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    SubjectRe: [PATCH v2 1/2] tracing: Have histogram types be constant when possible
    On Thu, 22 Jul 2021 10:27:06 -0400
    Steven Rostedt <rostedt@goodmis.org> wrote:

    > From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
    >
    > Instead of kstrdup("const", GFP_KERNEL), have the hist_field type simply
    > assign the constant hist_field->type = "const"; And when the value passed
    > to it is a variable, use "kstrdup_const(var, GFP_KERNEL);" which will just
    > copy the value if the variable is already a constant. This saves on having
    > to allocate when not needed.
    >
    > All frees of the hist_field->type will need to use kfree_const().
    >

    Thanks! This looks good to me.

    Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>


    > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
    > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    > ---
    > kernel/trace/trace_events_hist.c | 32 ++++++++++++++------------------
    > 1 file changed, 14 insertions(+), 18 deletions(-)
    >
    > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
    > index 34325f41ebc0..5c9082201bc2 100644
    > --- a/kernel/trace/trace_events_hist.c
    > +++ b/kernel/trace/trace_events_hist.c
    > @@ -1589,7 +1589,9 @@ static void __destroy_hist_field(struct hist_field *hist_field)
    >
    > kfree(hist_field->var.name);
    > kfree(hist_field->name);
    > - kfree(hist_field->type);
    > +
    > + /* Can likely be a const */
    > + kfree_const(hist_field->type);
    >
    > kfree(hist_field->system);
    > kfree(hist_field->event_name);
    > @@ -1646,9 +1648,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
    > if (flags & HIST_FIELD_FL_HITCOUNT) {
    > hist_field->fn = hist_field_counter;
    > hist_field->size = sizeof(u64);
    > - hist_field->type = kstrdup("u64", GFP_KERNEL);
    > - if (!hist_field->type)
    > - goto free;
    > + hist_field->type = "u64";
    > goto out;
    > }
    >
    > @@ -1662,7 +1662,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
    > hist_field->fn = hist_field_log2;
    > hist_field->operands[0] = create_hist_field(hist_data, field, fl, NULL);
    > hist_field->size = hist_field->operands[0]->size;
    > - hist_field->type = kstrdup(hist_field->operands[0]->type, GFP_KERNEL);
    > + hist_field->type = kstrdup_const(hist_field->operands[0]->type, GFP_KERNEL);
    > if (!hist_field->type)
    > goto free;
    > goto out;
    > @@ -1671,18 +1671,14 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
    > if (flags & HIST_FIELD_FL_TIMESTAMP) {
    > hist_field->fn = hist_field_timestamp;
    > hist_field->size = sizeof(u64);
    > - hist_field->type = kstrdup("u64", GFP_KERNEL);
    > - if (!hist_field->type)
    > - goto free;
    > + hist_field->type = "u64";
    > goto out;
    > }
    >
    > if (flags & HIST_FIELD_FL_CPU) {
    > hist_field->fn = hist_field_cpu;
    > hist_field->size = sizeof(int);
    > - hist_field->type = kstrdup("unsigned int", GFP_KERNEL);
    > - if (!hist_field->type)
    > - goto free;
    > + hist_field->type = "unsigned int";
    > goto out;
    > }
    >
    > @@ -1695,7 +1691,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
    > flags |= HIST_FIELD_FL_STRING;
    >
    > hist_field->size = MAX_FILTER_STR_VAL;
    > - hist_field->type = kstrdup(field->type, GFP_KERNEL);
    > + hist_field->type = kstrdup_const(field->type, GFP_KERNEL);
    > if (!hist_field->type)
    > goto free;
    >
    > @@ -1708,7 +1704,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
    > } else {
    > hist_field->size = field->size;
    > hist_field->is_signed = field->is_signed;
    > - hist_field->type = kstrdup(field->type, GFP_KERNEL);
    > + hist_field->type = kstrdup_const(field->type, GFP_KERNEL);
    > if (!hist_field->type)
    > goto free;
    >
    > @@ -1794,7 +1790,7 @@ static int init_var_ref(struct hist_field *ref_field,
    > }
    > }
    >
    > - ref_field->type = kstrdup(var_field->type, GFP_KERNEL);
    > + ref_field->type = kstrdup_const(var_field->type, GFP_KERNEL);
    > if (!ref_field->type) {
    > err = -ENOMEM;
    > goto free;
    > @@ -2163,7 +2159,7 @@ static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
    > expr->operands[0] = operand1;
    > expr->operator = FIELD_OP_UNARY_MINUS;
    > expr->name = expr_str(expr, 0);
    > - expr->type = kstrdup(operand1->type, GFP_KERNEL);
    > + expr->type = kstrdup_const(operand1->type, GFP_KERNEL);
    > if (!expr->type) {
    > ret = -ENOMEM;
    > goto free;
    > @@ -2289,7 +2285,7 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
    > expr->operands[1] = operand2;
    > expr->operator = field_op;
    > expr->name = expr_str(expr, 0);
    > - expr->type = kstrdup(operand1->type, GFP_KERNEL);
    > + expr->type = kstrdup_const(operand1->type, GFP_KERNEL);
    > if (!expr->type) {
    > ret = -ENOMEM;
    > goto free;
    > @@ -2677,10 +2673,10 @@ static struct hist_field *create_var(struct hist_trigger_data *hist_data,
    > var->var.hist_data = var->hist_data = hist_data;
    > var->size = size;
    > var->var.name = kstrdup(name, GFP_KERNEL);
    > - var->type = kstrdup(type, GFP_KERNEL);
    > + var->type = kstrdup_const(type, GFP_KERNEL);
    > if (!var->var.name || !var->type) {
    > + kfree_const(var->type);
    > kfree(var->var.name);
    > - kfree(var->type);
    > kfree(var);
    > var = ERR_PTR(-ENOMEM);
    > }
    > --
    > 2.30.2


    --
    Masami Hiramatsu <mhiramat@kernel.org>

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