tracing/filter: Use a tree instead of stack for filter_match_preds()
Currently the filter_match_preds() requires a stack to push
and pop the preds to determine if the filter matches the record or not.
This has two drawbacks:
1) It requires a stack to store state information. As this is done
in fast paths we can't allocate the storage for this stack, and
we can't use a global as it must be re-entrant. The stack is stored
on the kernel stack and this greatly limits how many preds we
may allow.
2) All conditions are calculated even when a short circuit exists.
a || b will always calculate a and b even though a was determined
to be true.
Using a tree we can walk a constant structure that will save
the state as we go. The algorithm is simply:
pred = root;
do {
switch (move) {
case MOVE_DOWN:
if (OR or AND) {
pred = left;
continue;
}
if (pred == root)
break;
match = pred->fn();
pred = pred->parent;
move = left child ? MOVE_UP_FROM_LEFT : MOVE_UP_FROM_RIGHT;
continue;
case MOVE_UP_FROM_LEFT:
/* Only OR or AND can be a parent */
if (match && OR || !match && AND) {
/* short circuit */
if (pred == root)
break;
pred = pred->parent;
move = left child ?
MOVE_UP_FROM_LEFT :
MOVE_UP_FROM_RIGHT;
continue;
}
pred = pred->right;
move = MOVE_DOWN;
continue;
case MOVE_UP_FROM_RIGHT:
if (pred == root)
break;
pred = pred->parent;
move = left child ? MOVE_UP_FROM_LEFT : MOVE_UP_FROM_RIGHT;
continue;
}
done = 1;
} while (!done);
This way there's no strict limit to how many preds we allow
and it also will short circuit the logical operations when possible.
Cc: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt
Steven Rostedt
parent
f76690afd0
commit
61e9dea20e
@ -664,6 +664,7 @@ struct event_filter {
|
||||
int n_preds; /* Number assigned */
|
||||
int a_preds; /* allocated */
|
||||
struct filter_pred *preds;
|
||||
struct filter_pred *root;
|
||||
char *filter_string;
|
||||
};
|
||||
|
||||
@ -675,6 +676,9 @@ struct event_subsystem {
|
||||
int nr_events;
|
||||
};
|
||||
|
||||
#define FILTER_PRED_INVALID ((unsigned short)-1)
|
||||
#define FILTER_PRED_IS_RIGHT (1 << 15)
|
||||
|
||||
struct filter_pred;
|
||||
struct regex;
|
||||
|
||||
@ -704,7 +708,10 @@ struct filter_pred {
|
||||
int offset;
|
||||
int not;
|
||||
int op;
|
||||
int pop_n;
|
||||
unsigned short index;
|
||||
unsigned short parent;
|
||||
unsigned short left;
|
||||
unsigned short right;
|
||||
};
|
||||
|
||||
extern struct list_head ftrace_common_fields;
|
||||
|
||||
@ -123,6 +123,11 @@ struct filter_parse_state {
|
||||
} operand;
|
||||
};
|
||||
|
||||
struct pred_stack {
|
||||
struct filter_pred **preds;
|
||||
int index;
|
||||
};
|
||||
|
||||
#define DEFINE_COMPARISON_PRED(type) \
|
||||
static int filter_pred_##type(struct filter_pred *pred, void *event) \
|
||||
{ \
|
||||
@ -357,52 +362,95 @@ static void filter_build_regex(struct filter_pred *pred)
|
||||
pred->not ^= not;
|
||||
}
|
||||
|
||||
enum move_type {
|
||||
MOVE_DOWN,
|
||||
MOVE_UP_FROM_LEFT,
|
||||
MOVE_UP_FROM_RIGHT
|
||||
};
|
||||
|
||||
static struct filter_pred *
|
||||
get_pred_parent(struct filter_pred *pred, struct filter_pred *preds,
|
||||
int index, enum move_type *move)
|
||||
{
|
||||
if (pred->parent & FILTER_PRED_IS_RIGHT)
|
||||
*move = MOVE_UP_FROM_RIGHT;
|
||||
else
|
||||
*move = MOVE_UP_FROM_LEFT;
|
||||
pred = &preds[pred->parent & ~FILTER_PRED_IS_RIGHT];
|
||||
|
||||
return pred;
|
||||
}
|
||||
|
||||
/* return 1 if event matches, 0 otherwise (discard) */
|
||||
int filter_match_preds(struct event_filter *filter, void *rec)
|
||||
{
|
||||
int match = -1, top = 0, val1 = 0, val2 = 0;
|
||||
int stack[MAX_FILTER_PRED];
|
||||
int match = -1;
|
||||
enum move_type move = MOVE_DOWN;
|
||||
struct filter_pred *preds;
|
||||
struct filter_pred *pred;
|
||||
struct filter_pred *root;
|
||||
int n_preds = ACCESS_ONCE(filter->n_preds);
|
||||
int i;
|
||||
int done = 0;
|
||||
|
||||
/* no filter is considered a match */
|
||||
if (!n_preds)
|
||||
return 1;
|
||||
|
||||
/*
|
||||
* n_preds and filter->preds is protect with preemption disabled.
