Commit 98c4fd04 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

tracing: Keep track of set_ftrace_filter position and allow lseek again 



This patch keeps track of the index within the elements of
set_ftrace_filter and if the position goes backwards, it nicely
resets and starts from the beginning again.

This allows for lseek and pread to work properly now.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 4aeb6967

kernel/trace/ftrace.c

+26 −8
Original line number Diff line number Diff line
@@ -1368,6 +1368,7 @@ enum { 
#define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */



struct ftrace_iterator {

	loff_t				pos;

	loff_t				func_pos;

	struct ftrace_page		*pg;

	struct dyn_ftrace		*func;
@@ -1385,9 +1386,8 @@ t_hash_next(struct seq_file *m, loff_t *pos) 
	struct hlist_node *hnd = NULL;

	struct hlist_head *hhd;



	WARN_ON(!(iter->flags & FTRACE_ITER_HASH));



	(*pos)++;

	iter->pos = *pos;



	if (iter->probe)

		hnd = &iter->probe->node;
@@ -1427,14 +1427,9 @@ static void *t_hash_start(struct seq_file *m, loff_t *pos) 
	void *p = NULL;

	loff_t l;



	if (!(iter->flags & FTRACE_ITER_HASH))

		iter->func_pos = *pos;



	if (iter->func_pos > *pos)

		return NULL;



	iter->flags |= FTRACE_ITER_HASH;



	iter->hidx = 0;

	for (l = 0; l <= (*pos - iter->func_pos); ) {

		p = t_hash_next(m, &l);
@@ -1444,6 +1439,9 @@ static void *t_hash_start(struct seq_file *m, loff_t *pos) 
	if (!p)

		return NULL;



	/* Only set this if we have an item */

	iter->flags |= FTRACE_ITER_HASH;



	return iter;

}
@@ -1478,6 +1476,8 @@ t_next(struct seq_file *m, void *v, loff_t *pos) 
		return t_hash_next(m, pos);



	(*pos)++;

	iter->pos = *pos;

	iter->func_pos = *pos;



	if (iter->flags & FTRACE_ITER_PRINTALL)

		return NULL;
@@ -1517,6 +1517,13 @@ t_next(struct seq_file *m, void *v, loff_t *pos) 
	return iter;

}



static void reset_iter_read(struct ftrace_iterator *iter)

{

	iter->pos = 0;

	iter->func_pos = 0;

	iter->flags &= ~(FTRACE_ITER_PRINTALL & FTRACE_ITER_HASH);

}



static void *t_start(struct seq_file *m, loff_t *pos)

{

	struct ftrace_iterator *iter = m->private;
@@ -1524,6 +1531,12 @@ static void *t_start(struct seq_file *m, loff_t *pos) 
	loff_t l;



	mutex_lock(&ftrace_lock);

	/*

	 * If an lseek was done, then reset and start from beginning.

	 */

	if (*pos < iter->pos)

		reset_iter_read(iter);



	/*

	 * For set_ftrace_filter reading, if we have the filter

	 * off, we can short cut and just print out that all
@@ -1541,6 +1554,11 @@ static void *t_start(struct seq_file *m, loff_t *pos) 
	if (iter->flags & FTRACE_ITER_HASH)

		return t_hash_start(m, pos);



	/*

	 * Unfortunately, we need to restart at ftrace_pages_start

	 * every time we let go of the ftrace_mutex. This is because

	 * those pointers can change without the lock.

	 */

	iter->pg = ftrace_pages_start;

	iter->idx = 0;

	for (l = 0; l <= *pos; ) {
@@ -2447,7 +2465,7 @@ static const struct file_operations ftrace_filter_fops = { 
	.open = ftrace_filter_open,

	.read = seq_read,

	.write = ftrace_filter_write,

	.llseek = no_llseek,

	.llseek = ftrace_regex_lseek,

	.release = ftrace_filter_release,

};

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