linux-kernel - Re: [PATCH 1/1] ftrace: fix wrong pos computing when read buffer has been fulfilled.

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Date:	Tue, 18 Nov 2008 09:36:07 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	walimis <walimisdev@...il.com>
cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] ftrace: fix wrong pos computing when read buffer
 has been fulfilled.


On Sat, 15 Nov 2008, walimis wrote:

> 
> hi Steven,
> 
> Could you help me to review this patch?
> 
> Thanks.
> 
> Impact: make output of available_filter_functions complete
> 
> phenomenon:
> 
> The first value of dyn_ftrace_total_info is not equal with
> `cat available_filter_functions | wc -l`, but they should be equal.
> 
> root cause:
> 
> When printing functions with seq_printf in t_show, if the read buffer
> is just overflowed by current function record, then this function
> won't be printed to user space through read buffer, it will
> just be dropped. So we can't see this function printing.
> So, every time the last function to fill the read buffer, if overflowed,
> will be dropped.
> This also applies to set_ftrace_filter if set_ftrace_filter has
> more bytes than read buffer.
> 
> fix:
> 
> Through checking return value of seq_printf, if less than 0, we know
> this function doesn't be printed. Then we decrease position to force
> this function to be printed next time, in next read buffer.

A lot of the code for seq files I cut and paste from other places that I 
have written it. The seq files always confuse me, so I like to use stuff 
that worked before. Some of the things that walimis fixed were not needed 
for this file, and was overkill.

> 
> another little fix is to show correct allocating pages count.

Ack.

> 
> Signed-off-by: walimis <walimisdev@...il.com>

Acked-by: Steven Rostedt <srostedt@...hat.com>

-- Steve

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