block: use the holder as indication for exclusive opens

The current interface for exclusive opens is rather confusing as it
requires both the FMODE_EXCL flag and a holder.  Remove the need to pass
FMODE_EXCL and just key off the exclusive open off a non-NULL holder.

For blkdev_put this requires adding the holder argument, which provides
better debug checking that only the holder actually releases the hold,
but at the same time allows removing the now superfluous mode argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Christian Brauner <brauner@kernel.org>
Acked-by: David Sterba <dsterba@suse.com>		[btrfs]
Acked-by: Jack Wang <jinpu.wang@ionos.com>		[rnbd]
Link: https://lore.kernel.org/r/20230608110258.189493-16-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 14 insertions, 9 deletions

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index cab59dab3410..10b1e5171332 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1640,8 +1640,7 @@ static struct block_device *open_backing_dev(struct drbd_device *device,
 	struct block_device *bdev;
 	int err = 0;
 
-	bdev = blkdev_get_by_path(bdev_path,
-				  FMODE_READ | FMODE_WRITE | FMODE_EXCL,
+	bdev = blkdev_get_by_path(bdev_path, FMODE_READ | FMODE_WRITE,
 				  claim_ptr, NULL);
 	if (IS_ERR(bdev)) {
 		drbd_err(device, "open(\"%s\") failed with %ld\n",
@@ -1654,7 +1653,7 @@ static struct block_device *open_backing_dev(struct drbd_device *device,
 
 	err = bd_link_disk_holder(bdev, device->vdisk);
 	if (err) {
-		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+		blkdev_put(bdev, claim_ptr);
 		drbd_err(device, "bd_link_disk_holder(\"%s\", ...) failed with %d\n",
 				bdev_path, err);
 		bdev = ERR_PTR(err);
@@ -1696,13 +1695,13 @@ static int open_backing_devices(struct drbd_device *device,
 }
 
 static void close_backing_dev(struct drbd_device *device, struct block_device *bdev,
-	bool do_bd_unlink)
+		void *claim_ptr, 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);
+	blkdev_put(bdev, claim_ptr);
 }
 
 void drbd_backing_dev_free(struct drbd_device *device, struct drbd_backing_dev *ldev)
@@ -1710,8 +1709,11 @@ void drbd_backing_dev_free(struct drbd_device *device, struct drbd_backing_dev *
 	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);
+	close_backing_dev(device, ldev->md_bdev,
+			  ldev->md.meta_dev_idx < 0 ?
+				(void *)device : (void *)drbd_m_holder,
+			  ldev->md_bdev != ldev->backing_bdev);
+	close_backing_dev(device, ldev->backing_bdev, device, true);
 
 	kfree(ldev->disk_conf);
 	kfree(ldev);
@@ -2127,8 +2129,11 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
  fail:
 	conn_reconfig_done(connection);
 	if (nbc) {
-		close_backing_dev(device, nbc->md_bdev, nbc->md_bdev != nbc->backing_bdev);
-		close_backing_dev(device, nbc->backing_bdev, true);
+		close_backing_dev(device, nbc->md_bdev,
+			  nbc->disk_conf->meta_dev_idx < 0 ?
+				(void *)device : (void *)drbd_m_holder,
+			  nbc->md_bdev != nbc->backing_bdev);
+		close_backing_dev(device, nbc->backing_bdev, device, true);
 		kfree(nbc);
 	}
 	kfree(new_disk_conf);