|
||||
* n_preds, root and filter->preds are protect with preemption disabled.
|
||||
*/
|
||||
preds = rcu_dereference_sched(filter->preds);
|
||||
root = rcu_dereference_sched(filter->root);
|
||||
if (!root)
|
||||
return 1;
|
||||
|
||||
for (i = 0; i < n_preds; i++) {
|
||||
pred = &preds[i];
|
||||
if (!pred->pop_n) {
|
||||
pred = root;
|
||||
|
||||
/* match is currently meaningless */
|
||||
match = -1;
|
||||
|
||||
do {
|
||||
switch (move) {
|
||||
case MOVE_DOWN:
|
||||
/* only AND and OR have children */
|
||||
if (pred->left != FILTER_PRED_INVALID) {
|
||||
/* keep going to leaf node */
|
||||
pred = &preds[pred->left];
|
||||
continue;
|
||||
}
|
||||
match = pred->fn(pred, rec);
|
||||
stack[top++] = match;
|
||||
/* If this pred is the only pred */
|
||||
if (pred == root)
|
||||
break;
|
||||
pred = get_pred_parent(pred, preds,
|
||||
pred->parent, &move);
|
||||
continue;
|
||||
case MOVE_UP_FROM_LEFT:
|
||||
/* Check for short circuits */
|
||||
if ((match && pred->op == OP_OR) ||
|
||||
(!match && pred->op == OP_AND)) {
|
||||
if (pred == root)
|
||||
break;
|
||||
pred = get_pred_parent(pred, preds,
|
||||
pred->parent, &move);
|
||||
continue;
|
||||
}
|
||||
/* now go down the right side of the tree. */
|
||||
pred = &preds[pred->right];
|
||||
move = MOVE_DOWN;
|
||||
continue;
|
||||
case MOVE_UP_FROM_RIGHT:
|
||||
/* We finished this equation. */
|
||||
if (pred == root)
|
||||
break;
|
||||
pred = get_pred_parent(pred, preds,
|
||||
pred->parent, &move);
|
||||
continue;
|
||||
}
|
||||
if (pred->pop_n > top) {
|
||||
WARN_ON_ONCE(1);
|
||||
return 0;
|
||||
}
|
||||
val1 = stack[--top];
|
||||
val2 = stack[--top];
|
||||
switch (pred->op) {
|
||||
case OP_AND:
|
||||
match = val1 && val2;
|
||||
break;
|
||||
case OP_OR:
|
||||
match = val1 || val2;
|
||||
break;
|
||||
default:
|
||||
WARN_ONCE(1, "filter op is not AND or OR");
|
||||
}
|
||||
stack[top++] = match;
|
||||
}
|
||||
done = 1;
|
||||
} while (!done);
|
||||
|
||||
return stack[--top];
|
||||
return match;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(filter_match_preds);
|
||||
|
||||
@ -539,10 +587,58 @@ static void filter_clear_pred(struct filter_pred *pred)
|
||||
pred->regex.len = 0;
|
||||
}
|
||||
|
||||
static int filter_set_pred(struct filter_pred *dest,
|
||||
static int __alloc_pred_stack(struct pred_stack *stack, int n_preds)
|
||||
{
|
||||
stack->preds = kzalloc(sizeof(*stack->preds)*(n_preds + 1), GFP_KERNEL);
|
||||
if (!stack->preds)
|
||||
return -ENOMEM;
|
||||
stack->index = n_preds;
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void __free_pred_stack(struct pred_stack *stack)
|
||||
{
|
||||
kfree(stack->preds);
|
||||
stack->index = 0;
|
||||
}
|
||||
|
||||
static int __push_pred_stack(struct pred_stack *stack,
|
||||
struct filter_pred *pred)
|
||||
{
|
||||
int index = stack->index;
|
||||
|
||||
if (WARN_ON(index == 0))
|
||||
return -ENOSPC;
|
||||
|
||||
stack->preds[--index] = pred;
|
||||
stack->index = index;
|
||||
return 0;
|
||||
}
|
||||
|
