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SubjectRe: [PATCH v2][GIT PULL][v2.6.35] tracing/events: Convert format output to seq_file
Steven Rostedt wrote:
> Ingo,
>
> Please pull the latest tip/perf/urgent-2 tree, which can be found at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
> tip/perf/urgent-2
>
>
> Steven Rostedt (1):
> tracing/events: Convert format output to seq_file
>
> ----
> kernel/trace/trace_events.c | 208 +++++++++++++++++++++++++++++--------------
> 1 files changed, 141 insertions(+), 67 deletions(-)
> ---------------------------
> commit bcaa10360f3b2a623453a9fb10ef77aafeef8bb6
> Author: Steven Rostedt <srostedt@redhat.com>
> Date: Thu Jun 3 15:21:34 2010 -0400
>
> tracing/events: Convert format output to seq_file
>
> Two new events were added that broke the current format output.
>
> Both from the SCSI system: scsi_dispatch_cmd_done and scsi_dispatch_cmd_timeout
>
> The reason is that their print_fmt exceeded a page size. Since the output
> of the format used simple_read_from_buffer and trace_seq, it was limited
> to a page size in output.
>
> This patch converts the printing of the format of an event into seq_file,
> which allows greater than a page size to be shown.
>
> I diffed all event formats comparing the output with and without this
> patch. All matched except for the above two, which showed just:
>
> FORMAT TOO BIG
>
> without this patch, but now properly displays the output with this patch.
>
> v2: Remove updating *pos in seq start function.
> [ Thanks to Li Zefan for pointing that out ]

There's been an oversight... Thanks a lot for finding and fixing
this! I built a kernel with the patch applied and confirmed the
issue is fixed on my box.

