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ceph: fix geting random mds from mdsmap 

For example, if we have 5 mds in the mdsmap and the states are:
m_info[5] --> [-1, 1, -1, 1, 1]

If we get a random number 1, then we should get the mds index 3 as
expected, but actually we will get index 2, which the state is -1.

The issue is that the for loop increment will advance past any "up"
MDS that was found during the while loop search.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Xiubo Li 2019-11-11 06:51:05 -05:00 committed by Ilya Dryomov
parent 6b0a877422
commit 74d6f03019
1 changed files with 7 additions and 4 deletions
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11
fs/ceph/mdsmap.c
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@ -20,7 +20,7 @@
int ceph_mdsmap_get_random_mds(struct ceph_mdsmap *m)
{
int n = 0;
int i;
int i, j;
/* special case for one mds */
if (1 == m->m_num_mds && m->m_info[0].state > 0)
@ -35,9 +35,12 @@ int ceph_mdsmap_get_random_mds(struct ceph_mdsmap *m)
/* pick */
n = prandom_u32() % n;
for (i = 0; n > 0; i++, n--)
while (m->m_info[i].state <= 0)
i++;
for (j = 0, i = 0; i < m->m_num_mds; i++) {
if (m->m_info[i].state > 0)
j++;
if (j > n)
break;
}
return i;
}