||||
static struct filter_pred *
|
||||
__pop_pred_stack(struct pred_stack *stack)
|
||||
{
|
||||
struct filter_pred *pred;
|
||||
int index = stack->index;
|
||||
|
||||
pred = stack->preds[index++];
|
||||
if (!pred)
|
||||
return NULL;
|
||||
|
||||
stack->index = index;
|
||||
return pred;
|
||||
}
|
||||
|
||||
static int filter_set_pred(struct event_filter *filter,
|
||||
int idx,
|
||||
struct pred_stack *stack,
|
||||
struct filter_pred *src,
|
||||
filter_pred_fn_t fn)
|
||||
{
|
||||
struct filter_pred *dest = &filter->preds[idx];
|
||||
struct filter_pred *left;
|
||||
struct filter_pred *right;
|
||||
|
||||
*dest = *src;
|
||||
if (src->field_name) {
|
||||
dest->field_name = kstrdup(src->field_name, GFP_KERNEL);
|
||||
@ -550,8 +646,25 @@ static int filter_set_pred(struct filter_pred *dest,
|
||||
return -ENOMEM;
|
||||
}
|
||||
dest->fn = fn;
|
||||
dest->index = idx;
|
||||
|
||||
return 0;
|
||||
if (dest->op == OP_OR || dest->op == OP_AND) {
|
||||
right = __pop_pred_stack(stack);
|
||||
left = __pop_pred_stack(stack);
|
||||
if (!left || !right)
|
||||
return -EINVAL;
|
||||
dest->left = left->index;
|
||||
dest->right = right->index;
|
||||
left->parent = dest->index;
|
||||
right->parent = dest->index | FILTER_PRED_IS_RIGHT;
|
||||
} else
|
||||
/*
|
||||
* Make dest->left invalid to be used as a quick
|
||||
* way to know this is a leaf node.
|
||||
*/
|
||||
dest->left = FILTER_PRED_INVALID;
|
||||
|
||||
return __push_pred_stack(stack, dest);
|
||||
}
|
||||
|
||||
static void __free_preds(struct event_filter *filter)
|
||||
@ -574,6 +687,7 @@ static void reset_preds(struct event_filter *filter)
|
||||
int i;
|
||||
|
||||
filter->n_preds = 0;
|
||||
filter->root = NULL;
|
||||
if (!filter->preds)
|
||||
return;
|
||||
|
||||
@ -707,6 +821,7 @@ static int filter_add_pred_fn(struct filter_parse_state *ps,
|
||||
struct ftrace_event_call *call,
|
||||
struct event_filter *filter,
|
||||
struct filter_pred *pred,
|
||||
struct pred_stack *stack,
|
||||
filter_pred_fn_t fn)
|
||||
{
|
||||
int idx, err;
|
||||
@ -718,7 +833,7 @@ static int filter_add_pred_fn(struct filter_parse_state *ps,
|
||||
|
||||
idx = filter->n_preds;
|
||||
filter_clear_pred(&filter->preds[idx]);
|
||||
err = filter_set_pred(&filter->preds[idx], pred, fn);
|
||||
err = filter_set_pred(filter, idx, stack, pred, fn);
|
||||
if (err)
|
||||
return err;
|
||||
|
||||
@ -803,6 +918,7 @@ static int filter_add_pred(struct filter_parse_state *ps,
|
||||
struct ftrace_event_call *call,
|
||||
struct event_filter *filter,
|
||||
struct filter_pred *pred,
|
||||
struct pred_stack *stack,
|
||||
bool dry_run)
|
||||
{
|
||||
struct ftrace_event_field *field;
|
||||
@ -812,13 +928,10 @@ static int filter_add_pred(struct filter_parse_state *ps,
|
||||
|
||||
fn = pred->fn = filter_pred_none;
|
||||
|
||||
if (pred->op == OP_AND) {
|
||||
pred->pop_n = 2;
|
||||
if (pred->op == OP_AND)
|
||||
goto add_pred_fn;
|
||||
} else if (pred->op == OP_OR) {
|
||||
pred->pop_n = 2;
|
||||
else if (pred->op == OP_OR)
