cpufreq: stats: Handle the case when trans_table goes beyond PAGE_SIZE
On platforms with large number of Pstates, the transition table, which
is a NxN matrix, can overflow beyond the PAGE_SIZE boundary.
This can be seen on POWER9 which has 100+ Pstates.
As a result, each time the trans_table is read for any of the CPUs, we
will get the following error.
---------------------------------------------------
fill_read_buffer: show+0x0/0xa0 returned bad count
---------------------------------------------------
This patch ensures that in case of an overflow, we print a warning
once in the dmesg and return FILE TOO LARGE error for this and all
subsequent accesses of trans_table.
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index e75880e..1e55b57 100644
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -118,8 +118,11 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
break;
len += snprintf(buf + len, PAGE_SIZE - len, "\n");
}
- if (len >= PAGE_SIZE)
- return PAGE_SIZE;
+
+ if (len >= PAGE_SIZE) {
+ pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n");
+ return -EFBIG;
+ }
return len;
}
cpufreq_freq_attr_ro(trans_table);