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    Subject[PATCH 07/13] tracing: Use seq file for trace_options
    Date
    From: Li Zefan <lizf@cn.fujitsu.com>

    Code simplification for reading trace_options.

    Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
    Acked-by: Steven Rostedt <rostedt@goodmis.org>
    LKML-reference: <4B1DC4EF.3090106@cn.fujitsu.com>
    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    ---
    kernel/trace/trace.c | 60 ++++++++++++++-----------------------------------
    1 files changed, 17 insertions(+), 43 deletions(-)

    diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
    index 88bd9ae..a6c41cc 100644
    --- a/kernel/trace/trace.c
    +++ b/kernel/trace/trace.c
    @@ -2316,67 +2316,32 @@ static const struct file_operations tracing_cpumask_fops = {
    .write = tracing_cpumask_write,
    };

    -static ssize_t
    -tracing_trace_options_read(struct file *filp, char __user *ubuf,
    - size_t cnt, loff_t *ppos)
    +static int tracing_trace_options_show(struct seq_file *m, void *v)
    {
    struct tracer_opt *trace_opts;
    u32 tracer_flags;
    - int len = 0;
    - char *buf;
    - int r = 0;
    int i;

    -
    - /* calculate max size */
    - for (i = 0; trace_options[i]; i++) {
    - len += strlen(trace_options[i]);
    - len += 3; /* "no" and newline */
    - }
    -
    mutex_lock(&trace_types_lock);
    tracer_flags = current_trace->flags->val;
    trace_opts = current_trace->flags->opts;

    - /*
    - * Increase the size with names of options specific
    - * of the current tracer.
    - */
    - for (i = 0; trace_opts[i].name; i++) {
    - len += strlen(trace_opts[i].name);
    - len += 3; /* "no" and newline */
    - }
    -
    - /* +1 for \0 */
    - buf = kmalloc(len + 1, GFP_KERNEL);
    - if (!buf) {
    - mutex_unlock(&trace_types_lock);
    - return -ENOMEM;
    - }
    -
    for (i = 0; trace_options[i]; i++) {
    if (trace_flags & (1 << i))
    - r += sprintf(buf + r, "%s\n", trace_options[i]);
    + seq_printf(m, "%s\n", trace_options[i]);
    else
    - r += sprintf(buf + r, "no%s\n", trace_options[i]);
    + seq_printf(m, "no%s\n", trace_options[i]);
    }

    for (i = 0; trace_opts[i].name; i++) {
    if (tracer_flags & trace_opts[i].bit)
    - r += sprintf(buf + r, "%s\n",
    - trace_opts[i].name);
    + seq_printf(m, "%s\n", trace_opts[i].name);
    else
    - r += sprintf(buf + r, "no%s\n",
    - trace_opts[i].name);
    + seq_printf(m, "no%s\n", trace_opts[i].name);
    }
    mutex_unlock(&trace_types_lock);

    - WARN_ON(r >= len + 1);
    -
    - r = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
    -
    - kfree(buf);
    - return r;
    + return 0;
    }

    /* Try to assign a tracer specific option */
    @@ -2471,9 +2436,18 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
    return cnt;
    }

    +static int tracing_trace_options_open(struct inode *inode, struct file *file)
    +{
    + if (tracing_disabled)
    + return -ENODEV;
    + return single_open(file, tracing_trace_options_show, NULL);
    +}
    +
    static const struct file_operations tracing_iter_fops = {
    - .open = tracing_open_generic,
    - .read = tracing_trace_options_read,
    + .open = tracing_trace_options_open,
    + .read = seq_read,
    + .llseek = seq_lseek,
    + .release = single_release,
    .write = tracing_trace_options_write,
    };

    --
    1.6.2.3


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