block: move bd_mutex to struct gendisk

Replace the per-block device bd_mutex with a per-gendisk open_mutex,
thus simplifying locking wherever we deal with partitions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Link: https://lore.kernel.org/r/20210525061301.2242282-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

3 files changed, 20 insertions, 27 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 41d2d9708bf8..e094806c3a0c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -895,7 +895,6 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
 	mapping_set_gfp_mask(&inode->i_data, GFP_USER);
 
 	bdev = I_BDEV(inode);
-	mutex_init(&bdev->bd_mutex);
 	mutex_init(&bdev->bd_fsfreeze_mutex);
 	spin_lock_init(&bdev->bd_size_lock);
 	bdev->bd_disk = disk;
@@ -1154,7 +1153,7 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 	struct bd_holder_disk *holder;
 	int ret = 0;
 
-	mutex_lock(&bdev->bd_mutex);
+	mutex_lock(&bdev->bd_disk->open_mutex);
 
 	WARN_ON_ONCE(!bdev->bd_holder);
 
@@ -1199,7 +1198,7 @@ out_del:
 out_free:
 	kfree(holder);
 out_unlock:
-	mutex_unlock(&bdev->bd_mutex);
+	mutex_unlock(&bdev->bd_disk->open_mutex);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(bd_link_disk_holder);
@@ -1218,7 +1217,7 @@ void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
 {
 	struct bd_holder_disk *holder;
 
-	mutex_lock(&bdev->bd_mutex);
+	mutex_lock(&bdev->bd_disk->open_mutex);
 
 	holder = bd_find_holder_disk(bdev, disk);
 
@@ -1230,7 +1229,7 @@ void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
 		kfree(holder);
 	}
 
-	mutex_unlock(&bdev->bd_mutex);
+	mutex_unlock(&bdev->bd_disk->open_mutex);
 }
 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
 #endif
@@ -1242,7 +1241,7 @@ int bdev_disk_changed(struct block_device *bdev, bool invalidate)
 	struct gendisk *disk = bdev->bd_disk;
 	int ret = 0;
 
-	lockdep_assert_held(&bdev->bd_mutex);
+	lockdep_assert_held(&disk->open_mutex);
 
 	if (!(disk->flags & GENHD_FL_UP))
 		return -ENXIO;
@@ -1327,14 +1326,10 @@ static int blkdev_get_part(struct block_device *part, fmode_t mode)
 		goto done;
 
 	whole = bdgrab(disk->part0);
-	mutex_lock_nested(&whole->bd_mutex, 1);
 	ret = blkdev_get_whole(whole, mode);
-	if (ret) {
-		mutex_unlock(&whole->bd_mutex);
+	if (ret)
 		goto out_put_whole;
-	}
 	whole->bd_part_count++;
-	mutex_unlock(&whole->bd_mutex);
 
 	ret = -ENXIO;
 	if (!bdev_nr_sectors(part))
@@ -1437,7 +1432,7 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
 
 	disk_block_events(disk);
 
-	mutex_lock(&bdev->bd_mutex);
+	mutex_lock(&disk->open_mutex);
 	ret = -ENXIO;
 	if (!(disk->flags & GENHD_FL_UP))
 		goto abort_claiming;
@@ -1463,7 +1458,7 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
 			unblock_events = false;
 		}
 	}
-	mutex_unlock(&bdev->bd_mutex);
+	mutex_unlock(&disk->open_mutex);
 
 	if (unblock_events)
 		disk_unblock_events(disk);
@@ -1472,7 +1467,7 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
 abort_claiming:
 	if (mode & FMODE_EXCL)
 		bd_abort_claiming(bdev, holder);
-	mutex_unlock(&bdev->bd_mutex);
+	mutex_unlock(&disk->open_mutex);
 	disk_unblock_events(disk);
 put_blkdev:
 	blkdev_put_no_open(bdev);
@@ -1552,7 +1547,6 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
 	struct gendisk *disk = bdev->bd_disk;
 	struct block_device *victim = NULL;
 
