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authorSam Lang <sam.lang@inktank.com>2013-04-09 23:49:11 +0200
committerSage Weil <sage@inktank.com>2013-05-02 06:18:49 +0200
commita84cd29335f4ca38ca8405c1636ee3876bb292b5 (patch)
tree953fdc6edc1ae9374f59a25c8892d2ce0d662058 /fs/ceph/mdsmap.c
parentrbd: implement layered reads (diff)
downloadlinux-a84cd29335f4ca38ca8405c1636ee3876bb292b5.tar.xz
linux-a84cd29335f4ca38ca8405c1636ee3876bb292b5.zip
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>
Diffstat (limited to 'fs/ceph/mdsmap.c')
-rw-r--r--fs/ceph/mdsmap.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
index 0d3c9240c61b..9278dec9e940 100644
--- a/fs/ceph/mdsmap.c
+++ b/fs/ceph/mdsmap.c
@@ -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)