From: Jens Axboe <axboe@fb.com>
Date: Tue, 21 Apr 2015 14:25:58 +0000 (-0600)
Subject: Fix off-by-one in cpu mask index handling
X-Git-Tag: fio-2.2.8~33
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=b84113993b3aa40dc33ba101cd39a95d88732811

Fix off-by-one in cpu mask index handling

This just affects how errors are printed. Kleber Sacilotto de Souza
reports:

The error message displayed by the option parser for the 'cpus_allowed'
parameter is misleading.

My system has 4 processors:

$ grep -c processor /proc/cpuinfo
4

If I provide a high number for cpus_allowed, I get the error message:

$ fio --filename=/tmp/foo.fio --cpus_allowed=5 --name=job1
fio: CPU 5 too large (max=4)
fio: failed parsing cpus_allowed=5

If it says "(max=4)", I would expect it to accept the value "4" if I
want to use the last CPU of the system (even though we know that the
CPUs are generally numbered starting with 0), but that's not what
happens:

$ fio --name=global --filename=/tmp/foo.fio --cpus_allowed=4 --name=job1
job1: (g=0): rw=read, bs=4K-4K/4K-4K/4K-4K, ioengine=sync, iodepth=1
fio-2.1.3
Starting 1 process
fio: pid=24942, err=22/file:backend.c:1192, func=cpu_set_affinity, error=Invalid argument

So for setting the affinity the CPU number really starts from 0, so 3
would be the right value in this case and the following command works as
expected:

Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/options.c b/options.c
index 017920e1..b5195c35 100644
--- a/options.c
+++ b/options.c
@@ -443,9 +443,9 @@ static int str_cpumask_cb(void *data, unsigned long long *val)
 
 	for (i = 0; i < sizeof(int) * 8; i++) {
 		if ((1 << i) & *val) {
-			if (i > max_cpu) {
+			if (i >= max_cpu) {
 				log_err("fio: CPU %d too large (max=%ld)\n", i,
-								max_cpu);
+								max_cpu - 1);
 				return 1;
 			}
 			dprint(FD_PARSE, "set cpu allowed %d\n", i);