Use the reentrant getmntent_r instead of getmntent

The function find_cgroup_mnt() could be called under multithread scenario, so
we should use the reentrant edition getmntent_r() instead of getmntent().

E.g, without this fix the output for below job file is wrong.

[root@localhost blkio-test]# cat small-read-file
[global]
ioengine=sync
direct=1
rw=read
bs=4k
filename=/dev/sdb
time_based
runtime=60
cgroup=small
cgroup_weight=500
numjobs=32
group_reporting
thread

[file1]

Then fio randomly says:
[cut here]
Starting 32 threads
fio: cgroup blkio does not appear to be mounted
fio: cgroup blkio does not appear to be mounted
fio: cgroup blkio does not appear to be mounted

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/cgroup.c b/cgroup.c
index f36683aeacf311561c6ba768565361c547fcd9bf..de00d986eb05246b25e853c3af524149f1b53e22 100644 (file)
--- a/cgroup.c
+++ b/cgroup.c
@@ -22,7 +22,8 @@ struct cgroup_member {
 static char *find_cgroup_mnt(struct thread_data *td)
 {
        char *mntpoint = NULL;
-       struct mntent *mnt;
+       struct mntent *mnt, dummy;
+       char buf[256] = {0};
        FILE *f;
 
        f = setmntent("/proc/mounts", "r");
@@ -31,7 +32,7 @@ static char *find_cgroup_mnt(struct thread_data *td)
                return NULL;
        }
 
-       while ((mnt = getmntent(f)) != NULL) {
+       while ((mnt = getmntent_r(f, &dummy, buf, sizeof(buf))) != NULL) {
                if (!strcmp(mnt->mnt_type, "cgroup") &&
                    strstr(mnt->mnt_opts, "blkio"))
                        break;