Commit 74d6f030 authored by Xiubo Li's avatar Xiubo Li Committed by Ilya Dryomov
Browse files

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: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 6b0a8774

fs/ceph/mdsmap.c

+7 −4
Original line number Diff line number Diff line
@@ -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;

}