Re: [PATCH] f2fs: fix the assign logic of iocb

[Pavan Kondeti]

Hi Mukesh,

On Wed, Oct 19, 2022 at 09:47:57PM +0530, Mukesh Ojha wrote:
> commit 18ae8d12991b ("f2fs: show more DIO information in tracepoint")
> introduces iocb field in 'f2fs_direct_IO_enter' trace event
> And it only assigns the pointer and later it accesses its field
> in trace print log.
> 
> Fix it by correcting data type and memcpy the content of iocb.
> 
> Fixes: 18ae8d12991b ("f2fs: show more DIO information in tracepoint")
> Signed-off-by: Mukesh Ojha <quic_mojha@xxxxxxxxxxx>
> ---
>  include/trace/events/f2fs.h | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> index c6b3724..7727ec9 100644
> --- a/include/trace/events/f2fs.h
> +++ b/include/trace/events/f2fs.h
> @@ -940,7 +940,7 @@ TRACE_EVENT(f2fs_direct_IO_enter,
>  	TP_STRUCT__entry(
>  		__field(dev_t,	dev)
>  		__field(ino_t,	ino)
> -		__field(struct kiocb *,	iocb)
> +		__field_struct(struct kiocb,	iocb)
>  		__field(unsigned long,	len)
>  		__field(int,	rw)
>  	),
> @@ -948,17 +948,17 @@ TRACE_EVENT(f2fs_direct_IO_enter,
>  	TP_fast_assign(
>  		__entry->dev	= inode->i_sb->s_dev;
>  		__entry->ino	= inode->i_ino;
> -		__entry->iocb	= iocb;
> +		 memcpy(&__entry->iocb, iocb, sizeof(*iocb));
>  		__entry->len	= len;
>  		__entry->rw	= rw;
>  	),
>  

Why copy the whole structure (48 bytes)? cache the three members you
need.

Thanks,
Pavan