linux-kernel - Re: [PATCH v2 1/6] tracing: add __print_flags

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Message-ID: <20161201091254.3e9f99b0@gandalf.local.home>
Date:   Thu, 1 Dec 2016 09:12:54 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Ingo Molnar <mingo@...hat.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-nvdimm@...ts.01.org
Subject: Re: [PATCH v2 1/6] tracing: add __print_flags_u64()

On Wed, 30 Nov 2016 16:45:28 -0700
Ross Zwisler <ross.zwisler@...ux.intel.com> wrote:

> Add __print_flags_u64() and the helper trace_print_flags_seq_u64() in the
> same spirit as __print_symbolic_u64() and trace_print_symbols_seq_u64().
> These functions allow us to print symbols associated with flags that are 64
> bits wide even on 32 bit machines.
> 
> These will be used by the DAX code so that we can print the flags set in a
> pfn_t such as PFN_SG_CHAIN, PFN_SG_LAST, PFN_DEV and PFN_MAP.
> 
> Without this new function I was getting errors like the following when
> compiling for i386:
> 
> ./include/linux/pfn_t.h:13:22: warning: large integer implicitly truncated
> to unsigned type [-Woverflow]
>  #define PFN_SG_CHAIN (1ULL << (BITS_PER_LONG_LONG - 1))
>   ^
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> ---
>  include/linux/trace_events.h |  4 ++++
>  include/trace/trace_events.h | 11 +++++++++++
>  kernel/trace/trace_output.c  | 38 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 53 insertions(+)
> 
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index be00761..db2c3ba 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -23,6 +23,10 @@ const char *trace_print_symbols_seq(struct trace_seq *p, unsigned long val,
>  				    const struct trace_print_flags *symbol_array);
>  
>  #if BITS_PER_LONG == 32
> +const char *trace_print_flags_seq_u64(struct trace_seq *p, const char *delim,
> +		      unsigned long long flags,
> +		      const struct trace_print_flags_u64 *flag_array);
> +
>  const char *trace_print_symbols_seq_u64(struct trace_seq *p,
>  					unsigned long long val,
>  					const struct trace_print_flags_u64
> diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
> index 467e12f..c6e9f72 100644
> --- a/include/trace/trace_events.h
> +++ b/include/trace/trace_events.h
> @@ -283,8 +283,16 @@ TRACE_MAKE_SYSTEM_STR();
>  		trace_print_symbols_seq(p, value, symbols);		\
>  	})
>  
> +#undef __print_flags_u64
>  #undef __print_symbolic_u64
>  #if BITS_PER_LONG == 32
> +#define __print_flags_u64(flag, delim, flag_array...)			\
> +	({								\
> +		static const struct trace_print_flags_u64 __flags[] =	\
> +			{ flag_array, { -1, NULL } };			\
> +		trace_print_flags_seq_u64(p, delim, flag, __flags);	\
> +	})
> +
>  #define __print_symbolic_u64(value, symbol_array...)			\
>  	({								\
>  		static const struct trace_print_flags_u64 symbols[] =	\
> @@ -292,6 +300,9 @@ TRACE_MAKE_SYSTEM_STR();
>  		trace_print_symbols_seq_u64(p, value, symbols);	\
>  	})
>  #else
> +#define __print_flags_u64(flag, delim, flag_array...)			\
> +			__print_flags(flag, delim, flag_array)
> +
>  #define __print_symbolic_u64(value, symbol_array...)			\
>  			__print_symbolic(value, symbol_array)
>  #endif
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index 3fc2042..ed4398f 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -124,6 +124,44 @@ EXPORT_SYMBOL(trace_print_symbols_seq);
>  
>  #if BITS_PER_LONG == 32
>  const char *
> +trace_print_flags_seq_u64(struct trace_seq *p, const char *delim,
> +		      unsigned long long flags,
> +		      const struct trace_print_flags_u64 *flag_array)
> +{
> +	unsigned long mask;

Don't you want mask to be unsigned long long?

-- Steve

> +	const char *str;
> +	const char *ret = trace_seq_buffer_ptr(p);
> +	int i, first = 1;
> +
> +	for (i = 0;  flag_array[i].name && flags; i++) {
> +
> +		mask = flag_array[i].mask;
> +		if ((flags & mask) != mask)
> +			continue;
> +
> +		str = flag_array[i].name;
> +		flags &= ~mask;
> +		if (!first && delim)
> +			trace_seq_puts(p, delim);
> +		else
> +			first = 0;
> +		trace_seq_puts(p, str);
> +	}
> +
> +	/* check for left over flags */
> +	if (flags) {
> +		if (!first && delim)
> +			trace_seq_puts(p, delim);
> +		trace_seq_printf(p, "0x%llx", flags);
> +	}
> +
> +	trace_seq_putc(p, 0);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(trace_print_flags_seq_u64);
> +
> +const char *
>  trace_print_symbols_seq_u64(struct trace_seq *p, unsigned long long val,
>  			 const struct trace_print_flags_u64 *symbol_array)
>  {