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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: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2010-09-10 11:47:43 -04:00 committed by Steven Rostedt
parent 4aeb69672d
commit 98c4fd046f
1 changed files with 26 additions and 8 deletions
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34
kernel/trace/ftrace.c
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@ -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,
};