linux-kernel - Re: [PATCH v8 08/12] user_events: Optimize writing events by only copying data once

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Message-ID: <20220106171745.1496c723@gandalf.local.home>
Date:   Thu, 6 Jan 2022 17:17:45 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Beau Belgrave <beaub@...ux.microsoft.com>
Cc:     mhiramat@...nel.org, linux-trace-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 08/12] user_events: Optimize writing events by only
 copying data once

On Thu, 16 Dec 2021 09:35:07 -0800
Beau Belgrave <beaub@...ux.microsoft.com> wrote:

> @@ -1018,16 +1081,11 @@ static ssize_t user_events_write_core(struct file *file, struct iov_iter *i)
>  	if (likely(atomic_read(&tp->key.enabled) > 0)) {
>  		struct tracepoint_func *probe_func_ptr;
>  		user_event_func_t probe_func;
> +		struct iov_iter copy;
>  		void *tpdata;
> -		void *kdata;
> -		u32 datalen;
> -
> -		kdata = kmalloc(i->count, GFP_KERNEL);
>  
> -		if (unlikely(!kdata))
> -			return -ENOMEM;
> -
> -		datalen = copy_from_iter(kdata, i->count, i);
> +		if (unlikely(iov_iter_fault_in_readable(i, i->count)))

Can you rebase on my tree: ftrace/core ?

That's because upstream now has:

a6294593e8a12 ("iov_iter: Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable")

And it looks like you need to call fault_in_iov_iter_readable().

-- Steve


> +			return -EFAULT;
>  
>  		rcu_read_lock_sched();
>