linux-kernel - Re: [RFC][PATCH 14/23 v4] tracing: Convert seq_buf_path() to be like seq

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Date:	Fri, 14 Nov 2014 17:53:08 +0100
From:	Petr Mladek <pmladek@...e.cz>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>
Subject: Re: [RFC][PATCH 14/23 v4] tracing: Convert seq_buf_path() to be like
 seq_path()

On Thu 2014-11-13 20:12:58, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
> 
> Rewrite seq_buf_path() like it is done in seq_path() and allow
> it to accept any escape character instead of just "\n".
> 
> Making seq_buf_path() like seq_path() will help prevent problems
> when converting seq_file to use the seq_buf logic.
> 
> Link: http://lkml.kernel.org/r/20141104160222.048795666@goodmis.org
> 
> Tested-by: Jiri Kosina <jkosina@...e.cz>
> Acked-by: Jiri Kosina <jkosina@...e.cz>
> Reviewed-by: Petr Mladek <pmladek@...e.cz>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  include/linux/seq_buf.h  |  2 +-
>  kernel/trace/seq_buf.c   | 28 ++++++++++++++++------------
>  kernel/trace/trace_seq.c |  4 ++--
>  3 files changed, 19 insertions(+), 15 deletions(-)
> 
> diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
> index 4f7a96a9d71a..38770688a627 100644
> --- a/include/linux/seq_buf.h
> +++ b/include/linux/seq_buf.h
> @@ -73,7 +73,7 @@ extern int seq_buf_putc(struct seq_buf *s, unsigned char c);
>  extern int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len);
>  extern int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
>  			      unsigned int len);
> -extern int seq_buf_path(struct seq_buf *s, const struct path *path);
> +extern int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc);
>  
>  extern int seq_buf_bitmask(struct seq_buf *s, const unsigned long *maskp,
>  			   int nmaskbits);
> diff --git a/kernel/trace/seq_buf.c b/kernel/trace/seq_buf.c
> index e9a7861595d2..7dac34d1235b 100644
> --- a/kernel/trace/seq_buf.c
> +++ b/kernel/trace/seq_buf.c
> @@ -272,28 +272,32 @@ int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
>   * seq_buf_path - copy a path into the sequence buffer
>   * @s: seq_buf descriptor
>   * @path: path to write into the sequence buffer.
> + * @esc: set of characters to escape in the output
>   *
>   * Write a path name into the sequence buffer.
>   *
> - * Returns zero on success, -1 on overflow
> + * Returns the number of written bytes on success, -1 on overflow
>   */
> -int seq_buf_path(struct seq_buf *s, const struct path *path)
> +int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
>  {
> -	unsigned int len = seq_buf_buffer_left(s);
> -	unsigned char *p;
> +	char *buf = s->buffer + s->len;
> +	size_t size = seq_buf_buffer_left(s);
> +	int res = -1;
>  
>  	WARN_ON(s->size == 0);
>  
> -	p = d_path(path, s->buffer + s->len, len);
> -	if (!IS_ERR(p)) {
> -		p = mangle_path(s->buffer + s->len, p, "\n");
> -		if (p) {
> -			s->len = p - s->buffer;
> -			return 0;
> +	if (size) {
> +		char *p = d_path(path, buf, size);
> +		if (!IS_ERR(p)) {
> +			char *end = mangle_path(buf, p, esc);
> +			if (end)
> +				res = end - buf;
>  		}
>  	}
> -	seq_buf_set_overflow(s);
> -	return -1;
> +	if (res > 0)
> +		s->len += res;
> +
> +	return res;
>  }
>  
>  /**
> diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c
> index 3c63b619d6b7..475412e31de5 100644
> --- a/kernel/trace/trace_seq.c
> +++ b/kernel/trace/trace_seq.c
> @@ -342,7 +342,7 @@ int trace_seq_path(struct trace_seq *s, const struct path *path)
>  		return 0;
>  	}
>  
> -	ret = seq_buf_path(&s->seq, path);
> +	ret = seq_buf_path(&s->seq, path, "\n");
>  
>  	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
>  		s->seq.len = save_len;
> @@ -350,7 +350,7 @@ int trace_seq_path(struct trace_seq *s, const struct path *path)
>  		return 0;
>  	}
>  
> -	return ret;
> +	return 1;

Ah, I have just realized that this should return -1 when
seq_buf_path() returns -1.

Note that set_buf_path() does not longer calls seq_buf_set_overflow(s)
when the path handling fails. Therefore the above check for overflow
will probably never happen.

Best Regards,
Petr

>  }
>  EXPORT_SYMBOL_GPL(trace_seq_path);
>  
> -- 
> 2.1.1
> 
> 
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