btrfs: convert latest_bdev type to btrfs_device and rename

In preparation to fix a bug in btrfs_show_devname().

Convert fs_devices::latest_bdev type from struct block_device to struct
btrfs_device and, rename the member to fs_devices::latest_dev.
So that btrfs_show_devname() can use fs_devices::latest_dev::name.
Tested-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -3231,12 +3231,12 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
 	mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
 	btrfs_init_btree_inode(fs_info);
 
-	invalidate_bdev(fs_devices->latest_bdev);
+	invalidate_bdev(fs_devices->latest_dev->bdev);
 
 	/*
 	 * Read super block and check the signature bytes only
 	 */
-	disk_super = btrfs_read_dev_super(fs_devices->latest_bdev);
+	disk_super = btrfs_read_dev_super(fs_devices->latest_dev->bdev);
 	if (IS_ERR(disk_super)) {
 		err = PTR_ERR(disk_super);
 		goto fail_alloc;
@@ -3473,7 +3473,7 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
 	 * below in btrfs_init_dev_replace().
 	 */
 	btrfs_free_extra_devids(fs_devices);
-	if (!fs_devices->latest_bdev) {
+	if (!fs_devices->latest_dev->bdev) {
 		btrfs_err(fs_info, "failed to read devices");
 		goto fail_tree_roots;
 	}

fs/btrfs/extent_io.c

@@ -3327,7 +3327,7 @@ static int alloc_new_bio(struct btrfs_inode *inode,
 	if (wbc) {
 		struct block_device *bdev;
 
-		bdev = fs_info->fs_devices->latest_bdev;
+		bdev = fs_info->fs_devices->latest_dev->bdev;
 		bio_set_dev(bio, bdev);
 		wbc_init_bio(wbc, bio);
 	}

fs/btrfs/inode.c

@@ -7965,7 +7965,7 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
 		iomap->type = IOMAP_MAPPED;
 	}
 	iomap->offset = start;
-	iomap->bdev = fs_info->fs_devices->latest_bdev;
+	iomap->bdev = fs_info->fs_devices->latest_dev->bdev;
 	iomap->length = len;
 
 	if (write && btrfs_use_zone_append(BTRFS_I(inode), em->block_start))

fs/btrfs/super.c

@@ -1705,7 +1705,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 		goto error_close_devices;
 	}
 
-	bdev = fs_devices->latest_bdev;
+	bdev = fs_devices->latest_dev->bdev;
 	s = sget(fs_type, btrfs_test_super, btrfs_set_super, flags | SB_NOSEC,
 		 fs_info);
 	if (IS_ERR(s)) {

fs/btrfs/volumes.c

@@ -1091,7 +1091,7 @@ void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices)
 	list_for_each_entry(seed_dev, &fs_devices->seed_list, seed_list)
 		__btrfs_free_extra_devids(seed_dev, &latest_dev);
 
-	fs_devices->latest_bdev = latest_dev->bdev;
+	fs_devices->latest_dev = latest_dev;
 
 	mutex_unlock(&uuid_mutex);
 }
@@ -1222,7 +1222,7 @@ static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
 		return -EINVAL;
 
 	fs_devices->opened = 1;
-	fs_devices->latest_bdev = latest_dev->bdev;
+	fs_devices->latest_dev = latest_dev;
 	fs_devices->total_rw_bytes = 0;
 	fs_devices->chunk_alloc_policy = BTRFS_CHUNK_ALLOC_REGULAR;
 	fs_devices->read_policy = BTRFS_READ_POLICY_PID;
@@ -1986,7 +1986,7 @@ static struct btrfs_device * btrfs_find_next_active_device(
 }
 
 /*
- * Helper function to check if the given device is part of s_bdev / latest_bdev
+ * Helper function to check if the given device is part of s_bdev / latest_dev
  * and replace it with the provided or the next active device, in the context
  * where this function called, there should be always be another device (or
  * this_dev) which is active.
@@ -2005,8 +2005,8 @@ void __cold btrfs_assign_next_active_device(struct btrfs_device *device,
 			(fs_info->sb->s_bdev == device->bdev))
 		fs_info->sb->s_bdev = next_device->bdev;
 
-	if (fs_info->fs_devices->latest_bdev == device->bdev)
-		fs_info->fs_devices->latest_bdev = next_device->bdev;
+	if (fs_info->fs_devices->latest_dev->bdev == device->bdev)
+		fs_info->fs_devices->latest_dev = next_device;
 }
 
 /*

fs/btrfs/volumes.h

@@ -246,7 +246,11 @@ struct btrfs_fs_devices {
 	/* Highest generation number of seen devices */
 	u64 latest_generation;
 
-	struct block_device *latest_bdev;
+	/*
+	 * The mount device or a device with highest generation after removal
+	 * or replace.
+	 */
+	struct btrfs_device *latest_dev;
 
 	/* all of the devices in the FS, protected by a mutex
 	 * so we can safely walk it to write out the supers without