nilfs2: fix backing_dev_info reference leak

setup_bdev_super() already initializes sb->s_bdev and takes a
reference on the block device backing_dev_info when assigning sb->s_bdi.

nilfs_fill_super() takes another reference to the same
backing_dev_info and stores it in sb->s_bdi again. The extra
reference is not paired with a matching bdi_put(), since
generic_shutdown_super() releases sb->s_bdi only once.

Drop the redundant bdi_get() in nilfs_fill_super(). The single
reference taken by setup_bdev_super() is enough and is released
during superblock shutdown.

Fixes: c1e012e ("nilfs2: use setup_bdev_super to de-duplicate the mount code")
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>

Author: shuangpeng-kernel

fs/nilfs2/super.c

@@ -1070,8 +1070,6 @@ nilfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	sb->s_time_gran = 1;
 	sb->s_max_links = NILFS_LINK_MAX;
 
-	sb->s_bdi = bdi_get(sb->s_bdev->bd_disk->bdi);
-
 	err = load_nilfs(nilfs, sb);
 	if (err)
 		goto failed_nilfs;