);
 
-        drbd_free_ldev(device->ldev);
+        drbd_backing_dev_free(device, device->ldev);
         device->ldev = NULL;
 
         drbd_release_all_peer_reqs(device);
@@ -2964,18 +2964,6 @@ fail:
         return err;
 }
 
-void drbd_free_ldev(struct drbd_backing_dev *ldev)
-{
-        if (ldev == NULL)
-                return;
-
-        blkdev_put(ldev->backing_bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
-        blkdev_put(ldev->md_bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
-
-        kfree(ldev->disk_conf);
-        kfree(ldev);
-}
-
 static void drbd_free_one_sock(struct drbd_socket *ds)
 {
         struct socket *s;
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 4703f1ad7f92..ee34739ee9ff 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1471,6 +1471,88 @@ success:
         return 0;
 }
 
+static struct block_device *open_backing_dev(struct drbd_device *device,
+                const char *bdev_path, void *claim_ptr, bool do_bd_link)
+{
+        struct block_device *bdev;
+        int err = 0;
+
+        bdev = blkdev_get_by_path(bdev_path,
+                                  FMODE_READ | FMODE_WRITE | FMODE_EXCL, claim_ptr);
+        if (IS_ERR(bdev)) {
+                drbd_err(device, "open(\"%s\") failed with %ld\n",
+                                bdev_path, PTR_ERR(bdev));
+                return bdev;
+        }
+
+        if (!do_bd_link)
+                return bdev;
+
+        err = bd_link_disk_holder(bdev, device->vdisk);
+        if (err) {
+                blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+                drbd_err(device, "bd_link_disk_holder(\"%s\", ...) failed with %d\n",
+                                bdev_path, err);
+                bdev = ERR_PTR(err);
+        }
+        return bdev;
+}
+
+static int open_backing_devices(struct drbd_device *device,
+                struct disk_conf *new_disk_conf,
+                struct drbd_backing_dev *nbc)
+{
+        struct block_device *bdev;
+
+        bdev = open_backing_dev(device, new_disk_conf->backing_dev, device, true);
+        if (IS_ERR(bdev))
+                return ERR_OPEN_DISK;
+        nbc->backing_bdev = bdev;
+
+        /*
+         * meta_dev_idx >= 0: external fixed size, possibly multiple
+         * drbd sharing one meta device.  TODO in that case, paranoia
+         * check that [md_bdev, meta_dev_idx] is not yet used by some
+         * other drbd minor!  (if you use drbd.conf + drbdadm, that
+         * should check it for you already; but if you don't, or
+         * someone fooled it, we need to double check here)
+         */
+        bdev = open_backing_dev(device, new_disk_conf->meta_dev,
+                /* claim ptr: device, if claimed exclusively; shared drbd_m_holder,
+                 * if potentially shared with other drbd minors */
+                        (new_disk_conf->meta_dev_idx < 0) ? (void*)device : (void*)drbd_m_holder,
+                /* avoid double bd_claim_by_disk() for the same (source,target) tuple,
+                 * as would happen with internal metadata. */
+                        (new_disk_conf->meta_dev_idx != DRBD_MD_INDEX_FLEX_INT &&
+                         new_disk_conf->meta_dev_idx != DRBD_MD_INDEX_INTERNAL));
+        if (IS_ERR(bdev))
+                return ERR_OPEN_MD_DISK;
+        nbc->md_bdev = bdev;
+        return NO_ERROR;
+}
+
+static void close_backing_dev(struct drbd_device *device, struct block_device *bdev,
+        bool do_bd_unlink)
+{
+        if (!bdev)
+                return;
+        if (do_bd_unlink)
+                bd_unlink_disk_holder(bdev, device->vdisk);
+        blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+}
+
+void drbd_backing_dev_free(struct drbd_device *device, struct drbd_backing_dev *ldev)
+{
+        if (ldev == NULL)
+                return;
+
+        close_backing_dev(device, ldev->md_bdev, ldev->md_bdev != ldev->backing_bdev);
+        close_backing_dev(device, ldev->backing_bdev, true);
+
+        kfree(ldev->disk_conf);
+        kfree(ldev);
+}
+
 int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 {
         struct drbd_config_context adm_ctx;
@@ -1484,7 +1566,6 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
         sector_t min_md_device_sectors;
         struct drbd_backing_dev *nbc = NULL; /* new_backing_conf */
         struct disk_conf *new_disk_conf = NULL;
-        struct block_device *bdev;
         struct lru_cache *resync_lru = NULL;
         struct fifo_buffer *new_plan = NULL;
         union drbd_state ns, os;
@@ -1572,35 +1653,9 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
         }
         rcu_read_unlock();
 
