Re: [PATCH v2 09/15] blktrace: add definitions for struct blk_io_trace2

Damien Le Moal
2025-10-01T06:37:16Z

On 9/26/25 00:02, Johannes Thumshirn wrote:
> Add definitions for the extended version of the blktrace protocol using a
> wider action type to be able to record new actions in the kernel.
>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
> include/uapi/linux/blktrace_api.h | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/include/uapi/linux/blktrace_api.h b/include/uapi/linux/blktrace_api.h
> index a3b1f35ac026..d58ef484de49 100644
> --- a/include/uapi/linux/blktrace_api.h
> +++ b/include/uapi/linux/blktrace_api.h
> @@ -94,6 +94,7 @@ enum blktrace_notify {
>
> #define BLK_IO_TRACE_MAGIC 0x65617400
> #define BLK_IO_TRACE_VERSION 0x07
> +#define BLK_IO_TRACE2_VERSION 0x08
>
> /*
> * The trace itself
> @@ -113,6 +114,21 @@ struct blk_io_trace {
> /* cgroup id will be stored here if exists */
> };
>
> +struct blk_io_trace2 {
> + __u32 magic; /* MAGIC << 8 | BLK_IO_TRACE2_VERSION */
> + __u32 sequence; /* event number */
> + __u64 time; /* in nanoseconds */
> + __u64 sector; /* disk offset */
> + __u32 bytes; /* transfer length */
> + __u32 pid; /* who did it */
> + __u64 action; /* what happened */
> + __u32 device; /* device number */
> + __u32 cpu; /* on what cpu did it happen */
> + __u16 error; /* completion error */
> + __u16 pdu_len; /* length of data after this trace */
> + __u8 pad[8];

Why 8 ? that makes the structure 4B 60 B. Padding to 12 would make it nicely
aligned to 64B...

> + /* cgroup id will be stored here if exists */
> +};
> /*
> * The remap event
> */

--
Damien Le Moal
Western Digital Research