GFS2: Use RCU for glock hash table
This has a number of advantages:
- Reduces contention on the hash table lock
- Makes the code smaller and simpler
- Should speed up glock dumps when under load
- Removes ref count changing in examine_bucket
- No longer need hash chain lock in glock_put() in common case
There are some further changes which this enables and which
we may do in the future. One is to look at using SLAB_RCU,
and another is to look at using a per-cpu counter for the
per-sb glock counter, since that is touched twice in the
lifetime of each glock (but only used at umount time).
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index 6e493ae..c80485c 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -22,7 +22,6 @@
{
struct gfs2_glock *gl = arg;
unsigned ret = gl->gl_state;
- struct gfs2_sbd *sdp = gl->gl_sbd;
BUG_ON(gl->gl_lksb.sb_flags & DLM_SBF_DEMOTED);
@@ -31,12 +30,7 @@
switch (gl->gl_lksb.sb_status) {
case -DLM_EUNLOCK: /* Unlocked, so glock can be freed */
- if (gl->gl_ops->go_flags & GLOF_ASPACE)
- kmem_cache_free(gfs2_glock_aspace_cachep, gl);
- else
- kmem_cache_free(gfs2_glock_cachep, gl);
- if (atomic_dec_and_test(&sdp->sd_glock_disposal))
- wake_up(&sdp->sd_glock_wait);
+ call_rcu(&gl->gl_rcu, gfs2_glock_free);
return;
case -DLM_ECANCEL: /* Cancel while getting lock */
ret |= LM_OUT_CANCELED;
@@ -164,16 +158,14 @@
GDLM_STRNAME_BYTES - 1, 0, gdlm_ast, gl, gdlm_bast);
}
-static void gdlm_put_lock(struct kmem_cache *cachep, struct gfs2_glock *gl)
+static void gdlm_put_lock(struct gfs2_glock *gl)
{
struct gfs2_sbd *sdp = gl->gl_sbd;
struct lm_lockstruct *ls = &sdp->sd_lockstruct;
int error;
if (gl->gl_lksb.sb_lkid == 0) {
- kmem_cache_free(cachep, gl);
- if (atomic_dec_and_test(&sdp->sd_glock_disposal))
- wake_up(&sdp->sd_glock_wait);
+ call_rcu(&gl->gl_rcu, gfs2_glock_free);
return;
}