-        bdev = blkdev_get_by_path(new_disk_conf->backing_dev,
-                                  FMODE_READ | FMODE_WRITE | FMODE_EXCL, device);
-        if (IS_ERR(bdev)) {
-                drbd_err(device, "open(\"%s\") failed with %ld\n", new_disk_conf->backing_dev,
-                        PTR_ERR(bdev));
-                retcode = ERR_OPEN_DISK;
-                goto fail;
-        }
-        nbc->backing_bdev = bdev;
-
-        /*
-         * meta_dev_idx >= 0: external fixed size, possibly multiple
-         * drbd sharing one meta device.  TODO in that case, paranoia
-         * check that [md_bdev, meta_dev_idx] is not yet used by some
-         * other drbd minor!  (if you use drbd.conf + drbdadm, that
-         * should check it for you already; but if you don't, or
-         * someone fooled it, we need to double check here)
-         */
-        bdev = blkdev_get_by_path(new_disk_conf->meta_dev,
-                                  FMODE_READ | FMODE_WRITE | FMODE_EXCL,
-                                  (new_disk_conf->meta_dev_idx < 0) ?
-                                  (void *)device : (void *)drbd_m_holder);
-        if (IS_ERR(bdev)) {
-                drbd_err(device, "open(\"%s\") failed with %ld\n", new_disk_conf->meta_dev,
-                        PTR_ERR(bdev));
-                retcode = ERR_OPEN_MD_DISK;
+        retcode = open_backing_devices(device, new_disk_conf, nbc);
+        if (retcode != NO_ERROR)
                 goto fail;
-        }
-        nbc->md_bdev = bdev;
 
         if ((nbc->backing_bdev == nbc->md_bdev) !=
             (new_disk_conf->meta_dev_idx == DRBD_MD_INDEX_INTERNAL ||
@@ -1900,12 +1955,8 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
  fail:
         conn_reconfig_done(connection);
         if (nbc) {
-                if (nbc->backing_bdev)
-                        blkdev_put(nbc->backing_bdev,
-                                   FMODE_READ | FMODE_WRITE | FMODE_EXCL);
-                if (nbc->md_bdev)
-                        blkdev_put(nbc->md_bdev,
-                                   FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+                close_backing_dev(device, nbc->md_bdev, nbc->md_bdev != nbc->backing_bdev);
+                close_backing_dev(device, nbc->backing_bdev, true);
                 kfree(nbc);
         }
         kfree(new_disk_conf);
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 2f29bf3e4dba..eff716c27b1f 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -1841,7 +1841,7 @@ static void drbd_ldev_destroy(struct drbd_device *device)
         device->act_log = NULL;
 
         __acquire(local);
-        drbd_free_ldev(device->ldev);
+        drbd_backing_dev_free(device, device->ldev);
         device->ldev = NULL;
         __release(local);
 
diff --git a/include/linux/drbd.h b/include/linux/drbd.h
index 392fc0edb516..d6b3c9943a2c 100644
--- a/include/linux/drbd.h
+++ b/include/linux/drbd.h
@@ -51,7 +51,7 @@
 #endif
 
 extern const char *drbd_buildtag(void);
-#define REL_VERSION "8.4.5"
+#define REL_VERSION "8.4.6"
 #define API_VERSION 1
 #define PRO_VERSION_MIN 86
 #define PRO_VERSION_MAX 101