block: Add invalidate_disk() helper to invalidate the gendisk

To hide internal implementation and simplify some driver code,
this adds a helper to invalidate the gendisk. It will clean the
gendisk's associated buffer/page caches and reset its internal
states.
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210922123711.187-2-xieyongji@bytedance.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -624,6 +624,26 @@ void del_gendisk(struct gendisk *disk)
 }
 EXPORT_SYMBOL(del_gendisk);
 
+/**
+ * invalidate_disk - invalidate the disk
+ * @disk: the struct gendisk to invalidate
+ *
+ * A helper to invalidates the disk. It will clean the disk's associated
+ * buffer/page caches and reset its internal states so that the disk
+ * can be reused by the drivers.
+ *
+ * Context: can sleep
+ */
+void invalidate_disk(struct gendisk *disk)
+{
+	struct block_device *bdev = disk->part0;
+
+	invalidate_bdev(bdev);
+	bdev->bd_inode->i_mapping->wb_err = 0;
+	set_capacity(disk, 0);
+}
+EXPORT_SYMBOL(invalidate_disk);
+
 /* sysfs access to bad-blocks list. */
 static ssize_t disk_badblocks_show(struct device *dev,
 					struct device_attribute *attr,

include/linux/genhd.h

@@ -213,6 +213,8 @@ static inline int add_disk(struct gendisk *disk)
 }
 extern void del_gendisk(struct gendisk *gp);
 
+void invalidate_disk(struct gendisk *disk);
+
 void set_disk_ro(struct gendisk *disk, bool read_only);
 
 static inline int get_disk_ro(struct gendisk *disk)