[PATCH] samples: bpf: fix: broken sample regarding removed function

[PATCH] samples: bpf: fix: broken sample regarding removed function

[Daniel T. Lee]

Currently, running sample "task_fd_query" and "tracex3" occurs the
following error. On kernel v5.0-rc* this sample will be unavailable
due to the removal of function 'blk_start_request' at commit "a1ce35f".
(function removed, as "Single Queue IO scheduler" no longer exists)

$ sudo ./task_fd_query
failed to create kprobe 'blk_start_request' error 'No such file or
directory'

This commit will change the function 'blk_start_request' to
'blk_mq_start_request' to fix the broken sample.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
 samples/bpf/task_fd_query_kern.c | 2 +-
 samples/bpf/task_fd_query_user.c | 2 +-
 samples/bpf/tracex3_kern.c       | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/samples/bpf/task_fd_query_kern.c b/samples/bpf/task_fd_query_kern.c
index f4b0a9ea674d..5f1b2cdababd 100644
--- a/samples/bpf/task_fd_query_kern.c
+++ b/samples/bpf/task_fd_query_kern.c
@@ -4,7 +4,7 @@
 #include <uapi/linux/bpf.h>
 #include "bpf_helpers.h"
 
-SEC("kprobe/blk_start_request")
+SEC("kprobe/blk_mq_start_requset")
 int bpf_prog1(struct pt_regs *ctx)
 {
 	return 0;
diff --git a/samples/bpf/task_fd_query_user.c b/samples/bpf/task_fd_query_user.c
index 8381d792f138..a6e6c76e50c9 100644
--- a/samples/bpf/task_fd_query_user.c
+++ b/samples/bpf/task_fd_query_user.c
@@ -311,7 +311,7 @@ int main(int argc, char **argv)
 	}
 
 	/* test two functions in the corresponding *_kern.c file */
-	CHECK_AND_RET(test_debug_fs_kprobe(0, "blk_start_request",
+	CHECK_AND_RET(test_debug_fs_kprobe(0, "blk_mq_start_requset",
 					   BPF_FD_TYPE_KPROBE));
 	CHECK_AND_RET(test_debug_fs_kprobe(1, "blk_account_io_completion",
 					   BPF_FD_TYPE_KRETPROBE));
diff --git a/samples/bpf/tracex3_kern.c b/samples/bpf/tracex3_kern.c
index 9974c3d7c18b..4378492a970a 100644
--- a/samples/bpf/tracex3_kern.c
+++ b/samples/bpf/tracex3_kern.c
@@ -20,7 +20,7 @@ struct bpf_map_def SEC("maps") my_map = {
 /* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
  * example will no longer be meaningful
  */
-SEC("kprobe/blk_start_request")
+SEC("kprobe/blk_mq_start_requset")
 int bpf_prog1(struct pt_regs *ctx)
 {
 	long rq = PT_REGS_PARM1(ctx);
-- 
2.17.1

Re: [PATCH] samples: bpf: fix: broken sample regarding removed function

[Martin Lau]

On Tue, Feb 26, 2019 at 10:05:59PM -0500, Daniel T. Lee wrote:
> Currently, running sample "task_fd_query" and "tracex3" occurs the
> following error. On kernel v5.0-rc* this sample will be unavailable
> due to the removal of function 'blk_start_request' at commit "a1ce35f".
> (function removed, as "Single Queue IO scheduler" no longer exists)
> 
> $ sudo ./task_fd_query
> failed to create kprobe 'blk_start_request' error 'No such file or
> directory'
> 
> This commit will change the function 'blk_start_request' to
> 'blk_mq_start_request' to fix the broken sample.
> 
> Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
> ---
>  samples/bpf/task_fd_query_kern.c | 2 +-
>  samples/bpf/task_fd_query_user.c | 2 +-
>  samples/bpf/tracex3_kern.c       | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/samples/bpf/task_fd_query_kern.c b/samples/bpf/task_fd_query_kern.c
> index f4b0a9ea674d..5f1b2cdababd 100644
> --- a/samples/bpf/task_fd_query_kern.c
> +++ b/samples/bpf/task_fd_query_kern.c
> @@ -4,7 +4,7 @@
>  #include <uapi/linux/bpf.h>
>  #include "bpf_helpers.h"
>  
> -SEC("kprobe/blk_start_request")
> +SEC("kprobe/blk_mq_start_requset")
I suspect it does not run.  Have you tested it?

There is a typo:
blk_mq_start_requSEt
blk_mq_start_requESt