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SubjectRe: [PATCH] tracing/filters: Improve subsystem filter
On Thu, Jul 16, 2009 at 05:03:24PM +0800, Li Zefan wrote:
> Currently a subsystem filter should be applicable to all events
> under the subsystem, and if it failed, all the event filters
> will be cleared. Those behaviors make subsys filter much less
> useful:
>
> # echo 'vec == 1' > irq/softirq_entry/filter
> # echo 'irq == 5' > irq/filter
> bash: echo: write error: Invalid argument
> # cat irq/softirq_entry/filter
> none
>
> I'd expect it set the filter for irq_handler_entry/exit, and
> not touch softirq_entry/exit.
>
> The basic idea is, try to see if the filter can be applied
> to which events, and then just apply to the those events:
>
> # echo 'vec == 1' > softirq_entry/filter
> # echo 'irq == 5' > filter
> # cat irq_handler_entry/filter
> irq == 5
> # cat softirq_entry/filter
> vec == 1
>
> Inspied-by: Steven Rostedt <srostedt@redhat.com>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> ---
> include/linux/ftrace_event.h | 4 +-
> kernel/trace/trace.h | 3 +-
> kernel/trace/trace_events_filter.c | 123 +++++++++++++++++++++++------------
> 3 files changed, 86 insertions(+), 44 deletions(-)
>
> diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
> index 5c093ff..26d3673 100644
> --- a/include/linux/ftrace_event.h
> +++ b/include/linux/ftrace_event.h
> @@ -101,6 +101,8 @@ void trace_current_buffer_discard_commit(struct ring_buffer_event *event);
>
> void tracing_record_cmdline(struct task_struct *tsk);
>
> +struct event_filter;
> +
> struct ftrace_event_call {
> struct list_head list;
> char *name;
> @@ -116,7 +118,7 @@ struct ftrace_event_call {
> int (*define_fields)(void);
> struct list_head fields;
> int filter_active;
> - void *filter;
> + struct event_filter *filter;
> void *mod;
>
> #ifdef CONFIG_EVENT_PROFILE
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 06886a0..3a87d46 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -768,13 +768,14 @@ struct event_filter {
> int n_preds;
> struct filter_pred **preds;
> char *filter_string;
> + bool no_reset;
> };
>
> struct event_subsystem {
> struct list_head list;
> const char *name;
> struct dentry *entry;
> - void *filter;
> + struct event_filter *filter;
> int nr_events;
> };
>
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index 1c80ef7..0f510c2 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -420,7 +420,13 @@ oom:
> }
> EXPORT_SYMBOL_GPL(init_preds);
>
> -static void filter_free_subsystem_preds(struct event_subsystem *system)
> +/*
> + * flag == 0: remove all events' filter
> + * flag == 1: clear filter->no_reset
> + * flag == 2: remove all preds with no_reset == false
> + */



Once an option overlap the boolean binary range, it's better
to start thinking about an enum type, for better self-explaining code.


> +static void filter_free_subsystem_preds(struct event_subsystem *system,
> + int flag)
> {
> struct ftrace_event_call *call;
>
> @@ -428,6 +434,14 @@ static void filter_free_subsystem_preds(struct event_subsystem *system)
> if (!call->define_fields)
> continue;
>
> + if (flag == 1) {
> + call->filter->no_reset = false;
> + continue;
> + }
> +
> + if (flag == 2 && call->filter->no_reset == true)



Or simply if (flag == 2 && call->filter->no_reset)



> + continue;
> +
> if (!strcmp(call->system, system->name)) {
> filter_disable_preds(call);
> remove_filter_string(call->filter);
> @@ -529,7 +543,8 @@ static filter_pred_fn_t select_comparison_fn(int op, int field_size,
>
> static int filter_add_pred(struct filter_parse_state *ps,
> struct ftrace_event_call *call,
> - struct filter_pred *pred)
> + struct filter_pred *pred,
> + bool apply)


bool dry_run sounds perhaps more intuitive for what is happening there.
Because "apply" is surprising in a "add_thing" function, it's like
a field to confirm that we know what what we are doing :)

(May be I start to become a PITA with my naming worries, especially
since I'm usually not good at it in my patches :)

Otherwise, the rest looks good.

Tom, any comment?