|
||||
goto add_pred_fn;
|
||||
}
|
||||
|
||||
field = find_event_field(call, pred->field_name);
|
||||
if (!field) {
|
||||
@ -867,7 +980,7 @@ static int filter_add_pred(struct filter_parse_state *ps,
|
||||
|
||||
add_pred_fn:
|
||||
if (!dry_run)
|
||||
return filter_add_pred_fn(ps, call, filter, pred, fn);
|
||||
return filter_add_pred_fn(ps, call, filter, pred, stack, fn);
|
||||
return 0;
|
||||
}
|
||||
|
||||
@ -1248,6 +1361,7 @@ static int replace_preds(struct ftrace_event_call *call,
|
||||
char *operand1 = NULL, *operand2 = NULL;
|
||||
struct filter_pred *pred;
|
||||
struct postfix_elt *elt;
|
||||
struct pred_stack stack = { }; /* init to NULL */
|
||||
int err;
|
||||
int n_preds = 0;
|
||||
|
||||
@ -1262,9 +1376,12 @@ static int replace_preds(struct ftrace_event_call *call,
|
||||
return err;
|
||||
|
||||
if (!dry_run) {
|
||||
err = __alloc_preds(filter, n_preds);
|
||||
err = __alloc_pred_stack(&stack, n_preds);
|
||||
if (err)
|
||||
return err;
|
||||
err = __alloc_preds(filter, n_preds);
|
||||
if (err)
|
||||
goto fail;
|
||||
}
|
||||
|
||||
n_preds = 0;
|
||||
@ -1276,14 +1393,16 @@ static int replace_preds(struct ftrace_event_call *call,
|
||||
operand2 = elt->operand;
|
||||
else {
|
||||
parse_error(ps, FILT_ERR_TOO_MANY_OPERANDS, 0);
|
||||
return -EINVAL;
|
||||
err = -EINVAL;
|
||||
goto fail;
|
||||
}
|
||||
continue;
|
||||
}
|
||||
|
||||
if (WARN_ON(n_preds++ == MAX_FILTER_PRED)) {
|
||||
parse_error(ps, FILT_ERR_TOO_MANY_PREDS, 0);
|
||||
return -ENOSPC;
|
||||
err = -ENOSPC;
|
||||
goto fail;
|
||||
}
|
||||
|
||||
if (elt->op == OP_AND || elt->op == OP_OR) {
|
||||
@ -1293,22 +1412,44 @@ static int replace_preds(struct ftrace_event_call *call,
|
||||
|
||||
if (!operand1 || !operand2) {
|
||||
parse_error(ps, FILT_ERR_MISSING_FIELD, 0);
|
||||
return -EINVAL;
|
||||
err = -EINVAL;
|
||||
goto fail;
|
||||
}
|
||||
|
||||
pred = create_pred(elt->op, operand1, operand2);
|
||||
add_pred:
|
||||
if (!pred)
|
||||
return -ENOMEM;
|
||||
err = filter_add_pred(ps, call, filter, pred, dry_run);
|
||||
if (!pred) {
|
||||
err = -ENOMEM;
|
||||
goto fail;
|
||||
}
|
||||
err = filter_add_pred(ps, call, filter, pred, &stack, dry_run);
|
||||
filter_free_pred(pred);
|
||||
if (err)
|
||||
return err;
|
||||
goto fail;
|
||||
|
||||
operand1 = operand2 = NULL;
|
||||
}
|
||||
|
||||
return 0;
|
||||
if (!dry_run) {
|
||||
/* We should have one item left on the stack */
|
||||
pred = __pop_pred_stack(&stack);
|
||||
if (!pred)
|
||||
return -EINVAL;
|
||||
/* This item is where we start from in matching */
|
||||
filter->root = pred;
|
||||
/* Make sure the stack is empty */
|
||||
pred = __pop_pred_stack(&stack);
|
||||
if (WARN_ON(pred)) {
|
||||
err = -EINVAL;
|
||||
filter->root = NULL;
|
||||
goto fail;
|
||||
}
|
||||
}
|
||||
|
||||
err = 0;
|
||||
fail:
|
||||
__free_pred_stack(&stack);
|
||||
return err;
|
||||
}
|
||||
|
||||
static int replace_system_preds(struct event_subsystem *system,
|
||||
|
||||
Loading…
Reference in New Issue
Block a user