Tested-by: Kei Tokunaga <tokunaga.keiich@jp.fujitsu.com>

> Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: Kei Tokunaga <tokunaga.keiich@jp.fujitsu.com>
> Cc: James Bottomley <James.Bottomley@suse.de>
> Cc: Tomohiro Kusumi <kusumi.tomohiro@jp.fujitsu.com>
> Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
>
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 53cffc0..45a8968 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -29,6 +29,8 @@ DEFINE_MUTEX(event_mutex);
>
> LIST_HEAD(ftrace_events);
>
> +#define COMMON_FIELD_COUNT 5
> +
> struct list_head *
> trace_get_fields(struct ftrace_event_call *event_call)
> {
> @@ -544,85 +546,155 @@ out:
> return ret;
> }
>
> -static ssize_t
> -event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
> - loff_t *ppos)
> +enum {
> + FORMAT_HEADER = 1,
> + FORMAT_PRINTFMT = 2,
> +};
> +
> +static void *f_next(struct seq_file *m, void *v, loff_t *pos)
> {
> - struct ftrace_event_call *call = filp->private_data;
> + struct ftrace_event_call *call = m->private;
> struct ftrace_event_field *field;
> struct list_head *head;
> - struct trace_seq *s;
> - int common_field_count = 5;
> - char *buf;
> - int r = 0;
> -
> - if (*ppos)
> - return 0;
> + loff_t index = *pos;
>
> - s = kmalloc(sizeof(*s), GFP_KERNEL);
> - if (!s)
> - return -ENOMEM;
> + (*pos)++;
>
> - trace_seq_init(s);
> + head = trace_get_fields(call);
>
> - trace_seq_printf(s, "name: %s\n", call->name);
> - trace_seq_printf(s, "ID: %d\n", call->event.type);
> - trace_seq_printf(s, "format:\n");
> + switch ((unsigned long)v) {
> + case FORMAT_HEADER:
>
> - head = trace_get_fields(call);
> - list_for_each_entry_reverse(field, head, link) {
> - /*
> - * Smartly shows the array type(except dynamic array).
> - * Normal:
> - * field:TYPE VAR
> - * If TYPE := TYPE[LEN], it is shown:
> - * field:TYPE VAR[LEN]
> - */
> - const char *array_descriptor = strchr(field->type, '[');
> -
> - if (!strncmp(field->type, "__data_loc", 10))
> - array_descriptor = NULL;
> -
> - if (!array_descriptor) {
> - r = trace_seq_printf(s, "\tfield:%s %s;\toffset:%u;"
> - "\tsize:%u;\tsigned:%d;\n",
> - field->type, field->name, field->offset,
> - field->size, !!field->is_signed);
> - } else {
> - r = trace_seq_printf(s, "\tfield:%.*s %s%s;\toffset:%u;"
> - "\tsize:%u;\tsigned:%d;\n",
> - (int)(array_descriptor - field->type),
> - field->type, field->name,
> - array_descriptor, field->offset,
> - field->size, !!field->is_signed);
> - }
> + if (unlikely(list_empty(head)))
> + return NULL;
>
> - if (--common_field_count == 0)
> - r = trace_seq_printf(s, "\n");
> + field = list_entry(head->prev, struct ftrace_event_field, link);
> + return field;
>
> - if (!r)
> - break;
> + case FORMAT_PRINTFMT:
> + /* all done */
> + return NULL;
> }
>
> - if (r)
> - r = trace_seq_printf(s, "\nprint fmt: %s\n",
> - call->print_fmt);
> + /*
> + * To separate common fields from event fields, the
> + * LSB is set on the first event field. Clear it in case.
> + */
> + v = (void *)((unsigned long)v & ~1L);
>
> - if (!r) {
> - /*
> - * ug! The format output is bigger than a PAGE!!
> - */
> - buf = "FORMAT TOO BIG\n";
> - r = simple_read_from_buffer(ubuf, cnt, ppos,
> - buf, strlen(buf));
> - goto out;
> + field = v;
> + if (field->link.prev == head)
> + return (void *)FORMAT_PRINTFMT;
> +
> + field = list_entry(field->link.prev, struct ftrace_event_field, link);
> +
> + /* Set the LSB to notify f_show to print an extra newline */
> + if (index == COMMON_FIELD_COUNT)
> + field = (struct ftrace_event_field *)
> + ((unsigned long)field | 1);
> +
> + return field;
> +}
> +
> +static void *f_start(struct seq_file *m, loff_t *pos)
> +{
> + loff_t l = 0;
> + void *p;
> +
> + /* Start by showing the header */
> + if (!*pos)
> + return (void *)FORMAT_HEADER;
> +
> + p = (void *)FORMAT_HEADER;
> + do {
> + p = f_next(m, p, &l);
> + } while (p && l < *pos);
> +
> + return p;
> +}
> +
> +static int f_show(struct seq_file *m, void *v)
> +{
> + struct ftrace_event_call *call = m->private;
> + struct ftrace_event_field *field;
> + const char *array_descriptor;
> +
> + switch ((unsigned long)v) {
> + case FORMAT_HEADER:
> + seq_printf(m, "name: %s\n", call->name);
> + seq_printf(m, "ID: %d\n", call->event.type);
> + seq_printf(m, "format:\n");
> + return 0;
> +
> + case FORMAT_PRINTFMT:
> + seq_printf(m, "\nprint fmt: %s\n",
> + call->print_fmt);
> + return 0;
> }
>
> - r = simple_read_from_buffer(ubuf, cnt, ppos,
> - s->buffer, s->len);
> - out:
> - kfree(s);
> - return r;
> + /*
> + * To separate common fields from event fields, the
> + * LSB is set on the first event field. Clear it and
> + * print a newline if it is set.
> + */
> + if ((unsigned long)v & 1) {
> + seq_putc(m, '\n');
> + v = (void *)((unsigned long)v & ~1L);
> + }
> +
> + field = v;
> +
> + /*
> + * Smartly shows the array type(except dynamic array).
> + * Normal:
> + * field:TYPE VAR
> + * If TYPE := TYPE[LEN], it is shown:
> + * field:TYPE VAR[LEN]
> + */
> + array_descriptor = strchr(field->type, '[');
> +
> + if (!strncmp(field->type, "__data_loc", 10))
> + array_descriptor = NULL;
> +
> + if (!array_descriptor)
> + seq_printf(m, "\tfield:%s %s;\toffset:%u;\tsize:%u;\tsigned:%d;\n",
> + field->type, field->name, field->offset,
> + field->size, !!field->is_signed);
> + else
> + seq_printf(m, "\tfield:%.*s %s%s;\toffset:%u;\tsize:%u;\tsigned:%d;\n",
> + (int)(array_descriptor - field->type),
> + field->type, field->name,
> + array_descriptor, field->offset,
> + field->size, !!field->is_signed);
> +
> + return 0;
> +}
> +
> +static void f_stop(struct seq_file *m, void *p)
> +{
> +}
> +
> +static const struct seq_operations trace_format_seq_ops = {
> + .start = f_start,
> + .next = f_next,
> + .stop = f_stop,
> + .show = f_show,
> +};
> +
> +static int trace_format_open(struct inode *inode, struct file *file)
> +{
> + struct ftrace_event_call *call = inode->i_private;
> + struct seq_file *m;
> + int ret;
> +
> + ret = seq_open(file, &trace_format_seq_ops);
> + if (ret < 0)
> + return ret;
> +
> + m = file->private_data;
> + m->private = call;
> +
> + return 0;
> }
>
> static ssize_t
> @@ -820,8 +892,10 @@ static const struct file_operations ftrace_enable_fops = {
> };
>
> static const struct file_operations ftrace_event_format_fops = {
> - .open = tracing_open_generic,
> - .read = event_format_read,
> + .open = trace_format_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = seq_release,
> };
>
> static const struct file_operations ftrace_event_id_fops = {
>
>
>
>



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