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>

5 files changed, 27 insertions, 23 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);
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 7bfc058cb665..c3299e49edd5 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -2167,8 +2167,7 @@ static int pkt_open_dev(struct pktcdvd_device *pd, fmode_t write)
 	 * to read/write from/to it. It is already opened in O_NONBLOCK mode
 	 * so open should not fail.
 	 */
-	bdev = blkdev_get_by_dev(pd->bdev->bd_dev, FMODE_READ | FMODE_EXCL, pd,
-				 NULL);
+	bdev = blkdev_get_by_dev(pd->bdev->bd_dev, FMODE_READ, pd, NULL);
 	if (IS_ERR(bdev)) {
 		ret = PTR_ERR(bdev);
 		goto out;
@@ -2215,7 +2214,7 @@ static int pkt_open_dev(struct pktcdvd_device *pd, fmode_t write)
 	return 0;
 
 out_putdev:
-	blkdev_put(bdev, FMODE_READ | FMODE_EXCL);
+	blkdev_put(bdev, pd);
 out:
 	return ret;
 }
@@ -2234,7 +2233,7 @@ static void pkt_release_dev(struct pktcdvd_device *pd, int flush)
 	pkt_lock_door(pd, 0);
 
 	pkt_set_speed(pd, MAX_SPEED, MAX_SPEED);
-	blkdev_put(pd->bdev, FMODE_READ | FMODE_EXCL);
+	blkdev_put(pd->bdev, pd);
 
 	pkt_shrink_pktlist(pd);
 }
@@ -2520,7 +2519,7 @@ static int pkt_new_dev(struct pktcdvd_device *pd, dev_t dev)
 		return PTR_ERR(bdev);
 	sdev = scsi_device_from_queue(bdev->bd_disk->queue);
 	if (!sdev) {
-		blkdev_put(bdev, FMODE_READ | FMODE_NDELAY);
+		blkdev_put(bdev, NULL);
 		return -EINVAL;
 	}
 	put_device(&sdev->sdev_gendev);
@@ -2545,7 +2544,7 @@ static int pkt_new_dev(struct pktcdvd_device *pd, dev_t dev)
 	return 0;
 
 out_mem:
-	blkdev_put(bdev, FMODE_READ | FMODE_NDELAY);
+	blkdev_put(bdev, NULL);
 	/* This is safe: open() is still holding a reference. */
 	module_put(THIS_MODULE);
 	return -ENOMEM;
@@ -2751,7 +2750,7 @@ static int pkt_remove_dev(dev_t pkt_dev)
 	pkt_debugfs_dev_remove(pd);
 	pkt_sysfs_dev_remove(pd);
 
-	blkdev_put(pd->bdev, FMODE_READ | FMODE_NDELAY);
+	blkdev_put(pd->bdev, NULL);
 
 	remove_proc_entry(pd->disk->disk_name, pkt_proc);
 	dev_notice(ddev, "writer unmapped\n");
diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c
index a92a4289d0ec..a909f8763ce7 100644
--- a/drivers/block/rnbd/rnbd-srv.c
+++ b/drivers/block/rnbd/rnbd-srv.c
@@ -219,7 +219,7 @@ void rnbd_destroy_sess_dev(struct rnbd_srv_sess_dev *sess_dev, bool keep_id)
 	rnbd_put_sess_dev(sess_dev);
 	wait_for_completion(&dc); /* wait for inflights to drop to zero */
 
-	blkdev_put(sess_dev->bdev, sess_dev->open_flags);
+	blkdev_put(sess_dev->bdev, NULL);
 	mutex_lock(&sess_dev->dev->lock);
 	list_del(&sess_dev->dev_list);
 	if (sess_dev->open_flags & FMODE_WRITE)
@@ -791,7 +791,7 @@ srv_dev_put:
 	}
 	rnbd_put_srv_dev(srv_dev);
 blkdev_put:
-	blkdev_put(bdev, open_flags);
+	blkdev_put(bdev, NULL);
 free_path:
 	kfree(full_path);
 reject:
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 43b36da9b354..141b60aad570 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -473,7 +473,7 @@ static void xenvbd_sysfs_delif(struct xenbus_device *dev)
 static void xen_vbd_free(struct xen_vbd *vbd)
 {
 	if (vbd->bdev)
-		blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
+		blkdev_put(vbd->bdev, NULL);
 	vbd->bdev = NULL;
 }
 
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index f5644c606040..21615d67a9bd 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -420,7 +420,7 @@ static void reset_bdev(struct zram *zram)
 		return;
 
 	bdev = zram->bdev;
-	blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+	blkdev_put(bdev, zram);
 	/* hope filp_close flush all of IO */
 	filp_close(zram->backing_dev, NULL);
 	zram->backing_dev = NULL;
@@ -507,8 +507,8 @@ static ssize_t backing_dev_store(struct device *dev,
 		goto out;
 	}
 
-	bdev = blkdev_get_by_dev(inode->i_rdev,
-			FMODE_READ | FMODE_WRITE | FMODE_EXCL, zram, NULL);
+	bdev = blkdev_get_by_dev(inode->i_rdev, FMODE_READ | FMODE_WRITE, zram,
+				 NULL);
 	if (IS_ERR(bdev)) {
 		err = PTR_ERR(bdev);
 		bdev = NULL;
@@ -539,7 +539,7 @@ out:
 	kvfree(bitmap);
 
 	if (bdev)
-		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+		blkdev_put(bdev, zram);
 
 	if (backing_dev)
 		filp_close(backing_dev, NULL);