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cpufreq: stats: Handle the case when trans_table goes beyond PAGE_SIZE

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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>
This commit is contained in:
Gautham R. Shenoy
2017-11-07 13:39:29 +05:30
committed by Rafael J. Wysocki
parent 0011c6da99
commit f7bc9b209e
2 changed files with 8 additions and 2 deletions
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7
drivers/cpufreq/cpufreq_stats.c
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@@ -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);