samples: bpf: Fix broken bpf programs due to removed symbol

>From commit f1394b79 ("block: mark blk_account_io_completion
static") symbol blk_account_io_completion() has been marked as static,
which makes it no longer possible to attach kprobe to this event.
Currently, there are broken samples due to this reason.

As a solution to this, attach kprobe events to blk_account_io_done()
to modify them to perform the same behavior as before.
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200818051641.21724-1-danieltimlee@gmail.com

samples/bpf/task_fd_query_kern.c

@@ -10,7 +10,7 @@ int bpf_prog1(struct pt_regs *ctx)
 	return 0;
 }
 
-SEC("kretprobe/blk_account_io_completion")
+SEC("kretprobe/blk_account_io_done")
 int bpf_prog2(struct pt_regs *ctx)
 {
 	return 0;

samples/bpf/task_fd_query_user.c

@@ -314,7 +314,7 @@ int main(int argc, char **argv)
 	/* test two functions in the corresponding *_kern.c file */
 	CHECK_AND_RET(test_debug_fs_kprobe(0, "blk_mq_start_request",
 					   BPF_FD_TYPE_KPROBE));
-	CHECK_AND_RET(test_debug_fs_kprobe(1, "blk_account_io_completion",
+	CHECK_AND_RET(test_debug_fs_kprobe(1, "blk_account_io_done",
 					   BPF_FD_TYPE_KRETPROBE));
 
 	/* test nondebug fs kprobe */

samples/bpf/tracex3_kern.c

@@ -49,7 +49,7 @@ struct {
 	__uint(max_entries, SLOTS);
 } lat_map SEC(".maps");
 
-SEC("kprobe/blk_account_io_completion")
+SEC("kprobe/blk_account_io_done")
 int bpf_prog2(struct pt_regs *ctx)
 {
 	long rq = PT_REGS_PARM1(ctx);