> {
> struct ftrace_event_field *field;
> filter_pred_fn_t fn;
> @@ -541,10 +556,12 @@ static int filter_add_pred(struct filter_parse_state *ps,
>
> if (pred->op == OP_AND) {
> pred->pop_n = 2;
> - return filter_add_pred_fn(ps, call, pred, filter_pred_and);
> + fn = filter_pred_and;
> + goto add_pred_fn;
> } else if (pred->op == OP_OR) {
> pred->pop_n = 2;
> - return filter_add_pred_fn(ps, call, pred, filter_pred_or);
> + fn = filter_pred_or;
> + goto add_pred_fn;
> }
>
> field = find_event_field(call, pred->field_name);
> @@ -567,9 +584,6 @@ static int filter_add_pred(struct filter_parse_state *ps,
> else
> fn = filter_pred_strloc;
> pred->str_len = field->size;
> - if (pred->op == OP_NE)
> - pred->not = 1;
> - return filter_add_pred_fn(ps, call, pred, fn);
> } else {
> if (field->is_signed)
> ret = strict_strtoll(pred->str_val, 0, &val);
> @@ -580,27 +594,33 @@ static int filter_add_pred(struct filter_parse_state *ps,
> return -EINVAL;
> }
> pred->val = val;
> - }
>
> - fn = select_comparison_fn(pred->op, field->size, field->is_signed);
> - if (!fn) {
> - parse_error(ps, FILT_ERR_INVALID_OP, 0);
> - return -EINVAL;
> + fn = select_comparison_fn(pred->op, field->size,
> + field->is_signed);
> + if (!fn) {
> + parse_error(ps, FILT_ERR_INVALID_OP, 0);
> + return -EINVAL;
> + }
> }
>
> if (pred->op == OP_NE)
> pred->not = 1;
>
> - return filter_add_pred_fn(ps, call, pred, fn);
> +add_pred_fn:
> + if (apply)
> + return filter_add_pred_fn(ps, call, pred, fn);
> + return 0;
> }
>
> static int filter_add_subsystem_pred(struct filter_parse_state *ps,
> struct event_subsystem *system,
> struct filter_pred *pred,
> - char *filter_string)
> + char *filter_string,
> + bool apply)
> {
> struct ftrace_event_call *call;
> int err = 0;
> + bool fail = true;
>
> list_for_each_entry(call, &ftrace_events, list) {
>
> @@ -610,16 +630,24 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
> if (strcmp(call->system, system->name))
> continue;
>
> - err = filter_add_pred(ps, call, pred);
> - if (err) {
> - filter_free_subsystem_preds(system);
> - parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
> - goto out;
> - }
> - replace_filter_string(call->filter, filter_string);
> + if (call->filter->no_reset)
> + continue;
> +
> + err = filter_add_pred(ps, call, pred, apply);
> + if (err)
> + call->filter->no_reset = true;
> + else
> + fail = false;
> +
> + if (apply)
> + replace_filter_string(call->filter, filter_string);
> }
> -out:
> - return err;
> +
> + if (fail) {
> + parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
> + return err;
> + }
> + return 0;
> }
>
> static void parse_init(struct filter_parse_state *ps,
> @@ -978,12 +1006,14 @@ static int check_preds(struct filter_parse_state *ps)
> static int replace_preds(struct event_subsystem *system,
> struct ftrace_event_call *call,
> struct filter_parse_state *ps,
> - char *filter_string)
> + char *filter_string,
> + bool apply)
> {
> char *operand1 = NULL, *operand2 = NULL;
> struct filter_pred *pred;
> struct postfix_elt *elt;
> int err;
> + int n_preds = 0;
>
> err = check_preds(ps);
> if (err)
> @@ -1002,19 +1032,14 @@ static int replace_preds(struct event_subsystem *system,
> continue;
> }
>
> + if (n_preds++ == MAX_FILTER_PRED) {
> + parse_error(ps, FILT_ERR_TOO_MANY_PREDS, 0);
> + return -ENOSPC;
> + }
> +
> if (elt->op == OP_AND || elt->op == OP_OR) {
> pred = create_logical_pred(elt->op);
> - if (call)
> - err = filter_add_pred(ps, call, pred);
> - else
> - err = filter_add_subsystem_pred(ps, system,
> - pred, filter_string);
> - filter_free_pred(pred);
> - if (err)
> - return err;
> -
> - operand1 = operand2 = NULL;
> - continue;
> + goto add_pred;
> }
>
> if (!operand1 || !operand2) {
> @@ -1023,11 +1048,12 @@ static int replace_preds(struct event_subsystem *system,
> }
>
> pred = create_pred(elt->op, operand1, operand2);
> +add_pred:
> if (call)
> - err = filter_add_pred(ps, call, pred);
> + err = filter_add_pred(ps, call, pred, true);
> else
> err = filter_add_subsystem_pred(ps, system, pred,
> - filter_string);
> + filter_string, apply);
> filter_free_pred(pred);
> if (err)
> return err;
> @@ -1068,7 +1094,7 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
> goto out;
> }
>
> - err = replace_preds(NULL, call, ps, filter_string);
> + err = replace_preds(NULL, call, ps, filter_string, true);
> if (err)
> append_filter_err(ps, call->filter);
>
> @@ -1092,7 +1118,7 @@ int apply_subsystem_event_filter(struct event_subsystem *system,
> mutex_lock(&event_mutex);
>
> if (!strcmp(strstrip(filter_string), "0")) {
> - filter_free_subsystem_preds(system);
> + filter_free_subsystem_preds(system, 0);
> remove_filter_string(system->filter);
> mutex_unlock(&event_mutex);
> return 0;
> @@ -1103,7 +1129,6 @@ int apply_subsystem_event_filter(struct event_subsystem *system,
> if (!ps)
> goto out_unlock;
>
> - filter_free_subsystem_preds(system);
> replace_filter_string(system->filter, filter_string);
>
> parse_init(ps, filter_ops, filter_string);
> @@ -1113,9 +1138,23 @@ int apply_subsystem_event_filter(struct event_subsystem *system,
> goto out;
> }
>
> - err = replace_preds(system, NULL, ps, filter_string);
> - if (err)
> + filter_free_subsystem_preds(system, 1);
> +
> + /* try to see the filter can be applied to which events */
> + err = replace_preds(system, NULL, ps, filter_string, false);
> + if (err) {
> append_filter_err(ps, system->filter);
> + goto out;
> + }
> +
> + filter_free_subsystem_preds(system, 2);
> +
> + /* really apply the filter to the events */
> + err = replace_preds(system, NULL, ps, filter_string, true);
> + if (err) {
> + append_filter_err(ps, system->filter);
> + filter_free_subsystem_preds(system, 2);
> + }
>
> out:
> filter_opstack_clear(ps);
> --
> 1.6.3
>
>
>
>



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