block: remove unused copy_io_context()

Reported-by: Oleg Nesterov <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

block/blk-ioc.c

···
 }
 EXPORT_SYMBOL(get_io_context);
 
-void copy_io_context(struct io_context **pdst, struct io_context **psrc)
-{
-	struct io_context *src = *psrc;
-	struct io_context *dst = *pdst;
-
-	if (src) {
-		BUG_ON(atomic_long_read(&src->refcount) == 0);
-		atomic_long_inc(&src->refcount);
-		put_io_context(dst);
-		*pdst = src;
-	}
-}
-EXPORT_SYMBOL(copy_io_context);
-
 static int __init blk_ioc_init(void)
 {
 	iocontext_cachep = kmem_cache_create("blkdev_ioc",

include/linux/iocontext.h

···
 void exit_io_context(struct task_struct *task);
 struct io_context *get_io_context(gfp_t gfp_flags, int node);
 struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
-void copy_io_context(struct io_context **pdst, struct io_context **psrc);
 #else
 static inline void exit_io_context(struct task_struct *task)
 {