Commit a84cd293 authored Apr 09, 2013 by Sam Lang Committed by Sage Weil May 01, 2013

ceph: Use pseudo-random numbers to choose mds

We don't need to use up entropy to choose an mds,
so use prandom_u32() to get a pseudo-random number.

Also, we don't need to choose a random mds if only
one mds is available, so add special casing for the
common case.

Fixes http://tracker.ceph.com/issues/3579



Signed-off-by: Sam Lang <sam.lang@inktank.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>

parent 8b3e1a56

fs/ceph/mdsmap.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -20,7 +20,10 @@ int ceph_mdsmap_get_random_mds(struct ceph_mdsmap *m)
		{
		int n = 0;
		int i;
		char r;

		/* special case for one mds */
		if (1 == m->m_max_mds && m->m_info[0].state > 0)
		return 0;

		/* count */
		for (i = 0; i < m->m_max_mds; i++)
		@@ -30,8 +33,7 @@ int ceph_mdsmap_get_random_mds(struct ceph_mdsmap *m)
		return -1;

		/* pick */
		get_random_bytes(&r, 1);
		n = r % n;
		n = prandom_u32() % n;
		i = 0;
		for (i = 0; n > 0; i++, n--)
		while (m->m_info[i].state <= 0)

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