-	mutex_lock_nested(&bdev->bd_mutex, for_part);
 	if (for_part)
 		bdev->bd_part_count--;
 
@@ -1567,7 +1561,6 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
 
 	if (!bdev_is_partition(bdev) && disk->fops->release)
 		disk->fops->release(disk, mode);
-	mutex_unlock(&bdev->bd_mutex);
 	if (victim) {
 		__blkdev_put(victim, mode, 1);
 		bdput(victim);
@@ -1588,15 +1581,14 @@ void blkdev_put(struct block_device *bdev, fmode_t mode)
 	if (bdev->bd_openers == 1)
 		sync_blockdev(bdev);
 
-	mutex_lock(&bdev->bd_mutex);
-
+	mutex_lock(&disk->open_mutex);
 	if (mode & FMODE_EXCL) {
 		struct block_device *whole = bdev_whole(bdev);
 		bool bdev_free;
 
 		/*
 		 * Release a claim on the device.  The holder fields
-		 * are protected with bdev_lock.  bd_mutex is to
+		 * are protected with bdev_lock.  open_mutex is to
 		 * synchronize disk_holder unlinking.
 		 */
 		spin_lock(&bdev_lock);
@@ -1627,9 +1619,10 @@ void blkdev_put(struct block_device *bdev, fmode_t mode)
 	 * from userland - e.g. eject(1).
 	 */
 	disk_flush_events(disk, DISK_EVENT_MEDIA_CHANGE);
-	mutex_unlock(&bdev->bd_mutex);
 
 	__blkdev_put(bdev, mode, 0);
+	mutex_unlock(&disk->open_mutex);
+
 	blkdev_put_no_open(bdev);
 }
 EXPORT_SYMBOL(blkdev_put);
@@ -1936,10 +1929,10 @@ void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
 		old_inode = inode;
 		bdev = I_BDEV(inode);
 
-		mutex_lock(&bdev->bd_mutex);
+		mutex_lock(&bdev->bd_disk->open_mutex);
 		if (bdev->bd_openers)
 			func(bdev, arg);
-		mutex_unlock(&bdev->bd_mutex);
+		mutex_unlock(&bdev->bd_disk->open_mutex);
 
 		spin_lock(&blockdev_superblock->s_inode_list_lock);
 	}
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 47d27059d064..f246eb2772e9 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1247,7 +1247,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 	lockdep_assert_held(&uuid_mutex);
 	/*
 	 * The device_list_mutex cannot be taken here in case opening the
-	 * underlying device takes further locks like bd_mutex.
+	 * underlying device takes further locks like open_mutex.
 	 *
 	 * We also don't need the lock here as this is called during mount and
 	 * exclusion is provided by uuid_mutex
diff --git a/fs/super.c b/fs/super.c
index 11b7e7213fd1..91b7f156735b 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1277,9 +1277,9 @@ int get_tree_bdev(struct fs_context *fc,
 		}
 
 		/*
-		 * s_umount nests inside bd_mutex during
+		 * s_umount nests inside open_mutex during
 		 * __invalidate_device().  blkdev_put() acquires
-		 * bd_mutex and can't be called under s_umount.  Drop
+		 * open_mutex and can't be called under s_umount.  Drop
 		 * s_umount temporarily.  This is safe as we're
 		 * holding an active reference.
 		 */
@@ -1352,9 +1352,9 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 		}
 
 		/*
-		 * s_umount nests inside bd_mutex during
+		 * s_umount nests inside open_mutex during
 		 * __invalidate_device().  blkdev_put() acquires
-		 * bd_mutex and can't be called under s_umount.  Drop
+		 * open_mutex and can't be called under s_umount.  Drop
 		 * s_umount temporarily.  This is safe as we're
 		 * holding an active reference.
 		 */